Publications by authors named "Andrew McMinn"

43 Publications

Effect of East Asian atmospheric particulate matter deposition on bacterial activity and community structure in the oligotrophic Northwest Pacific.

Environ Pollut 2021 Apr 5;283:117088. Epub 2021 Apr 5.

College of Marine Life Sciences, Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, 266003, China; Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003, China.

Large amounts of anthropogenic East Asian (EA) particulate matters (PM), containing inorganic nutrients and organic matter, are deposited in the oligotrophic Northwest Pacific Ocean. However, the effects of such deposition on marine microbes remain unclear. In this study, the effect of EA PM deposition on marine bacteria was assessed by five on-board microcosm experiments, conducted in oligotrophic basins of the South China Sea. The addition of EA PM to the sampling water induced a clear shift in bacterial community composition from prevailing oligotrophs (i.e., SAR 11 clade, Prochlorococcus, AEGEAN-169 marine group) to less common copiotrophs (i.e., Alteromonas, Ruegeria, Flavobacteriaceae) and thus a slight increase in bacterial diversity. The shift to more active community composition, as well as stimulation of PM nutrients, resulted in a large increase in cell-specific and bulk bacterial production. In contrast, there were only minor changes in bacterial abundance, possibly due to increased top-down mortality. The EA PM also exhibited a stronge toxic effect on pico-cyanobacteria, leading to a significant decrease in their proportion. Moreover, the responses of bacterial metabolism and community composition exhibited significant relationships with the hydrographic condition of the locations. Stronger promotion effects of the EA PM on bacterial production and community shift from oligotrophs to copiotrophs was demonstrated at the more oligotrophic sites with lower chlorophyll a concentrations. These results suggest that PM deposition from polluted areas has the potential to alter the typical oligotrophic microbiomes and change the net metabolic balance of the bacterial community. These will then influence the dynamics of carbon flow in microbial food webs and biogeochemical cycles, especially with the trend of global warming and expansion of low-chlorophyll regions.
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http://dx.doi.org/10.1016/j.envpol.2021.117088DOI Listing
April 2021

Comparison of Deep-Sea Picoeukaryotic Composition Estimated from the V4 and V9 Regions of 18S rRNA Gene with a Focus on the Hadal Zone of the Mariana Trench.

Microb Ecol 2021 Apr 3. Epub 2021 Apr 3.

College of Marine Life Sciences, Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, China.

Diversity of microbial eukaryotes is estimated largely based on sequencing analysis of the hypervariable regions of 18S rRNA genes. But the use of different regions of 18S rRNA genes as molecular markers may generate bias in diversity estimation. Here, we compared the differences between the two most widely used markers, V4 and V9 regions of the 18S rRNA gene, in describing the diversity of epipelagic, bathypelagic, and hadal picoeukaryotes in the Challenger Deep of the Mariana Trench, which is a unique and little explored environment. Generally, the V9 region identified more OTUs in deeper waters than V4, while the V4 region provided greater Shannon diversity than V9. In the epipelagic zone, where Alveolata was the dominant group, picoeukaryotic community compositions identified by V4 and V9 markers are similar at different taxonomic levels. However, in the deep waters, the results of the two datasets show clear differences. These differences were mainly contributed by Retaria, Fungi, and Bicosoecida. The primer targeting the V9 region has an advantage in amplifying Bicosoecids in the bathypelagic and hadal zone of the Mariana Trench, and its high abundance in V9 dataset pointed out the possibility of Bicosoecids as a dominant group in this environment. Chrysophyceae, Fungi, MALV-I, and Retaria were identified as the dominant picoeukaryotes in the bathypelagic and hadal zone and potentially play important roles in deep-sea microbial food webs and biogeochemical cycling by their phagotrophic, saprotrophic, and parasitic life styles. Overall, the use of different markers of 18S rRNA gene allows a better assessment and understanding of the picoeukaryotic diversity in deep-sea environments.
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http://dx.doi.org/10.1007/s00248-021-01747-2DOI Listing
April 2021

Mechanistic insights into substrate recognition and catalysis of a new ulvan lyase of the polysaccharide lyase family 24.

Appl Environ Microbiol 2021 Mar 26. Epub 2021 Mar 26.

State Key Laboratory of Microbial Technology, Shandong University, Qingdao, 266237, China

Ulvan is an important marine polysaccharide. Bacterial ulvan lyases play important roles in ulvan degradation and marine carbon cycling. Until now, only a small number of ulvan lyases have been characterized. Here, a new ulvan lyase, Uly1, belonging to the polysaccharide lyase (PL) family 24 from the marine bacterium is characterized. The optimal temperature and pH for Uly1 to degrade ulvan are 40°C and pH 9.0, respectively. Uly1 degrades ulvan polysaccharides in the endolytic manner, mainly producing ΔRha3S, consisting of an unsaturated 4-deoxy-L--hex-4-enopyranosiduronic acid and a 3-O-sulfated α-L-rhamnose. The structure of Uly1 was resolved at a 2.10 Å resolution. Uly1 adopts a seven-bladed β-propeller architecture. Structural and site-directed mutagenesis analyses indicate that four highly conserved residues, H128, H149, Y223 and R239, are essential for catalysis. H128 functions as both the catalytic acid and base, H149 and R239 function as the neutralizers, and Y223 plays a supporting role in catalysis. Structural comparison and sequence alignment suggest that Uly1 and many other PL24 enzymes may directly bind the substrate near the catalytic residues for catalysis, different from the PL24 ulvan lyase LOR_107 adopting a two-stage substrate binding process. This study provides new insights into ulvan lyases and ulvan degradation.Ulvan is a major cell wall component of green algae of the genus Many marine heterotrophic bacteria can produce extracellular ulvan lyases to degrade ulvan for carbon nutrient. In addition, ulvan has a range of physiological bioactivities based on its specific chemical structure. Ulvan lyase thus plays an important role in marine carbon cycling and has great potential in biotechnological applications. However, only a small number of ulvan lyases have been characterized over the past ten years. Here, based on biochemical and structural analyses, a new ulvan lyase of polysaccharide lyase family 24 is characterized and its substrate recognition and catalytic mechanisms are revealed. Moreover, a new substrate binding process adopted by PL24 ulvan lyases is proposed. This study offers a better understanding of bacterial ulvan lyases and is helpful for studying the application potentials of ulvan lyases.
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http://dx.doi.org/10.1128/AEM.00412-21DOI Listing
March 2021

Characterization and genome analysis of phage AL infecting Pseudoalteromonas marina.

Virus Res 2021 Apr 4;295:198265. Epub 2021 Feb 4.

College of Marine Life Sciences and Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, China; Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia.

Although Pseudoalteromonas is an abundant, ubiquitous, marine algae-associated bacterial genus, there is still little information on their phages. In the present study, a marine phage AL, infecting Pseudoalteromonas marina, was isolated from the coastal waters off Qingdao. The AL phage is a siphovirus with an icosahedral head of 53 ± 1 nm and a non-contractile tail, length of 99 ± 1 nm. A one-step growth curve showed that the latent period was approximately 70 min, the rise period was 50 min, and the burst size was 227 pfu/cell. The genome sequence of this phage is a 33,582 bp double-stranded DNA molecule with a GC content of 40.1 %, encoding 52 open reading frames (ORFs). The order of the functional genes, especially those related to the structure module, is highly conserved and basically follows the common pattern used by siphovirus. The stable order has been formed during the long-term evolution of phages in the siphovirus group, which has helped the phages to maintain their normal morphology and function. Phylogenetic trees based on the major capsid protein (mcp) and genome-wide sequence have shown that the AL phage is closely related to four Pseudoalteromonas phages, including PHS21, PHS3, SL25 and Pq0. Further analysis using all-to-all BLASTP also confirmed that this phage shared high sequence homology with the same four Pseudoalteromonas phages, with amino acid sequence identities ranging from 44 % to 71 %. In particular, their similarity in virion structure module may imply that these phages share common assembly mechanism characteristics and infection pathways. Pseudoalteromonas phage AL not only provides basic information for the further study of the evolution of Pseudoalteromonas phages and interactions between marine phage and host but also helps to explain the unknown viral sequences in the metagenomic databases.
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http://dx.doi.org/10.1016/j.virusres.2020.198265DOI Listing
April 2021

Rapid Manipulation in Irradiance Induces Oxidative Free-Radical Release in a Fast-Ice Algal Community (McMurdo Sound, Antarctica).

Front Plant Sci 2020 25;11:588005. Epub 2020 Nov 25.

School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand.

Sea ice supports a unique assemblage of microorganisms that underpin Antarctic coastal food-webs, but reduced ice thickness coupled with increased snow cover will modify energy flow and could lead to photodamage in ice-associated microalgae. In this study, microsensors were used to examine the influence of rapid shifts in irradiance on extracellular oxidative free radicals produced by sea-ice algae. Bottom-ice algal communities were exposed to one of three levels of incident light for 10 days: low (0.5 μmol photons m s, 30 cm snow cover), mid-range (5 μmol photons m s, 10 cm snow), or high light (13 μmol photons m s, no snow). After 10 days, the snow cover was reversed (either removed or added), resulting in a rapid change in irradiance at the ice-water interface. In treatments acclimated to low light, the subsequent exposure to high irradiance resulted in a ~400× increase in the production of hydrogen peroxide (HO) and a 10× increase in nitric oxide (NO) concentration after 24 h. The observed increase in oxidative free radicals also resulted in significant changes in photosynthetic electron flow, RNA-oxidative damage, and community structural dynamics. In contrast, there was no significant response in sea-ice algae acclimated to high light and then exposed to a significantly lower irradiance at either 24 or 72 h. Our results demonstrate that microsensors can be used to track real-time stress in sea-ice microbial communities. Extrapolating to ecologically relevant spatiotemporal scales remains a significant challenge, but this approach offers a fundamentally enhanced level of resolution for quantifying the microbial response to global change.
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http://dx.doi.org/10.3389/fpls.2020.588005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7723870PMC
November 2020

Experimental evidence for long-term coexistence of copiotrophic and oligotrophic bacteria in pelagic surface seawater.

Environ Microbiol 2021 02 21;23(2):1162-1173. Epub 2020 Nov 21.

College of Marine Life Sciences, Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, 266003, China.

Most marine copiotrophic bacteria can produce extracellular enzymes to degrade biopolymers into bio-available smaller solutes, while oligotrophic bacteria usually cannot. Bacterial extracellular enzymes and enzymatic products can be a common resource that could be utilized by both copiotrophs and oligotrophs; when present, oligotrophs may outcompete the enzyme-producing copiotrophs. However, copiotrophs and oligotrophs consistently coexist in the ocean. How they maintain coexistence has still not been experimentally studied. In this study, the interaction and coexistence of a copiotroph and an oligotroph, isolated from the same surface seawater sample and utilizing the same proteinaceous substrate, were experimentally investigated. The copiotroph could secrete extracellular proteases to degrade and then utilize the proteinaceous substrate. The oligotroph was unable to utilize the proteinaceous substrate by itself, but could grow by using the hydrolysate amino acids. The copiotroph outcompeted the oligotroph by adsorbing the amino acids quickly and having a higher growth rate in the rich medium. The oligotroph survived by adapting to low concentration of nutrients. The copiotroph and oligotroph were able to maintain long-term (up to 142 days) coexistence in the laboratory. This study indicates that differences in the utilization of different concentrations of nutrients can drive the coexistence of marine copiotrophs and oligotrophs.
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http://dx.doi.org/10.1111/1462-2920.15321DOI Listing
February 2021

Genomic analysis of Synechococcus phage S-B43 and its adaption to the coastal environment.

Virus Res 2020 11 14;289:198155. Epub 2020 Sep 14.

College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China; Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China; Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7001, Australia.

Synechococcus dominate picocyanobacterial communities in coastal environments. However, only a few Synechococcus phages have been described from the coastal seas of the Northwest Pacific Ocean. Here a new Synechococcus phage, S-B43 was isolated from the Bohai Sea, a semi-closed coastal sea of the Northwest Pacific Ocean. S-B43 is a member of Myoviridae, containing 275 predicted open reading frames. Fourteen auxiliary metabolic genes (AMG) were identified from the genome of S-B43, including five photosynthetic associated genes and several AMGs related to its adaption to the high turbidity and eutrophic coastal environment with a low ratio of phosphorus to nitrogen (HNLP). The occurrences of 31 AMGs among 34 cyanophage genomes indicates that AMGs zwf, gnd, speD, petF and those coding for FECH and thioredoxin were more common in coastal areas than in the open ocean and AMGs pebS and ho1 were more prevalent in the open ocean. The occurrence of cyanophage AMGs in different environments might be a reflection of the environmental adaption of their hosts. This study contributes to our understanding of the interactions between cyanobacteria and cyanophages and their environmental adaption to the coastal environment.
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http://dx.doi.org/10.1016/j.virusres.2020.198155DOI Listing
November 2020

Genome Analysis of Two Novel Phages That Lack Common Auxiliary Metabolic Genes: Possible Reasons and Ecological Insights by Comparative Analysis of Cyanomyoviruses.

Viruses 2020 07 25;12(8). Epub 2020 Jul 25.

College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.

The abundant and widespread unicellular cyanobacteria plays an important role in contributing to global phytoplankton primary production. In the present study, two novel cyanomyoviruses, S-N03 and S-H34 that infected MW02, were isolated from the coastal waters of the Yellow Sea. S-N03 contained a 167,069-bp genome comprising double-stranded DNA with a G + C content of 50.1%, 247 potential open reading frames and 1 tRNA; S-H34 contained a 167,040-bp genome with a G + C content of 50.1%, 246 potential open reading frames and 5 tRNAs. These two cyanophages contain fewer auxiliary metabolic genes (AMGs) than other previously isolated cyanophages. S-H34 in particular, is currently the only known cyanomyovirus that does not contain any AMGs related to photosynthesis. The absence of such common AMGs in S-N03 and S-H34, their distinct evolutionary history and ecological features imply that the energy for phage production might be obtained from other sources rather than being strictly dependent on the maintenance of photochemical ATP under high light. Phylogenetic analysis showed that the two isolated cyanophages clustered together and had a close relationship with two other cyanophages of low AMG content. Comparative genomic analysis, habitats and hosts across 81 representative cyanomyovirus showed that cyanomyovirus with less AMGs content all belonged to phages isolated from eutrophic waters. The relatively small genome size and high G + C content may also relate to the lower AMG content, as suggested by the significant correlation between the number of AMGs and G + C%. Therefore, the lower content of AMG in S-N03 and S-H34 might be a result of viral evolution that was likely shaped by habitat, host, and their genomic context. The genomic content of AMGs in cyanophages may have adaptive significance and provide clues to their evolution.
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http://dx.doi.org/10.3390/v12080800DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7472177PMC
July 2020

Editorial: Thematic issue on polar and alpine microbiology.

FEMS Microbiol Ecol 2020 08;96(8)

Department of Biochemistry and Microbiology, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901, USA.

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http://dx.doi.org/10.1093/femsec/fiaa136DOI Listing
August 2020

Characterization and Genome Analysis of a Novel Marine Alteromonas Phage P24.

Curr Microbiol 2020 Oct 25;77(10):2813-2820. Epub 2020 Jun 25.

College of Marine Life Sciences, Ocean University of China, No. 5 Yushan Road, Shinan District, Qingdao, 266071, People's Republic of China.

Although Alteromonas is ubiquitous in the marine environment, very little is known about Alteromonas phages, with only ten, thus far, being isolated and reported on. In this study, a novel double-stranded DNA phage, Alteromonas phage P24, which infects Alteromonas macleodii, was isolated from the coastal waters off Qingdao. Alteromonas phage P24 has a siphoviral morphology, with an icosahedral head, 61 ± 1 nm in diameter, and a tail length of 105 ± 1 nm. Alteromonas phage P24 contains lipids. It has an optimal temperature and pH for growth of 20℃ and 5-7, respectively. A one-step growth curve shows a latent period of 55 min, a rise period of 65 min, and an average burst size of approximately 147 virions per cell. Alteromonas phage P24 has the genome of 46,945 bp with 43.80% GC content and 74 open reading frames (ORFs) without tRNA. The results of the phylogenetic tree, based on the mcp and terL genes, show that Alteromonas phage P24 is closely related to Aeromonas phage phiARM81ld. Meanwhile, phylogenetic analysis based on the whole genome of P24 indicates that it forms a unique viral sub-cluster within Siphoviridae. This study contributes to the understanding of the genomic characteristics and the virus-host interactions of Alteromonas phages.
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http://dx.doi.org/10.1007/s00284-020-02077-1DOI Listing
October 2020

Effects of ocean acidification on Antarctic marine organisms: A meta-analysis.

Ecol Evol 2020 May 16;10(10):4495-4514. Epub 2020 Apr 16.

Antarctic Climate & Ecosystems Cooperative Research Centre Battery Point TAS Australia.

Southern Ocean waters are among the most vulnerable to ocean acidification. The projected increase in the CO level will cause changes in carbonate chemistry that are likely to be damaging to organisms inhabiting these waters. A meta-analysis was undertaken to examine the vulnerability of Antarctic marine biota occupying waters south of 60°S to ocean acidification. This meta-analysis showed that ocean acidification negatively affects autotrophic organisms, mainly phytoplankton, at CO levels above 1,000 μatm and invertebrates above 1,500 μatm, but positively affects bacterial abundance. The sensitivity of phytoplankton to ocean acidification was influenced by the experimental procedure used. Natural, mixed communities were more sensitive than single species in culture and showed a decline in chlorophyll concentration, productivity, and photosynthetic health, as well as a shift in community composition at CO levels above 1,000 μatm. Invertebrates showed reduced fertilization rates and increased occurrence of larval abnormalities, as well as decreased calcification rates and increased shell dissolution with any increase in CO level above 1,500 μatm. Assessment of the vulnerability of fish and macroalgae to ocean acidification was limited by the number of studies available. Overall, this analysis indicates that many marine organisms in the Southern Ocean are likely to be susceptible to ocean acidification and thereby likely to change their contribution to ecosystem services in the future. Further studies are required to address the poor spatial coverage, lack of community or ecosystem-level studies, and the largely unknown potential for organisms to acclimate and/or adapt to the changing conditions.
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http://dx.doi.org/10.1002/ece3.6205DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7246202PMC
May 2020

Correction to: Structure and function of the Arctic and Antarctic marine microbiota as revealed by metagenomics.

Microbiome 2020 Jun 1;8(1):77. Epub 2020 Jun 1.

College of Marine Life Sciences, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, 266003, China.

An amendment to this paper has been published and can be accessed via the original article.
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http://dx.doi.org/10.1186/s40168-020-00871-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7265220PMC
June 2020

Freezing, Melting, and Light Stress on the Photophysiology of Ice Algae: Ex Situ Incubation of the Ice Algal diatom Fragilariopsis cylindrus (Bacillariophyceae) Using an Ice Tank.

J Phycol 2020 10 7;56(5):1323-1338. Epub 2020 Jul 7.

Faculty of Environmental Earth Science, Hokkaido University, North 10 West 5, Kita-Ku, Sapporo, 060-0810, Japan.

Sea ice algae contribute up to 25% of the primary productivity of polar seas and seed large-scale ice-edge blooms. Fluctuations in temperature, salinity, and light associated with the freeze/thaw cycle can significantly impact the photophysiology of ice-associated taxa. The effects of multiple co-stressors (i.e., freezing temperature and high brine salinity or sudden high light exposure) on the photophysiology of ice algae were investigated in a series of ice tank experiments with the polar diatom Fragilariopsis cylindrus under different light intensities. When algal cells were frozen into the ice, the maximum quantum yield of photosystem II photochemistry (PSII; F /F ) decreased possibly due to the damage of PSII reaction centers and/or high brine salinity stress suppressing the reduction capacity downstream of PSII. Expression of the rbcL gene was highly up-regulated, suggesting that cells initiated strategies to enhance survival upon freezing in. Algae contained within the ice-matrix displayed similar levels of F /F regardless of the light treatments. Upon melting out, cells were exposed to high light (800 μmol photons · m  · s ), resulting in a rapid decline in F /F and significant up-regulation of non-photochemical quenching (NPQ). These results suggest that ice algae employed safety valves (i.e., NPQ) to maintain their photosynthetic capability during the sudden environmental changes. Our results infer that sea ice algae are highly adaptable when exposed to multiple co-stressors and that their success can, in part, be explained by the ability to rapidly modify their photosynthetic competence - a key factor contributing to algal bloom formation in the polar seas.
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http://dx.doi.org/10.1111/jpy.13036DOI Listing
October 2020

Insights into the Production and Role of Nitric Oxide in the Antarctic Sea-ice Diatom Fragilariopsis cylindrus.

J Phycol 2020 10 23;56(5):1196-1207. Epub 2020 Jun 23.

Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia.

Nitric oxide (NO) is widely recognized as an important transmitter molecule in biological systems, from animals to plants and microbes. However, the role of NO in marine photosynthetic microbes remains unclear and even less is known about the role of this metabolite in Antarctic sea-ice diatoms. Using a combination of microsensors, microfluidic chambers, and artificial sea-ice tanks, a basic mechanistic insight into NO's dynamics within the Antarctic sea-ice diatom Fragilariopsis cylindrus was obtained. Results suggest that NO production in F. cylindrus is nitrite-dependent via nitrate reductase. NO production was abolished upon exposure to light but could be induced in the light when normal photosynthetic electron flow was disrupted. The addition of exogenous NO to cellular suspensions of F. cylindrus negatively influenced growth, disrupted photosynthesis, and altered non-photochemical dissipation mechanisms. NO production was also observed when cells were exposed to stressful salinity and temperature regimes. These results suggest that during periods of environmental stress, NO could be produced in F. cylindrus as a "stress signa" molecule.
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http://dx.doi.org/10.1111/jpy.13027DOI Listing
October 2020

Isolation and complete genome sequence of a novel cyanophage, S-B05, infecting an estuarine Synechococcus strain: insights into environmental adaptation.

Arch Virol 2020 Jun 19;165(6):1397-1407. Epub 2020 Apr 19.

College of Marine Life Sciences, Ocean University of China, Qingdao, 266003, China.

A new cyanophage, S-B05, infecting a phycoerythrin-enriched (PE-type) Synechococcus strain was isolated by the liquid infection method, and its morphology and genetic features were examined. Phylogenetic analysis and morphological observation confirmed that S-B05 belongs to the family Myoviridae of the order Caudovirales. Its genome was fully sequenced, and found to be 208,857 bp in length with a G + C content of 39.9%. It contained 280 potential open reading frames and 123 conserved domains. Ninety-eight functional genes responsible for cyanophage structuring and packaging, DNA replication and regulation, and photosynthesis were identified, as well as genes encoding 172 hypothetical proteins. The genome of S-B05 is most similar to that of Prochlorococcus phage P-TIM68. Homologues of open reading frames of S-B05 can be found in various marine environments, as revealed by comparison of the S-B05 genome sequence to sequences in marine viral metagenomic databases. The presence of auxiliary metabolic genes (AMGs) related to photosynthesis, carbon metabolism, and phosphorus assimilation, as well as the phylogenetic relationships based on AMGs and the complete genome sequence, reflect the phage-host interaction mechanism or the specific adaptation strategy of the host to environmental conditions. The genome sequence information reported here will provide an important basis for further study of the adaptive evolution and ecological role of cyanophages and their hosts in the marine environment.
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http://dx.doi.org/10.1007/s00705-020-04595-6DOI Listing
June 2020

Structure and function of the Arctic and Antarctic marine microbiota as revealed by metagenomics.

Microbiome 2020 04 2;8(1):47. Epub 2020 Apr 2.

College of Marine Life Science, Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao, 266003, China.

Background: The Arctic and Antarctic are the two most geographically distant bioregions on earth. Recent sampling efforts and following metagenomics have shed light on the global ocean microbial diversity and function, yet the microbiota of polar regions has not been included in such global analyses.

Results: Here a metagenomic study of seawater samples (n = 60) collected from different depths at 28 locations in the Arctic and Antarctic zones was performed, together with metagenomes from the Tara Oceans. More than 7500 (19%) polar seawater-derived operational taxonomic units could not be identified in the Tara Oceans datasets, and more than 3,900,000 protein-coding gene orthologs had no hits in the Ocean Microbial Reference Gene Catalog. Analysis of 214 metagenome assembled genomes (MAGs) recovered from the polar seawater microbiomes, revealed strains that are prevalent in the polar regions while nearly undetectable in temperate seawater. Metabolic pathway reconstruction for these microbes suggested versatility for saccharide and lipids biosynthesis, nitrate and sulfate reduction, and CO fixation. Comparison between the Arctic and Antarctic microbiomes revealed that antibiotic resistance genes were enriched in the Arctic while functions like DNA recombination were enriched in the Antarctic.

Conclusions: Our data highlight the occurrence of dominant and locally enriched microbes in the Arctic and Antarctic seawater with unique functional traits for environmental adaption, and provide a foundation for analyzing the global ocean microbiome in a more complete perspective. Video abstract.
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http://dx.doi.org/10.1186/s40168-020-00826-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7119284PMC
April 2020

Ice Melting Can Change DMSP Production and Photosynthetic Activity of the Haptophyte Phaeocystis antarctica.

J Phycol 2020 06 2;56(3):761-774. Epub 2020 Apr 2.

Graduate School of Environmental Science/Faculty of Environmental Earth Science, Hokkaido University, North 10 West 5, Kita-ku, Sapporo, 060-0810, Japan.

Phaeocystis antarctica is an important primary producer in the Southern Ocean and plays roles in sulfur cycles through intracellular production of dimethylsulfoniopropionate (DMSP), a principal precursor of dimethyl sulfide (DMS). Haptophytes, including P. antarctica, are known to produce more DMSP than other phytoplankton groups such as diatoms and green algae, suggesting their important contribution to DMS concentrations in the Southern Ocean. We assessed how sea ice formation and melting affect photosynthesis and DMSP accumulation in P. antarctica both in seawater and in sea ice. Incubations were undertaken in an ice tank, which simulated sea ice formation and melting dynamics. The maximum quantum yield of photochemistry (F /F ) in photosystem II, as estimated from pulse-amplitude-modulated (PAM) fluorometry, was generally higher under low-light conditions than high-light conditions. Values of F /F , the relative maximum electron rate (rETR ), and photosynthetic efficiency (α) were lower in sea ice than in seawater, implying reduced photosynthetic function inside the sea ice. The reduction in photosynthetic function was probably due to the hypersaline environment in the brine channels. Total DMSP (DMSPt) concentration normalized by chlorophyll-a concentration was significantly higher in the sea ice than in the other environments, suggesting high accumulation of DMSP, probably due to its osmotic properties. F /F , specific growth rate, and DMSPt concentrations decreased with decreasing salinity with the lowest values found at a salinity of 22, that is, the lowest salinity tested. These results suggest that sea ice melting is responsible for a reduction in growth rate and DMSP production of P. antarctica.
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http://dx.doi.org/10.1111/jpy.12985DOI Listing
June 2020

Diversity of D-Amino Acid Utilizing Bacteria From Kongsfjorden, Arctic and the Metabolic Pathways for Seven D-Amino Acids.

Front Microbiol 2019 10;10:2983. Epub 2020 Jan 10.

State Key Laboratory of Microbial Technology, Institute of Marine Science and Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China.

D-amino acids (DAAs) are an important component of the refractory dissolved organic matter pool in the ocean. Microbes play a vital role in promoting the recycling of DAAs in the ocean. However, the diversity of marine DAA-utilizing bacteria and how they metabolize DAAs are seldom studied. Here, by enrichment culture with DAAs as the sole nitrogen source, bacteria of 12 families from three phyla were recovered from surface seawater and sediment from Kongsfjorden, Arctic, and seven DAA-utilizing bacterial strains were isolated. These strains have different DAA-utilizing abilities. Of the seven DAAs used, SM1922 and SM1927 were able to utilize seven and five of them, respectively, while the other strains were able to utilize only one or two. Based on genomic, transcriptional and biochemical analyses, the key genes involved in DAA metabolism in each strain were identified and the metabolic pathways for the seven DAAs in these marine bacteria were identified. Conversion of DAAs into α-keto acids is generally the main pathway in marine DAA-utilizing bacteria, which is performed by several key enzymes, including DAA oxidoreductases/dehydrogenases, D-serine ammonia-lyases, D-serine ammonia-lyase DSD1s and DAA transaminases. In addition, conversion of DAAs into LAAs is another pathway, which is performed by amino acid racemases. Among the identified key enzymes, D-serine ammonia-lyase DSD1 and Asp racemase are first found to be employed by bacteria for DAA utilization. These results shed light on marine DAA-utilizing bacteria and the involved DAA metabolism pathways, offering a better understanding of the DAA recycling in the ocean.
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http://dx.doi.org/10.3389/fmicb.2019.02983DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6965332PMC
January 2020

A predator-prey interaction between a marine Pseudoalteromonas sp. and Gram-positive bacteria.

Nat Commun 2020 01 15;11(1):285. Epub 2020 Jan 15.

State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, 266237, China.

Predator-prey interactions play important roles in the cycling of marine organic matter. Here we show that a Gram-negative bacterium isolated from marine sediments (Pseudoalteromonas sp. strain CF6-2) can kill Gram-positive bacteria of diverse peptidoglycan (PG) chemotypes by secreting the metalloprotease pseudoalterin. Secretion of the enzyme requires a Type II secretion system. Pseudoalterin binds to the glycan strands of Gram positive bacterial PG and degrades the PG peptide chains, leading to cell death. The released nutrients, including PG-derived D-amino acids, can then be utilized by strain CF6-2 for growth. Pseudoalterin synthesis is induced by PG degradation products such as glycine and glycine-rich oligopeptides. Genes encoding putative pseudoalterin-like proteins are found in many other marine bacteria. This study reveals a new microbial interaction in the ocean.
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http://dx.doi.org/10.1038/s41467-019-14133-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6962226PMC
January 2020

Significant Bacterial Distance-Decay Relationship in Continuous, Well-Connected Southern Ocean Surface Water.

Microb Ecol 2020 Jul 20;80(1):73-80. Epub 2019 Dec 20.

Institute of Marine Science and Technology, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China.

Recently, an increasing number of studies have focused on the biogeographic distribution of marine microorganisms. However, the extent to which geographic distance can affect marine microbial communities is still unclear, especially for the microbial communities in well-connected surface seawaters. In this study, the bacterial community compositions of 21 surface seawater samples, that were distributed over a distance of 7800 km, were surveyed to investigate how bacterial community similarity changes with increasing geographical distance. Proteobacteria and Bacteroidetes were the dominant bacterial phyla, with Proteobacteria accounting for 52.6-92.5% and Bacteroidetes comprising 3.5-46.9% of the bacterial communities. A significant bacterial distance-decay relationship was observed in the well-connected Southern Ocean surface seawater. The number of pairwise shared operational taxonomic units (OTUs), and community similarities tended to decrease with increasing geographic distance. Calculation of the similarity indices with all, abundant or rare OTUs did not affect the observed distance-decay relationship. Spatial distance can largely explain the observed bacterial community variation. This study shows that even in well-connected surface waters, bacterial distance-decay patterns can be found as long as the geographical distance is great enough. The biogeographic patterns should then be present for marine microorganisms considering the large size and complexity of the marine ecosystem.
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http://dx.doi.org/10.1007/s00248-019-01472-xDOI Listing
July 2020

Reconstruction of the Functional Ecosystem in the High Light, Low Temperature Union Glacier Region, Antarctica.

Front Microbiol 2019 18;10:2408. Epub 2019 Oct 18.

State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China.

Antarctica is covered by multiple larger glaciers with diverse extreme conditions. Microorganisms in Antarctic regions are primarily responsible for diverse biogeochemical processes. The identity and functionality of microorganisms from polar glaciers are defined. However, little is known about microbial communities from the high elevation glaciers. The Union Glacier, located in the inland of West Antarctica at 79°S, is a challenging environment for life to survive due to the high irradiance and low temperatures. Here, soil and rock samples were obtained from three high mountains (Rossman Cove, Charles Peak, and Elephant Head) adjacent to the Union Glacier. Using metagenomic analyses, the functional microbial ecosystem was analyzed through the reconstruction of carbon, nitrogen and sulfur metabolic pathways. A low biomass but diverse microbial community was found. Although archaea were detected, bacteria were dominant. Taxa responsible for carbon fixation were comprised of photoautotrophs (Cyanobacteria) and chemoautotrophs (mainly Alphaproteobacterial clades: , , and ). The main nitrogen fixation taxa were (Cyanobacteria), , and (Betaproteobacteria). Diverse sulfide-oxidizing and sulfate-reducing bacteria, fermenters, denitrifying microbes, methanogens, and methane oxidizers were also found. Putative producers provide organic carbon and nitrogen for the growth of other heterotrophic microbes. In the biogeochemical pathways, assimilation and mineralization of organic compounds were the dominant processes. Besides, a range of metabolic pathways and genes related to high irradiance, low temperature and other stress adaptations were detected, which indicate that the microbial communities had adapted to and could survive in this harsh environment. These results provide a detailed perspective of the microbial functional ecology of the Union Glacier area and improve our understanding of linkages between microbial communities and biogeochemical cycling in high Antarctic ecosystems.
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http://dx.doi.org/10.3389/fmicb.2019.02408DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6813960PMC
October 2019

Extracellular Enzyme Activity and Its Implications for Organic Matter Cycling in Northern Chinese Marginal Seas.

Front Microbiol 2019 13;10:2137. Epub 2019 Sep 13.

State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China.

Extracellular enzymes, initiating the degradation of organic macromolecules, are important functional components of marine ecosystems. Measuring seawater extracellular enzyme activity (EEA) can provide fundamental information for understanding the biogeochemical cycling of organic matter in the ocean. Here we investigate the patterns of EEA and the major factors affecting the seawater EEA of Chinese marginal seas. The geographic distribution of EEA along a latitudinal transect was examined and found to be associated with dissolved organic carbon. Compared with offshore waters, inshore waters had higher enzyme activity. All the tested substrates were hydrolyzed at different rates and phosphatase, β-glucosidase and protease contributed greatly to summed hydrolysis rates. For any particular enzyme activity, the contribution of dissolved to total EEA was strongly heterogenous between stations. Comparisons of hydrolysis rates of the polymers and their corresponding oligomers suggest that molecule size does not necessarily limit the turnover of marine organic matter. In addition, several typical enzyme-producing clades, such as Bacteroidetes, Planctomycetes, Chloroflexi, , , and , were detected in the environments. These enzyme-producing clades may be responsible for the production of different enzymes. Overall, each enzyme was found to flexibly respond to environmental conditions and were linked to microbial community composition. It is likely that this activity will profoundly affect organic matter cycling in the Chinese marginal seas.
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http://dx.doi.org/10.3389/fmicb.2019.02137DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6755343PMC
September 2019

Complete genomic sequence of bacteriophage P23: a novel Vibrio phage isolated from the Yellow Sea, China.

Virus Genes 2019 Dec 16;55(6):834-842. Epub 2019 Aug 16.

Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia.

A novel Vibrio phage, P23, belonging to the family Siphoviridae was isolated from the surface water of the Yellow Sea, China. The complete genome of this phage was determined. A one-step growth curve showed that the latent period was approximately 30 min, the burst size was 24 PFU/cell, and the rise period was 20 min. The phage is host specific and is stable over a range of pH (5-10) and temperatures (4-65 °C). Transmission electron microscopy showed that phage P23 can be categorized into the Siphoviridae family, with an icosahedral head of 60 nm and a long noncontractile tail of 144 nm. The genome consisted of a linear, double-stranded 40.063 kb DNA molecule with 42.5% G+C content and 72 putative open reading frames (ORFs) without tRNA. The predicted ORFs were classified into six functional groups, including DNA replication, regulation and nucleotide metabolism, transcription, phage packaging, phage structure, lysis, and hypothetical proteins. The Vibrio phage P23 genome is a new marine Siphoviridae-family phage genome that provides basic information for further molecular research on interaction mechanisms between bacteriophages and their hosts.
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http://dx.doi.org/10.1007/s11262-019-01699-3DOI Listing
December 2019

Characterization and Genome Analysis of a Novel Alteromonas Phage JH01 Isolated from the Qingdao Coast of China.

Curr Microbiol 2019 Nov 1;76(11):1256-1263. Epub 2019 Aug 1.

Institute for Marine and Antarctic Studies, University of Tasmania, TAS, Private Bag 129, Hobart, 7001, Australia.

A novel Alteromonas phage JH01, with the host strain identified to be Alteromonas marina SW-47(T), was isolated from the Qingdao coast during the summer of 2017. Transmission electron microscopy analysis showed that phage JH01 can be categorized into the Siphoviridae family, with an icosahedral head of 62 ± 5 nm and a long contractile tail of 254 ± 10 nm. The bioinformatic analysis shows that this phage consists of a linear, double-stranded 46,500 bp DNA molecule with a GC content of 44.39%, and 58 ORFs with no tRNA genes. The ORFs are classified into four groups, including phage packaging, phage structure, DNA replication and regulation, and hypothetical protein. The phylogenetic tree, constructed using neighbor-joining analysis, shows that phage JH01 has altitudinal homology with some Vibrio and Pseudoalteromonas phage B8b. Comparative analysis reveals the high similarity between phage JH01 and phage B8b. Additionally, our study of phage JH01 provides useful information for further research on the interaction between Alteromonas phages and their hosts.
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http://dx.doi.org/10.1007/s00284-019-01751-3DOI Listing
November 2019

Dark metabolism: a molecular insight into how the Antarctic sea-ice diatom Fragilariopsis cylindrus survives long-term darkness.

New Phytol 2019 07 7;223(2):675-691. Epub 2019 May 7.

Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, 7000, Tasmania, Australia.

Light underneath Antarctic sea-ice is below detectable limits for up to 4 months of the year. The ability of Antarctic sea-ice diatoms to survive this prolonged darkness relies on their metabolic capability. This study is the first to examine the proteome of a prominent sea-ice diatom in response to extended darkness, focusing on the protein-level mechanisms of dark survival. The Antarctic diatom Fragilariopsis cylindrus was grown under continuous light or darkness for 120 d. The whole cell proteome was quantitatively analysed by nano-LC-MS/MS to investigate metabolic changes that occur during sustained darkness and during recovery under illumination. Enzymes of metabolic pathways, particularly those involved in respiratory processes, tricarboxylic acid cycle, glycolysis, the Entner-Doudoroff pathway, the urea cycle and the mitochondrial electron transport chain became more abundant in the dark. Within the plastid, carbon fixation halted while the upper sections of the glycolysis, gluconeogenesis and pentose phosphate pathways became less active. We have discovered how F. cylindrus utilises an ancient alternative metabolic mechanism that enables its capacity for long-term dark survival. By sustaining essential metabolic processes in the dark, F. cylindrus retains the functionality of the photosynthetic apparatus, ensuring rapid recovery upon re-illumination.
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http://dx.doi.org/10.1111/nph.15843DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6617727PMC
July 2019

In-situ behavioural and physiological responses of Antarctic microphytobenthos to ocean acidification.

Sci Rep 2019 02 13;9(1):1890. Epub 2019 Feb 13.

School of Life and Environmental Sciences, University of Sydney, 2006, Sydney, Australia.

Ocean acidification (OA) is predicted to alter benthic marine community structure and function, however, there is a paucity of field experiments in benthic soft sediment communities and ecosystems. Benthic diatoms are important components of Antarctic coastal ecosystems, however very little is known of how they will respond to ocean acidification. Ocean acidification conditions were maintained by incremental computer controlled addition of high fCO seawater representing OA conditions predicted for the year 2100. Respiration chambers and PAM fluorescence techniques were used to investigate acute behavioural, photosynthetic and net production responses of benthic microalgae communities to OA in in-situ field experiments. We demonstrate how OA can modify behavioural ecology, which changes photo-physiology and net production of benthic microalgae. Ocean acidification treatments significantly altered behavioural ecology, which in turn altered photo-physiology. The ecological trends presented here have the potential to manifest into significant ecological change over longer time periods.
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http://dx.doi.org/10.1038/s41598-018-36233-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374400PMC
February 2019

Metagenomic Characterization of the Viral Community of the South Scotia Ridge.

Viruses 2019 01 24;11(2). Epub 2019 Jan 24.

College of Marine Life Sciences, Ocean University of China, Qingdao 266003, China.

Viruses are the most abundant biological entities in aquatic ecosystems and harbor an enormous amount of genetic diversity. Whereas their influence on marine ecosystems is widely acknowledged, current information about their diversity remains limited. We conducted a viral metagenomic analysis of water samples collected during the austral summer of 2016 from the South Scotia Ridge (SSR), near the Antarctic Peninsula. The taxonomic composition and diversity of the viral communities were investigated, and a functional assessment of the sequences was performed. Phylotypic analysis showed that most viruses belonged to the order , especially the family (41.92⁻48.7%), which is similar to the situation in the Pacific Ocean. Functional analysis revealed a relatively high frequency of phage-associated and metabolism genes. Phylogenetic analyses of phage TerL and Capsid_NCLDV (nucleocytoplasmic large DNA viruses) marker genes indicated that many sequences associated with and NCLDV were novel and distinct from known phage genomes. High virus virophage (Pgvv) signatures were found and complete and partial Pgvv-like were obtained, which influence host⁻virus interactions. Our study expands existing knowledge of viral communities and their diversities from the Antarctic region and provides basic data for further exploring polar microbiomes.
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http://dx.doi.org/10.3390/v11020095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6410227PMC
January 2019

Viral Diversity and Its Relationship With Environmental Factors at the Surface and Deep Sea of Prydz Bay, Antarctica.

Front Microbiol 2018 3;9:2981. Epub 2018 Dec 3.

College of Marine Life Sciences, Ocean University of China, Qingdao, China.

A viral metagenomic analysis of five surface and two bottom water (878 meters below surface, mbs, and 3,357 mbs) samples from Prydz Bay, was conducted during February-March 2015. The results demonstrated that most of the DNA viruses were dsDNA viruses (79.73-94.06%, except at PBI1, 37.51%). Of these, Caudovirales (, and ) phages were most abundant in surface seawater (67.67-71.99%), while nucleocytoplasmic large DNA viruses (NCLDVs) (, and accounted for >30% of dsDNA viruses) were most abundant in the bottom water (3,357 mbs). Of the ssDNA viruses, was the dominant family in PBI2, PBI3, PBOs, and PBI4b (57.09-87.55%), while (58.16%) was the dominant family in PBI1. phages (phi38:1 and phi10:1) and phage 11b, infecting the possible host strains affiliated with the family of the phylum , were abundant in surface water dsDNA viromes. The long contig (PBI2_1_C) from the viral metagenomes were most similar to the genome architectures of phage phi10:1 and phage 11b from the Arctic Ocean. Comparative analysis showed that the surface viral community of Prydz Bay could be clearly separated from other marine and freshwater environments. The deep sea viral community was similar to the deep sea viral metagenome at A Long-term Oligotrophic Habitat Assessment Station (ALOHA, at 22°45'N, 158°00'W). The multivariable analysis indicated that nutrients probably played an important role in shaping the local viral community structure. This study revealed the preliminary characteristics of the viral community in Prydz Bay, from both the surface and the deep sea. It provided evidence of the relationships between the virome and the environment in Prydz Bay and provided the first data from the deep sea viral community of the Southern Ocean.
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http://dx.doi.org/10.3389/fmicb.2018.02981DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6287040PMC
December 2018

Ocean acidification increases iodine accumulation in kelp-based coastal food webs.

Glob Chang Biol 2019 02 22;25(2):629-639. Epub 2018 Nov 22.

Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China.

Kelp are main iodine accumulators in the ocean, and their growth and photosynthesis are likely to benefit from elevated seawater CO levels due to ocean acidification. However, there are currently no data on the effects of ocean acidification on iodine metabolism in kelp. As key primary producers in coastal ecosystems worldwide, any change in their iodine metabolism caused by climate change will potentially have important consequences for global geochemical cycles of iodine, including iodine levels of coastal food webs that underpin the nutrition of billions of humans around the world. Here, we found that elevated pCO enhanced growth and increased iodine accumulation not only in the model kelp Saccharina japonica using both short-term laboratory experiment and long-term in situ mesocosms, but also in several other edible and ecologically significant seaweeds using long-term in situ mesocosms. Transcriptomic and proteomic analysis of S. japonica revealed that most vanadium-dependent haloperoxidase genes involved in iodine efflux during oxidative stress are down-regulated under increasing pCO , suggesting that ocean acidification alleviates oxidative stress in kelp, which might contribute to their enhanced growth. When consumed by abalone (Haliotis discus), elevated iodine concentrations in S. japonica caused increased iodine accumulation in abalone, accompanied by reduced synthesis of thyroid hormones. Thus, our results suggest that kelp will benefit from ocean acidification by a reduction in environmental stress however; iodine levels, in kelp-based coastal food webs will increase, with potential impacts on biogeochemical cycles of iodine in coastal ecosystems.
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http://dx.doi.org/10.1111/gcb.14467DOI Listing
February 2019

Vertical Distribution of Microbial Eukaryotes From Surface to the Hadal Zone of the Mariana Trench.

Front Microbiol 2018 28;9:2023. Epub 2018 Aug 28.

College of Marine Life Sciences, Ocean University of China, Qingdao, China.

Marine microbial eukaryotes are ubiquitous, comprised of phylogenetically diverse groups and play key roles in microbial food webs and global biogeochemical cycling. However, their vertical distribution in the deep sea has received little attention. In this study, we investigated the composition and diversity of the eukaryotes of both 0.2-3 μm and >3 μm size fractions from the surface to the hadal zone (8727 m) of the Mariana Trench using Illumina MiSeq sequencing for the 18S rDNA. The microbial eukaryotic community structure differed substantially across size fractions and depths. Operational taxonomic unit (OTU) richness in the >3 μm fraction was higher than that in the 0.2-3 μm fraction at the same depth. For the 0.2-3 μm fraction, sequences of Retaria (Rhizaria) were most abundant in the surface water (53.5%). Chrysophyceae (Stramenopiles) sequences dominated mostly in the samples from water depths below 1795 m. For the >3 μm fraction, sequences of Dinophyceae (Alveolata) were most abundant in surface waters (49.3%) and remained a significant proportion of total sequences at greater depths (9.8%, on average). Retaria sequences were abundant in samples of depths ≥1000 m. Amoebozoa and Apusozoa sequences were enriched in the hadal sample, comprising 38 and 20.4% of total sequences, respectively. Fungi (Opisthokonta) sequences were most abundant at 1759 m in both size fractions. Strong positive associations were found between Syndiniales (mainly MALV-I and MALV-II) and Retaria while negative associations were shown between MALV-II and Fungi in a co-occurrence analysis. This study compared the community structure of microbial eukaryotes in different zones in the deep sea and identified a distinct hadal community in the larger size fraction, suggesting the uniqueness of the eukaryotes in the biosphere in the Mariana Trench.
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http://dx.doi.org/10.3389/fmicb.2018.02023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6120995PMC
August 2018