Publications by authors named "Shuo Jiao"

69 Publications

Stochastic community assembly decreases soil fungal richness in arid ecosystems.

Mol Ecol 2021 Jun 29. Epub 2021 Jun 29.

State Key Laboratory of Crop Stress Biology in Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China.

Uncovering the linkages between community assembly and species diversity is a fundamental issue in microbial ecology. In this study, a large-scale (transect intervals of 1257.6 km) cross-biome soil survey was conducted, which ranged over agricultural fields, forests, wetlands, grasslands and desert, in the arid regions of northwest China. The aim was to investigate the biogeographic distribution, community assembly and species co-occurrence of soil fungi. The fungal communities in agricultural soils exhibited a steeper distance-decay slope and wider niche breadths, and were more strongly affected by stochastic assembly processes, than fungi in other natural habitats. A strong relationship was revealed between soil fungal richness and community assembly in arid ecosystems, with the influence of stochastic assembly processes decreasing with increasing fungal richness. Moreover, aridity was the most important environmental factor influencing fungal richness, β-diversity and species co-occurrence patterns. Specifically, the predicted increase in arid conditions will probably reduce fungal richness and network complexity. These findings represent a considerable advance in linking fungal richness to mechanisms underlying the biogeographic patterns and assembly processes of fungal communities in arid ecosystems. These results can thus be used to forecast species co-occurrence and diversities pattern of soil fungi under climate aridity and land-use change scenarios.
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http://dx.doi.org/10.1111/mec.16047DOI Listing
June 2021

Thermodynamics shapes the biogeography of propionate-oxidizing syntrophs in paddy field soils.

Environ Microbiol Rep 2021 Jun 4. Epub 2021 Jun 4.

College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China.

Soil biogeochemical processes are not only gauged by the dominant taxa in the microbiome but also depend on the critical functions of its 'rare biosphere' members. Here, we evaluated the biogeographical pattern of 'rare biosphere' propionate-oxidizing syntrophs in 113 paddy soil samples collected across China. The relative abundance, activity and growth potential of propionate-oxidizing syntrophs were analysed to provide a panoramic view of syntroph biogeographical distribution at the continental scale. The relative abundances of four syntroph genera, Syntrophobacter, Pelotomaculum, Smithella and Syntrophomonas were significantly greater at the warm low latitudes than at the cool high latitudes. Correspondingly, propionate degradation was faster in the low latitude soils compared with the high latitude soils. The low rate of propionate degradation in the high latitude soils resulted in a greater increase of the total syntroph relative abundance, probably due to their initial low relative abundances and the longer incubation time for propionate consumption. The mean annual temperature (MAT) is the most important factor shaping the biogeographical pattern of propionate-oxidizing syntrophs, with the next factor being the soil's total sulfur content (TS). We suggest that the effect of MAT is related to the thermodynamic conditions, in which the endergonic constraint of propionate oxidation is leveraged with the increase of MAT. The TS effect is likely due to the ability of some propionate syntrophs to facultatively perform sulfate respiration.
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http://dx.doi.org/10.1111/1758-2229.12981DOI Listing
June 2021

Linking Bacterial-Fungal Relationships to Microbial Diversity and Soil Nutrient Cycling.

mSystems 2021 Mar 23;6(2). Epub 2021 Mar 23.

State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, People's Republic of China

Biodiversity is important for supporting ecosystem functioning. To evaluate the factors contributing to the strength of microbial diversity-function relationships in complex terrestrial ecosystems, we conducted a soil survey over different habitats, including an agricultural field, forest, wetland, grassland, and desert. Soil microbial multidiversity was estimated by the combination of bacterial and fungal diversity. Soil ecosystem functions were evaluated using a multinutrient cycling index (MNC) in relation to carbon, nitrate, phosphorus, and potassium cycling. Significant positive relationships between soil multidiversity and multinutrient cycling were observed in all habitats, except the grassland and desert. Specifically, community compositions showed stronger correlations with multinutrient cycling than α-diversity, indicating the crucial role of microbial community composition differences on soil nutrient cycling. Importantly, we revealed that changes in both the neutral processes (Sloan neutral modeling) and the proportion of negative bacterial-fungal associations were linked to the magnitude and direction of the diversity-MNC relationships. The habitats less governed by neutral processes and dominated by negative bacterial-fungal associations exhibited stronger negative microbial -diversity-MNC relationships. Our findings suggested that the balance between positive and negative bacterial-fungal associations was connected to the link between soil biodiversity and ecosystem function in complex terrestrial ecosystems. This study elucidates the potential factors influencing diversity-function relationships, thereby enabling future studies to forecast the effects of belowground biodiversity on ecosystem function. The relationships between soil biodiversity and ecosystem functions are an important yet poorly understood topic in microbial ecology. This study presents an exploratory effort to gain predictive understanding of the factors driving the relationships between microbial diversity and potential soil nutrient cycling in complex terrestrial ecosystems. Our structural equation modeling and random forest analysis revealed that the balance between positive and negative bacterial-fungal associations was clearly linked to the strength of the relationships between soil microbial diversity and multiple nutrients cycling across different habitats. This study revealed the potential factors underpinning diversity-function relationships in terrestrial ecosystems and thus helps us to manage soil microbial communities for better provisioning of key ecosystem services.
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http://dx.doi.org/10.1128/mSystems.01052-20DOI Listing
March 2021

Coexistence patterns of soil methanogens are closely tied to methane generation and community assembly in rice paddies.

Microbiome 2021 01 22;9(1):20. Epub 2021 Jan 22.

State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.

Background: Soil methanogens participate in complex interactions, which determine the community structures and functions. Studies continue to seek the coexistence patterns of soil methanogens, influencing factors and the contribution to methane (CH) production, which are regulated primarily by species interactions, and the functional significance of these interactions. Here, methane emissions were measured in rice paddies across the Asian continent, and the complex interactions involved in coexistence patterns of methanogenic archaeal communities were represented as pairwise links in co-occurrence networks.

Results: The network topological properties, which were positively correlated with mean annual temperature, were the most important predictor of CH emissions among all the biotic and abiotic factors. The methanogenic groups involved in commonly co-occurring links among the 39 local networks contributed most to CH emission (53.3%), much higher than the contribution of methanogenic groups with endemic links (36.8%). The potential keystone taxa, belonging to Methanobacterium, Methanocella, Methanothrix, and Methanosarcina, possessed high linkages with the methane generation functional genes mcrA, fwdB, mtbA, and mtbC. Moreover, the commonly coexisting taxa showed a very different assembly pattern, with ~ 30% determinism and ~ 70% stochasticity. In contrast, a higher proportion of stochasticity (93~99%) characterized the assembly of endemically coexisting taxa.

Conclusions: These results suggest that the coexistence patterns of microbes are closely tied to their functional significance, and the potential importance of common coexistence further imply that complex networks of interactions may contribute more than species diversity to soil functions. Video abstract.
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http://dx.doi.org/10.1186/s40168-020-00978-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7825242PMC
January 2021

Stronger impacts of long-term relative to short-term exposure to carbon nanomaterials on soil bacterial communities.

J Hazard Mater 2021 05 12;410:124550. Epub 2020 Nov 12.

Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China. Electronic address:

Environmental impacts of carbon nanomaterials (CNMs) have been attracting increasing concerns in recent years. Knowledge on how short-term exposure to CNMs influences soil microbial communities is available. However, little is known about the possible difference in effects of long-term versus short-term exposure of CNMs on soil microbial communities. In this study, we systematically compared effects of fullerene (C), single-walled carbon nanotubes (SW), and graphene (GR) on soil bacterial communities over short (30 d) and long (360 d) term exposure durations. Our findings revealed that short-term exposure to all CNMs significantly increased the alpha diversity of soil bacterial communities. SW and GR exposure for 360 d relative to that for 30 d more significantly decreased their alpha diversity. Compared to short-term exposure, a long term exposure to CNMs more strongly altered the beta diversity of soil bacterial communities. LEfSe analysis showed that, GR relative to C and SW exposure more strongly altered soil bacterial community composition especially for long-term duration at various taxonomic levels; more taxa were also identified by LEfSe analysis as biomarkers upon long-term GR exposure. More OTUs were affected by long-term GR exposure. These differences resulted from both distinct physicochemical properties of various CNMs and their exposure durations.
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http://dx.doi.org/10.1016/j.jhazmat.2020.124550DOI Listing
May 2021

High soil pH enhances the network interactions among bacterial and archaeal microbiota in alpine grasslands of the Tibetan Plateau.

Environ Microbiol 2021 01 28;23(1):464-477. Epub 2020 Nov 28.

School of Life Sciences, Lanzhou University, Lanzhou, China.

Soil functions and processes are driven by complex microbial interactions. It is, therefore, critical to understand the coexistence patterns of soil microbiota, especially in fragile alpine ecosystems. We identified biogeographic patterns in the network-level topological features of the soil microbial co-occurrence network in the Tibetan alpine grasslands, based on high-throughput sequencing. We verified that soil pH was the most important environmental variable for predicting network-level topological features of soil microbial co-occurrence networks. Associations among soil microbiota were enhanced with increasing pH (5.17-8.92), and the network was the most stable at neutral pH. Moreover, node-level topological features suggested that the archaeal operational taxonomic units, compared with bacterial operational taxonomic units, hold a central role in the co-occurrence network. Network-level topological features revealed closer connections among soil microbiota in the steppe ecosystem than in the meadow ecosystem. Therefore, our study demonstrated that soil pH served as a critical environmental filter that influenced the potential associations and ecological signature of soil microbiota in the Tibetan alpine grasslands. These findings provide a new perspective on the distinct biogeographic patterns of co-occurrence networks, to explore the ecological role of soil microbiota and thus help manage soil bacterial and archaeal communities for provisioning alpine ecosystem services.
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http://dx.doi.org/10.1111/1462-2920.15333DOI Listing
January 2021

Soil potassium is correlated with root secondary metabolites and root-associated core bacteria in licorice of different ages.

Plant Soil 2020 Sep 3:1-19. Epub 2020 Sep 3.

State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Science, Northwest A&F University, 3 Taicheng Road, Yangling, Shaanxi 712100 People's Republic of China.

Aims: Licorice ( Fisch) is a crucial medicinal herb as it accumulates glycyrrhizin and liquiritin in roots. Licorice root-associated bacterial communities shaped by soil characteristics are supposed to regulate the accumulation of root secondary metabolites.

Methods: The soil characteristics, root secondary metabolites, and root-associated bacterial communities were analyzed in licorice plants of different ages to explore their temporal dynamics and interaction mechanisms.

Results: Temporal variation in soil characteristics and root secondary metabolites was distinct. The alpha-diversity of root-associated bacterial communities decreased with root proximity, and the community composition was clustered in the rhizosphere. Different taxa that were core-enriched from the dominant taxa in the bulk soil, rhizosphere soil, and root endosphere displayed varied time-decay relationships. Soil total potassium (TK) as a key factor regulated the temporal variation in some individual taxa in the bulk and rhizosphere soils; these taxa were associated with the adjustment of root secondary metabolites across different TK levels.

Conclusions: Licorice specifically selects root-associated core bacteria over the course of plant development, and TK is correlated with root secondary metabolites and individual core-enriched taxa in the bulk and rhizosphere soils, which may have implications for practical licorice cultivation.
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http://dx.doi.org/10.1007/s11104-020-04692-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468178PMC
September 2020

Stochastic processes shape the biogeographic variations in core bacterial communities between aerial and belowground compartments of common bean.

Environ Microbiol 2021 02 21;23(2):949-964. Epub 2020 Sep 21.

State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Science, Northwest A&F University, Yangling, Shaanxi, 712100, China.

Although studies of biogeography in soil bacterial communities have attracted considerable attention, the generality of these patterns along with assembly processes and underlying drivers is poorly understood in the inner tissues of plants. Plant tissues provide unique ecological habitats for microorganisms, which play an essential role in plant performance. Here, we compared core bacterial communities among five soil-plant associated compartments of common bean across five sampling sites in China. Neutral and null modelling consistently suggested that stochastic processes dominated the core community assembly processes and escalated from the belowground compartments to the inner tissues of aerial plant parts. The multiple distance-decay relationships also varied and had flattened patterns in the stem endosphere, which were shaped by distinct environmental factors in each compartment. Coexistence patterns also varied in topological features, in addition with the sparsest networks in the stem endosphere resulted from the interaction with the stochastic processes. This study considerably expanded our understanding of various biogeographic patterns, assembly processes, and the underlying mechanisms of core bacterial communities between aerial and belowground compartments of common bean. That will provide a scientific basis for the reasonable regulation of core bacterial consortia to get better plant performance.
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http://dx.doi.org/10.1111/1462-2920.15227DOI Listing
February 2021

Fungi show broader environmental thresholds in wet than dry agricultural soils with distinct biogeographic patterns.

Sci Total Environ 2021 Jan 18;750:141761. Epub 2020 Aug 18.

State Key Laboratory of Crop Stress Biology in Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, PR China. Electronic address:

It is critical to establish response thresholds for fungal communities to global environmental change and assess the relationship between fungal diversity and nutrient cycling in soils. However, these have not yet been evaluated in agro-ecosystems. Here we report the findings of a survey across eastern China on the soil fungi and physicochemical properties in adjacent maize and rice fields. The results revealed a wider range of environmental thresholds for soil fungi in rice than maize fields. We found that the dominant fungal taxa only accounted for 0.6% of all taxa, but constituted >50% of total fungi. Based on their habitat preferences, distinct distribution maps between maize and rice fields were constructed, which indicated niche differentiation of soil fungi between dry and waterlogged soils. Rice fields showed higher fungal richness in low latitude regions, consistent with latitudinal richness patterns found in natural terrestrial ecosystems; however, no such trend was observed in maize fields. Fungal richness was positively correlated with nutrient cycling in rice soils and fungal beta diversity with nutrient cycling in maize soils. These findings provide response thresholds for fungal community change across environmental gradients, advancing our understanding of soil fungal diversity patterns in agricultural ecosystems. Differences between wetland and dryland should be taken into consideration when formulating sustainable management plans and baselines for assessments of future global change and resilience of agricultural fields.
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http://dx.doi.org/10.1016/j.scitotenv.2020.141761DOI Listing
January 2021

Identification of Robinia pseudoacacia target proteins responsive to Mesorhizobium amphore CCNWGS0123 effector protein NopT.

J Exp Bot 2020 12;71(22):7347-7363

State Key Laboratory of Crop Stress Biology in Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A & F University, Yangling, Shaanxi, China.

Nodulation outer proteins secreted via type 3 secretion systems are involved in the process of symbiosis between legume plants and rhizobia. To study the function of NopT in symbiosis, we mutated nopT in Mesorhizobium amphore CCNWGS0123 (GS0123), which can nodulate black locust (Robinia pseudoacacia). The nopT mutant induced higher levels of jasmonic acid, salicylic acid, and hydrogen peroxide accumulation in the roots of R. pseudoacacia compared with wild-type GS0123. The ΔnopT mutant induced higher disease-resistant gene expression 72 hours post-inoculation (hpi), whereas GS0123 induced higher disease-resistant gene expression earlier, at 36 hpi. Compared with the nopT mutant, GS0123 induced the up-regulation of most genes at 36 hpi and the down-regulation of most genes at 72 hpi. Proteolytically active NopT_GS0123 induced hypersensitive responses when expressed transiently in tobacco leaves (Nicotiana benthamiana). Two NopT_GS0123 targets in R. pseudoacacia were identified, ATP-citrate synthase alpha chain protein 2 and hypersensitive-induced response protein. Their interactions with NopT_GS0123 triggered resistance by the plant immune system. In conclusion, NopT_GS0123 inhibited the host plant immune system and had minimal effect on nodulation in R. pseudoacacia. Our results reveal the underlying molecular mechanism of NopT function in plant-symbiont interactions.
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http://dx.doi.org/10.1093/jxb/eraa405DOI Listing
December 2020

Abundant fungi adapt to broader environmental gradients than rare fungi in agricultural fields.

Authors:
Shuo Jiao Yahai Lu

Glob Chang Biol 2020 08 31;26(8):4506-4520. Epub 2020 May 31.

College of Urban and Environmental Sciences, Peking University, Beijing, P. R. China.

Soil communities are intricately linked to ecosystem functioning, and a predictive understanding of how communities assemble in response to environmental change is of great ecological importance. Little is known about the assembly processes governing abundant and rare fungal communities across agro-ecosystems, particularly with regard to their environmental adaptation. By considering abundant and rare taxa, we tested the environmental thresholds and phylogenetic signals for ecological preferences of fungal communities across complex environmental gradients to reflect their environmental adaptation, and explored the factors influencing their assembly based on the large-scale soil survey in agricultural fields across eastern China. We found that the abundant taxa exhibited remarkably broader response thresholds and stronger phylogenetic signals for the ecological preferences across environmental gradients compared to the rare taxa. Neutral processes played a key role in shaping the abundant subcommunity compared to the rare subcommunity. Null model analysis revealed that the abundant subcommunity was less clustered phylogenetically and governed primarily by dispersal limitation, while homogeneous selection was the major assembly process in the rare subcommunity. Soil available sulfur was the major factor mediating the balance between stochastic and deterministic processes of both the abundant and rare subcommunities, as indicated by an increase in stochasticity with higher available sulfur concentration. Based on macroecological spatial scale datasets, our study revealed the potential broader environmental adaptation of abundant fungal taxa compared to rare fungal taxa, and identified the factors mediating their distinct community assembly processes in agricultural fields. These results contribute to our understanding of the mechanisms underlying the generation and maintenance of fungal diversity in response to global environmental change.
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http://dx.doi.org/10.1111/gcb.15130DOI Listing
August 2020

Carbon nanomaterials affect carbon cycle-related functions of the soil microbial community and the coupling of nutrient cycles.

J Hazard Mater 2020 05 21;390:122144. Epub 2020 Jan 21.

Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China. Electronic address:

Many studies have examined changes in soil microbial community structure and composition by carbon nanomaterials (CNMs). Few, however, have investigated their impact on microbial community functions. This study explored how fullerene (C) and multi-walled carbon nanotubes (M50) altered functionality of an agricultural soil microbial community (Archaea, Bacteria and Eukarya), using microcosm experiments combined with GeoChip microarray. M50 had a stronger effect than C on alpha diversity of microbial functional genes; both CNMs increased beta diversity, resulting in functional profiles distinct from the control. M50 exerted a broader, severer impact on microbially mediated nutrient cycles. Together, these two CNMs affected CO fixation pathways, microbial degradation of diverse carbohydrates, secondary plant metabolites, lipids and phospholipids, proteins, as well as methanogenesis and methane oxidation. They also suppressed nitrogen fixation, nitrification, dissimilatory nitrogen reduction, eukaryotic assimilatory nitrogen reduction, and anaerobic ammonium oxidation (anammox). Phosphorus and sulfur cycles were less vulnerable; only phytic acid hydrolysis and sulfite reduction were inhibited by M50 but not C. Network analysis suggested decoupling of nutrient cycles by CNMs, manifesting closer and more hierarchical gene networks. This work reinforces profound impact of CNMs on soil microbial community functions and ecosystem services, laying a path for future investigation in this direction.
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http://dx.doi.org/10.1016/j.jhazmat.2020.122144DOI Listing
May 2020

Balance between community assembly processes mediates species coexistence in agricultural soil microbiomes across eastern China.

ISME J 2020 01 14;14(1):202-216. Epub 2019 Oct 14.

College of Urban and Environmental Sciences, Peking University, Beijing, PR China.

Revealing the linkages between community assembly and species coexistence, which is crucial for the understanding of ecosystem diversity and functioning, is a fundamental but rarely investigated subject in microbial ecology. Here we examined archaeal, bacterial, and fungal community assembly in adjacent pairs of maize (water-unsaturated) and rice (water-saturated) fields across different habitats and regions throughout Eastern China. The high-throughput sequencing dataset was analyzed by variation partitioning, null model, and neutral community model analyses. We demonstrated that microbial community assembly was governed more by species sorting than by dispersal limitation in maize fields, and to a lesser extent in rice fields. The relative importance of species sorting in maize soils was greater at low latitudes than at high latitudes, while rice soils exhibited an opposite trend. Microbial co-occurrence associations tended to be higher when communities were primarily driven by dispersal limitation relative to species sorting. There were greater community dissimilarities between maize and rice soils in low-latitude regions, which was consistent with the higher proportion of negative edges in the correlation networks. The results indicate that a balance between species sorting and dispersal limitation mediates species coexistence in soil microbiomes. This study enhances our understanding of contemporary coexistence theory in microbial ecosystems.
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http://dx.doi.org/10.1038/s41396-019-0522-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6908645PMC
January 2020

Soil pH and temperature regulate assembly processes of abundant and rare bacterial communities in agricultural ecosystems.

Authors:
Shuo Jiao Yahai Lu

Environ Microbiol 2020 03 18;22(3):1052-1065. Epub 2019 Oct 18.

College of Urban and Environmental Sciences, Peking University, Beijing, 100871, P. R. China.

The factors determining stochastic and deterministic processes that drive microbial community structure, specifically the balance of abundant and rare bacterial taxa, remain underexplored. Here we examined biogeographic patterns of abundant and rare bacterial taxa and explored environmental factors influencing their community assembly processes in agricultural fields across eastern China. More phylogenetic turnover correlating with spatial distance was observed in abundant than rare sub-communities. Homogeneous selection was the main assembly process for both the abundant and rare sub-communities; however, the abundant sub-community was more tightly clustered phylogenetically and was more sensitive to dispersal limitations than the rare sub-community. Rare sub-community of rice fields and abundant sub-community of maize fields were more governed by stochastic assembly processes, which showed higher operational taxonomic unit richness. We propose a conceptual paradigm wherein soil pH and mean annual temperature mediate the assembly of the abundant and rare sub-communities respectively. A higher soil pH leads to deterministic assembly of the abundant sub-community. For the rare sub-community, the dominance of stochasticity in low-temperature regions indicates weaker niche-based exclusion and the arrival of more evolutionary lineages. These findings suggest that the community assembly processes for abundant and rare bacterial taxa are dependent on distinct environmental variables in agro-ecosystems.
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http://dx.doi.org/10.1111/1462-2920.14815DOI Listing
March 2020

The Root Endophytic Fungi Community Structure of from Four Representative Provinces in China.

Microorganisms 2019 Sep 9;7(9). Epub 2019 Sep 9.

College of Life Sciences, Yan'an University, Yan'an 716000, China.

is a good forage grass with high biomass production and crude proteins. However, little is known about the endophytic fungi diversity of , which might play an important role in the plant's growth and biomass production. Here, we used high throughput sequencing of the Internal Transcribed Spacer (ITS) sequences based on primers ITS5-1737 and ITS2-2043R to investigate the endophytic fungi diversity of roots at the maturity stage, as collected from four provinces (Shaanxi province, SX; Fujian province, FJ; the Xinjiang Uyghur autonomous prefecture, XJ and Inner Mongolia, including sand (NS) and saline-alkali land (NY), China). The ITS sequences were processed using QIIME and R software. A total of 374,875 effective tags were obtained, and 708 operational taxonomic units (OTUs) were yielded with 97% identity in the five samples. Ascomycota and Basidiomycota were the two dominant phyla in the five samples, and the genera and were the most abundant in the FJ and XJ samples, respectively, while the most abundant tags in the other three samples could not be annotated at the genus level. In addition, our study revealed that the FJ sample possessed the highest OTU numbers (242) and the NS sample had the lowest (86). Moreover, only 22 OTUs were present in all samples simultaneously. The beta diversity analysis suggested a division of two endophytic fungi groups: the FJ sample from the south of China and the other four samples from north or northwest China. Correlation analysis between the environmental factors and endophytic fungi at the class level revealed that Sordariomycetes and Pucciniomycetes had extremely significant positive correlations with the total carbon, annual average precipitation, and annual average temperature, while Leotiomycetes showed an extremely significant negative correlation with quick acting potassium. The results revealed significant differences in the root endophytic fungi diversity of in different provinces and might be useful for growth promotion and biomass production in the future.
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http://dx.doi.org/10.3390/microorganisms7090332DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6780252PMC
September 2019

Dominant role of abundant rather than rare bacterial taxa in maintaining agro-soil microbiomes under environmental disturbances.

Chemosphere 2019 Nov 24;235:248-259. Epub 2019 Jun 24.

College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China. Electronic address:

Elucidating the mechanisms underpinning the responses of abundant and rare microbial taxa to environmental disturbances is essential for understanding the biodiversity-stability relationship and maintaining microbial diversity. Here, we explored the response patterns of abundant and rare bacterial taxa to disturbances by invasive plant growth and oil contamination in agricultural soils across a large spatial scale (latitude gradient = 18.62°-46.51°). Our meta-analysis based on existing Illumina sequencing datasets showed that abundant taxa persisted under the disturbances whereas rare taxa were more easily affected, indicating the higher resilience or resistance of abundant taxa to disturbances. The responses of abundant taxa were associated with mean annual temperature at the sampling sites, while rare taxa instead showed stochastic responses. There were significantly negative linear regressions between bacterial α-diversity and community dissimilarities (disturbed vs. undisturbed soils), suggesting stronger resilience or resistance in those bacterial communities with higher α-diversity. This resilience or resistance was mainly associated with the α-diversity of abundant taxa. Our network analysis showed that the disturbances substantially decreased the strength of the connections, loosened the co-occurrence relationships, and reshaped the complex bacterial interactions. In the undisturbed soils, abundant taxa were located in central positions within the network more often than were rare taxa, while these trends were reversed in the disturbed soils. Our results suggest that abundant taxa play a dominant role in the stability and maintenance of agro-soil bacterial communities, while rare taxa could greatly influence local bacterial interactions under environmental disturbances.
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http://dx.doi.org/10.1016/j.chemosphere.2019.06.174DOI Listing
November 2019

New Insight into the Evolution of Symbiotic Genes in Black Locust-Associated Rhizobia.

Genome Biol Evol 2019 07;11(7):1736-1750

State Key Laboratory of Crop Stress Biology in Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.

Nitrogen fixation in legumes occurs via symbiosis with rhizobia. This process involves packages of symbiotic genes on mobile genetic elements that are readily transferred within or between rhizobial species, furnishing the recipient with the ability to interact with plant hosts. However, it remains elusive whether plant host migration has played a role in shaping the current distribution of genetic variation in symbiotic genes. Herein, we examined the genetic structure and phylogeographic pattern of symbiotic genes in 286 symbiotic strains of Mesorhizobium nodulating black locust (Robinia pseudoacacia), a cross-continental invasive legume species that is native to North America. We conducted detailed phylogeographic analysis and approximate Bayesian computation to unravel the complex demographic history of five key symbiotic genes. The sequencing results indicate an origin of symbiotic genes in Germany rather than North America. Our findings provide strong evidence of prehistoric lineage splitting and spatial expansion events resulting in multiple radiations of descendent clones from founding sequence types worldwide. Estimates of the timescale of divergence in North American and Chinese subclades suggest that black locust-specific symbiotic genes have been present in these continent many thousands of years before recent migration of plant host. Although numerous crop plants, including legumes, have found their centers of origin as centers of evolution and diversity, the number of legume-specific symbiotic genes with a known geographic origin is limited. This work sheds light on the coevolution of legumes and rhizobia.
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http://dx.doi.org/10.1093/gbe/evz116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6698633PMC
July 2019

Author Correction: Bacterial and fungal gut communities of Agrilus mali at different developmental stages and fed different diets.

Sci Rep 2019 May 23;9(1):7987. Epub 2019 May 23.

Laboratory of Forestry Pests Biological Control, College of Forestry, Northwest A&F University, Yangling, Shaanxi, 712100, China.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
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http://dx.doi.org/10.1038/s41598-019-41873-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6531433PMC
May 2019

Core Microbiota in Agricultural Soils and Their Potential Associations with Nutrient Cycling.

mSystems 2019 Mar-Apr;4(2). Epub 2019 Mar 26.

College of Urban and Environmental Sciences, Peking University, Beijing, People's Republic of China.

Revealing the ecological roles of the core microbiota in community maintaining and soil nutrient cycling is crucial for understanding ecosystem function, yet there is a dearth of continental-scale studies on this fundamental topic in microbial ecology. Here, we collected 251 soil samples from adjacent pairs of maize and rice fields at a continental scale in eastern China. We revealed the major ecological roles of the core microbiota in maintaining complex connections between bacterial taxa and their associations with belowground multinutrient cycling. By identifying the habitat preferences of the core microbiota, we built a continental atlas for mapping the spatial distributions of bacteria in agro-soils, which helps forecast the responses of agricultural ecosystems to anthropogenic disturbance. The multinutrient cycling index for maize and rice soils was related to bacterial -diversity and -diversity, respectively. Rice soils exhibited higher bacterial diversity and closer bacterial cooccurrence relationships than maize soils. In contrast to the macro- or microecological latitudinal richness patterns in natural terrestrial ecosystems, the bacteria in maize soils showed higher richness at high latitudes; however, this trend was not observed in rice soils. This study provides a new perspective on the distinct bacterial biogeographic patterns to predict the ecological roles of the core microbiota in agro-soils and thus helps manage soil bacterial communities for better provisioning of key ecosystem services. Disentangling the roles of the core microbiota in community maintaining and soil nutrient cycling is an important yet poorly understood topic in microbial ecology. This study presents an exploratory effort to gain predictive understanding of the spatial atlas and ecological roles of the core microbiota. A systematic, continental-scale survey was conducted using agro-soils in adjacent pairs of maize (dryland) and rice (wetland) fields across eastern China. The results indicate that the core microbiota play major ecological roles in maintaining complex connections between bacterial taxa and are associated with belowground multinutrient cycling. A continental atlas was built for mapping the bacterial spatial distributions in agro-soils through identifying their habitat preferences. This study represents a significant advance in forecasting the responses of agricultural ecosystems to anthropogenic disturbance and thus helps manage soil bacterial communities for better provisioning of key ecosystem services-the ultimate goal of microbial ecology.
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http://dx.doi.org/10.1128/mSystems.00313-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435817PMC
March 2019

Environmental filtering drives distinct continental atlases of soil archaea between dryland and wetland agricultural ecosystems.

Microbiome 2019 02 1;7(1):15. Epub 2019 Feb 1.

College of Urban and Environmental Sciences, Peking University, Beijing, 100871, People's Republic of China.

Background: Understanding the spatial distributions and ecological diversity of soil archaeal communities in agricultural ecosystems is crucial for improvements in crop productivity. Here, we conducted a comprehensive, continental-scale survey of soil archaeal communities in adjacent pairs of maize (dryland) and rice (wetland) fields in eastern China.

Results: We revealed the consequential roles of environmental filtering in driving archaeal community assembly for both maize and rice fields. Rice fields, abundant with Euryarchaeota, had higher archaeal diversity and steeper distance-decay slopes than maize fields dominated by Thaumarchaeota. Dominant soil archaea showed distinct continental atlases and niche differentiation between dryland and wetland habitats, where they were associated with soil pH and mean annual temperature, respectively. After identifying their environmental preferences, we grouped the dominant archaeal taxa into different ecological clusters and determined the unique co-occurrence patterns within each cluster. Using this empirical dataset, we built a continental atlas of soil archaeal communities to provide reliable estimates of their spatial distributions in agricultural ecosystems.

Conclusions: Environmental filtering plays a crucial role in driving the distinct continental atlases of dominant soil archaeal communities between dryland and wetland, with contrasting strategies of archaeal-driven nutrient cycling within these two agricultural ecosystems. These findings improve our ability to predict how soil archaeal communities respond to environmental changes and to manage soil archaeal communities for provisioning of agricultural ecosystem services.
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http://dx.doi.org/10.1186/s40168-019-0630-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6359761PMC
February 2019

Resilience and Assemblage of Soil Microbiome in Response to Chemical Contamination Combined with Plant Growth.

Appl Environ Microbiol 2019 03 6;85(6). Epub 2019 Mar 6.

State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, People's Republic of China

A lack of knowledge of the microbial responses to environmental change at the species and functional levels hinders our ability to understand the intrinsic mechanisms underlying the maintenance of microbial ecosystems. Here, we present results from temporal microcosms that introduced inorganic and organic contaminants into agro-soils for 90 days, with three common legume plants. Temporal dynamics and assemblage of soil microbial communities and functions in response to contamination under the influence of growth of different plants were explored via sequencing of the 16S rRNA amplicon and by shotgun metagenomics. Soil microbial alpha diversity and structure at the taxonomic and functional levels exhibited resilience patterns. Functional profiles showed greater resilience than did taxonomic ones. Different legume plants imposed stronger selection on taxonomic profiles than on functional ones. Network and random forest analyses revealed that the functional potential of soil microbial communities was fostered by various taxonomic groups. were important predictors of key functional traits such as amino acid metabolism, nucleic acid metabolism, and hydrocarbon degradation. Our study reveals the strong resilience of the soil microbiome to chemical contamination and sensitive responses of taxonomic rather than functional profiles to selection processes induced by different legume plants. This is pivotal to develop approaches and policies for the protection of soil microbial diversity and functions in agro-ecosystems with different response strategies from global environmental drivers, such as soil contamination and plant invasion. Exploring the microbial responses to environmental disturbances is a central issue in microbial ecology. Understanding the dynamic responses of soil microbial communities to chemical contamination and the microbe-soil-plant interactions is essential for forecasting the long-term changes in soil ecosystems. Nevertheless, few studies have applied multi-omics approaches to assess the microbial responses to soil contamination and the microbe-soil-plant interactions at the taxonomic and functional levels simultaneously. Our study reveals clear succession and resilience patterns of soil microbial diversity and structure in response to chemical contamination. Different legume plants exerted stronger selection processes on taxonomic than on functional profiles in contaminated soils, which could benefit plant growth and fitness as well as foster the potential abilities of hydrocarbon degradation and metal tolerance. These results provide new insight into the resilience and assemblage of soil microbiome in response to environmental disturbances in agro-ecosystems at the species and functional levels.
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http://dx.doi.org/10.1128/AEM.02523-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6414375PMC
March 2019

Bacterial and fungal gut communities of Agrilus mali at different developmental stages and fed different diets.

Sci Rep 2018 10 23;8(1):15634. Epub 2018 Oct 23.

Laboratory of Forestry Pests Biological Control, College of Forestry, Northwest A&F University, Yangling, Shaanxi, 712100, China.

Agrilus mali (Coleoptera: Buprestidae) is an invasive wood borer pest that has caused considerable damage to the Xinjiang wild fruit forest. In this study, we investigated the bacterial and fungal intestinal microbial communities of A. mali during different developmental stages, including larvae, pupae and newly eclosed adults or fed different diets (leaves of Malus halliana and Malus pumila) using Illumina MiSeq high-throughput sequencing technology. The results showed that microbial alpha diversity first increased and then decreased during the developmental stages, with the most dominant bacteria and fungi exhibiting the dynamic patterns "Decrease", "Increase" and "Fluctuation". With respect to the different diets, the bacterial communities were similar between the newly eclosed adults and adults fed M. pumila leaves, while the structure of the fungal communities showed great differences between newly eclosed adults and adults fed different diets. Through a co-correlation network analysis, we observed complex microbial interactions among bacterial and fungal taxa that were associated with potential diverse functions and intricate biological processes in the intestinal microbiota of A. mali. Overall, the results of this study demonstrated that the invasive insect A. mali harbours diverse, dynamic, and presumably multifunctional microbial communities, an understanding of which could improve our ability to develop more effective management approaches to control A. mali.
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http://dx.doi.org/10.1038/s41598-018-34127-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6199299PMC
October 2018

Geographical pattern of methanogenesis in paddy and wetland soils across eastern China.

Sci Total Environ 2019 Feb 13;651(Pt 1):281-290. Epub 2018 Sep 13.

College of Urban and Environmental Sciences, Peking University, Beijing, China. Electronic address:

Large variation of CH emissions from paddy and wetland ecosystems exists across different geographical locations in China. To obtain mechanistic understanding of this variation, we investigated the dynamics of methanogenesis over the course of glucose degradation in fourteen paddy field soils and five wetland soils collected from different regions of China. The results revealed that the maximal rate (2-3 mM per day) and the total amount (25-30 mM) of CH produced were similar across soil samples. The lag phase of methanogenesis, however, differed substantially with the shortest lag phase of 4 days in a paddy soil from north China and the longest of 32 days in a soil from south China, and this difference reflected a general geographical trend among all soils tested. Nitrate was reduced completely within 4 days in all soils. The reduction of Fe(III) and sulfate was completed after 21 days and 29 days, respectively. The depletion time of Fe(III) and sulfate were positively correlated with the lag phase of methanogenesis. Competition for common substrates between methanogens and iron and sulfate reducers, however, does not explain this coincidence because a slow production of CH was detected at the very beginning. It appears that the geographical variations in methanogenesis and the reduction of ferric iron and sulfate are related to the variation in soil pH but not to temperature, soil organic C and nutrient conditions in paddy and wetland soils across eastern China.
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http://dx.doi.org/10.1016/j.scitotenv.2018.09.167DOI Listing
February 2019

Soil microbiomes with distinct assemblies through vertical soil profiles drive the cycling of multiple nutrients in reforested ecosystems.

Microbiome 2018 08 21;6(1):146. Epub 2018 Aug 21.

State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.

Background: Soil microbiomes play an important role in the services and functioning of terrestrial ecosystems. However, little is known of their vertical responses to restoration process and their contributions to soil nutrient cycling in the subsurface profiles. Here, we investigated the community assembly of soil bacteria, archaea, and fungi along vertical (i.e., soil depths of 0-300 cm) and horizontal (i.e., distance from trees of 30-90 cm) profiles in a chronosequence of reforestation sites that represent over 30 years of restoration.

Results: In the superficial layers (0-80 cm), bacterial and fungal diversity decreased, whereas archaeal diversity increased with increasing soil depth. As reforestation proceeded over time, the vertical spatial variation in bacterial communities decreased, while that in archaeal and fungal communities increased. Vertical distributions of the soil microbiomes were more related to the variation in soil properties, while their horizontal distributions may be driven by a gradient effect of roots extending from the tree. Bacterial and archaeal beta-diversity were strongly related to multi-nutrient cycling in the soil, respectively, playing major roles in deep and superficial layers.

Conclusions: Taken together, these results reveal a new perspective on the vertical and horizontal spatial variation in soil microbiomes at the fine scale of single trees. Distinct response patterns underpinned the contributions of soil bacteria, archaea, and fungi as a function of subsurface nutrient cycling during the reforestation of ex-arable land.
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http://dx.doi.org/10.1186/s40168-018-0526-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6104017PMC
August 2018

Novel Common Genetic Susceptibility Loci for Colorectal Cancer.

J Natl Cancer Inst 2019 02;111(2):146-157

Division of Research, Kaiser Permanente Medical Care Program of Northern California, Oakland, CA.

Background: Previous genome-wide association studies (GWAS) have identified 42 loci (P < 5 × 10-8) associated with risk of colorectal cancer (CRC). Expanded consortium efforts facilitating the discovery of additional susceptibility loci may capture unexplained familial risk.

Methods: We conducted a GWAS in European descent CRC cases and control subjects using a discovery-replication design, followed by examination of novel findings in a multiethnic sample (cumulative n = 163 315). In the discovery stage (36 948 case subjects/30 864 control subjects), we identified genetic variants with a minor allele frequency of 1% or greater associated with risk of CRC using logistic regression followed by a fixed-effects inverse variance weighted meta-analysis. All novel independent variants reaching genome-wide statistical significance (two-sided P < 5 × 10-8) were tested for replication in separate European ancestry samples (12 952 case subjects/48 383 control subjects). Next, we examined the generalizability of discovered variants in East Asians, African Americans, and Hispanics (12 085 case subjects/22 083 control subjects). Finally, we examined the contributions of novel risk variants to familial relative risk and examined the prediction capabilities of a polygenic risk score. All statistical tests were two-sided.

Results: The discovery GWAS identified 11 variants associated with CRC at P < 5 × 10-8, of which nine (at 4q22.2/5p15.33/5p13.1/6p21.31/6p12.1/10q11.23/12q24.21/16q24.1/20q13.13) independently replicated at a P value of less than .05. Multiethnic follow-up supported the generalizability of discovery findings. These results demonstrated a 14.7% increase in familial relative risk explained by common risk alleles from 10.3% (95% confidence interval [CI] = 7.9% to 13.7%; known variants) to 11.9% (95% CI = 9.2% to 15.5%; known and novel variants). A polygenic risk score identified 4.3% of the population at an odds ratio for developing CRC of at least 2.0.

Conclusions: This study provides insight into the architecture of common genetic variation contributing to CRC etiology and improves risk prediction for individualized screening.
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http://dx.doi.org/10.1093/jnci/djy099DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6555904PMC
February 2019

Biogeographic distribution of bacterial, archaeal and methanogenic communities and their associations with methanogenic capacity in Chinese wetlands.

Sci Total Environ 2018 May 13;622-623:664-675. Epub 2017 Dec 13.

College of Urban and Environmental Sciences, Peking University, Beijing 100871, China. Electronic address:

Natural wetlands and anthropogenic paddy fields are the dominant biogenic sources of atmospheric methane emission which have been speculated as the most probable sources for the increase of post-2006 atmospheric methane. Regional differences in CH emission is possibly due to microbial biogeographic distribution. Here we collected soils from 19 wetlands from different regions in China. The methane production capacity (MPC) was measured for each soil samples and varied from 1.11 to 841.94mg/kg dry soil. High throughput sequencing was employed to investigate the diversity and composition of bacterial, archaeal and methanogenic communities. Similar biogeographic patterns for bacterial, archaeal and methanogenic communities along the latitudinal gradient were observed, and the biogeographic assemblies of different microbial groups were driven by concurrent factors, including edaphic variables (total organic carbon, total phosphorus and pH) and climatic variables (annual frost days, mean annual temperature, direct solar radiation and mean annual precipitation). MPC was significantly correlated with TOC concentration, and in addition, various functional taxa were positively correlated with MPC (P<0.05), for example, Sphingomonas, Syntrophomonas, Methanospirillum and Methanoregula, indicating their potential contributions in the methanogenic process, and many of them were fermentative bacteria and methanogens. Network analysis showed that some syntrophs, sulfate-reducers and methanogens were tightly co-occurred in one module, suggesting their involvements in cross-linked functional processes. Our study implicated both temperature and substrate availability altered the biogeographic patterns of microbial community as well as methane production potential in Chinese wetlands.
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http://dx.doi.org/10.1016/j.scitotenv.2017.11.279DOI Listing
May 2018

Transcriptome Response to Heavy Metals in Sinorhizobium meliloti CCNWSX0020 Reveals New Metal Resistance Determinants That Also Promote Bioremediation by Medicago lupulina in Metal-Contaminated Soil.

Appl Environ Microbiol 2017 10 29;83(20). Epub 2017 Sep 29.

State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China

The symbiosis of the highly metal-resistant CCNWSX0020 and has been considered an efficient tool for bioremediation of heavy metal-polluted soils. However, the metal resistance mechanisms of CCNWSX00200 have not been elucidated in detail. Here we employed a comparative transcriptome approach to analyze the defense mechanisms of CCNWSX00200 against Cu or Zn exposure. Six highly upregulated transcripts involved in Cu and Zn resistance were identified through deletion mutagenesis, including genes encoding a multicopper oxidase (CueO), an outer membrane protein (Omp), sulfite oxidoreductases (YedYZ), and three hypothetical proteins (a CusA-like protein, a FixH-like protein, and an unknown protein), and the corresponding mutant strains showed various degrees of sensitivity to multiple metals. The Cu-sensitive mutant (Δ) and three mutants that were both Cu and Zn sensitive (Δ, Δ-like, and Δ-like) were selected for further study of the effects of these metal resistance determinants on bioremediation. The results showed that inoculation with the Δ mutant severely inhibited infection establishment and nodulation of under Cu stress, while inoculation with the Δ and Δ-like mutants decreased just the early infection frequency and nodulation under Cu and Zn stresses. In contrast, inoculation with the Δ-like mutant almost led to loss of the symbiotic capacity of to even grow in uncontaminated soil. Moreover, the antioxidant enzyme activity and metal accumulation in roots of inoculated with all mutants were lower than those with the wild-type strain. These results suggest that heavy metal resistance determinants may promote bioremediation by directly or indirectly influencing formation of the rhizobium-legume symbiosis. Rhizobium-legume symbiosis has been promoted as an appropriate tool for bioremediation of heavy metal-contaminated soils. Considering the plant-growth-promoting traits and survival advantage of metal-resistant rhizobia in contaminated environments, more heavy metal-resistant rhizobia and genetically manipulated strains were investigated. In view of the genetic diversity of metal resistance determinants in rhizobia, their effects on phytoremediation by the rhizobium-legume symbiosis must be different and depend on their specific assigned functions. Our work provides a better understanding of the mechanism of heavy metal resistance determinants involved in the rhizobium-legume symbiosis, and in further studies, genetically modified rhizobia harboring effective heavy metal resistance determinants may be engineered for the practical application of rhizobium-legume symbiosis for bioremediation in metal-contaminated soils.
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http://dx.doi.org/10.1128/AEM.01244-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5626999PMC
October 2017

Biogeography and ecological diversity patterns of rare and abundant bacteria in oil-contaminated soils.

Mol Ecol 2017 Oct 5;26(19):5305-5317. Epub 2017 Sep 5.

State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi, China.

Revealing the biogeographies and ecologies of rare and abundant microorganisms is crucial to understand ecosystem diversity and function. In this study, we investigated the biogeographic assemblies and ecological diversity patterns of rare and abundant bacteria in long-term oil-contaminated soils at intervals of 46-360 km by performing high-throughput sequencing of 16S rRNA genes. The results clearly revealed distinct distribution patterns for rare and abundant bacteria in soil samples. Rare taxa were unevenly distributed; however, abundant taxa were ubiquitous across all samples. Both rare and abundant subcommunities showed significant distance-decay relationships, and their assemblies were driven by different factors. The rare subcommunity primarily exhibited a spatially structured distribution (i.e., stochastic processes), while edaphic factors (i.e., deterministic processes) largely contributed to the structure of the abundant subcommunity. A network analysis revealed closer relationships between abundant bacteria and their heightened influence on other co-occurrences in the community compared with rare species. In conclusion, rare microbial taxa may play potential roles in maintaining ecosystem diversity, although they do not appear to be central to microbial networks. Abundant microbes are vital for microbial co-occurrences in oil-contaminated soils, and high relative abundance and ubiquitous distribution suggest potential roles in the degradation of organic pollutants.
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http://dx.doi.org/10.1111/mec.14218DOI Listing
October 2017

Ecological diversity and co-occurrence patterns of bacterial community through soil profile in response to long-term switchgrass cultivation.

Sci Rep 2017 06 15;7(1):3608. Epub 2017 Jun 15.

College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, 712100, P.R. China.

Switchgrass (Panicum virgatum L.) is a cellulosic biofuel feedstock and their effects on bacterial communities in deep soils remain poorly understood. To reveal the responses of bacterial communities to long-term switchgrass cultivation through the soil profile, we examined the shift of soil microbial communities with depth profiles of 0-60 cm in five-year switchgrass cultivation and fallow plots. The Illumina sequencing of the 16S rRNA gene showed that switchgrass cultivation significantly increased microbial OTU richness, rather than microbial Shannon diversity; however, there was no significant difference in the structure of microbial communities between switchgrass cultivation and fallow soils. Both switchgrass cultivation and fallow soils exhibited significant negative vertical spatial decay of microbial similarity, indicating that more vertical depth distant soils had more dissimilar communities. Specifically, switchgrass cultivation soils showed more beta-diversity variations across soil depth profile. Through network analysis, more connections and closer relationships of microbial taxa were observed in soils under switchgrass cultivation, suggesting that microbial co-occurrence patterns were substantially influenced by switchgrass cultivation. Overall, our study suggested that five-year switchgrass cultivation could generated more beta-diversity variations across soil depth and more complex inter-relationships of microbial taxa, although did not significantly shape the structure of soil microbial community.
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http://dx.doi.org/10.1038/s41598-017-03778-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5472595PMC
June 2017

Distinct succession patterns of abundant and rare bacteria in temporal microcosms with pollutants.

Environ Pollut 2017 Jun 21;225:497-505. Epub 2017 Mar 21.

State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, PR China. Electronic address:

Elucidating the driving forces behind the temporal dynamics of abundant and rare microbes is essential for understanding the assembly and succession of microbial communities. Here, we explored the successional trajectories and mechanisms of abundant and rare bacteria via soil-enrichment subcultures in response to various pollutants (phenanthrene, n-octadecane, and CdCl) using time-series Illumina sequencing datasets. The results reveal different successional patterns of abundant and rare sub-communities in eighty pollutant-degrading consortia and two original soil samples. A temporal decrease in α-diversity and high turnover rate for β-diversity indicate that deterministic processes are the main drivers of the succession of the abundant sub-community; however, the high cumulative species richness indicates that stochastic processes drive the succession of the rare sub-community. A functional prediction showed that abundant bacteria contribute primary functions to the pollutant-degrading consortia, such as amino acid metabolism, cellular responses to stress, and hydrocarbon degradation. Meanwhile, rare bacteria contribute a substantial fraction of auxiliary functions, such as carbohydrate-active enzymes, fermentation, and homoacetogenesis, which indicates their roles as a source of functional diversity. Our study suggests that the temporal succession of microbes in polluted microcosms is mainly associated with abundant bacteria rather than the high proportion of rare taxa. The major forces (i.e., stochastic or deterministic processes) driving microbial succession could be dependent on the low- or high-abundance community members in temporal microcosms with pollutants.
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http://dx.doi.org/10.1016/j.envpol.2017.03.015DOI Listing
June 2017
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