Publications by authors named "Tatiana A Vishnivetskaya"

31 Publications

Comparative Metagenomics of the Active Layer and Permafrost from Low-Carbon Soil in the Canadian High Arctic.

Environ Sci Technol 2021 Sep 2;55(18):12683-12693. Epub 2021 Sep 2.

Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee 37996, United States.

Approximately 87% of the Arctic consists of low-organic carbon mineral soil, but knowledge of microbial activity in low-carbon permafrost (PF) and active layer soils remains limited. This study investigated the taxonomic composition and genetic potential of microbial communities at contrasting depths of the active layer (5, 35, and 65 cm below surface, bls) and PF (80 cm bls). We showed microbial communities in PF to be taxonomically and functionally different from those in the active layer. 16S rRNA gene sequence analysis revealed higher biodiversity in the active layer than in PF, and biodiversity decreased significantly with depth. The reconstructed 91 metagenome-assembled genomes showed that PF was dominated by heterotrophic, fermenting Bacteroidota using nitrite as their main electron acceptor. Prevalent microbes identified in the active layer belonged to bacterial taxa, gaining energy via aerobic respiration. Gene abundance in metagenomes revealed enrichment of genes encoding the plant-derived polysaccharide degradation and metabolism of nitrate and sulfate in PF, whereas genes encoding methane/ammonia oxidation, cold-shock protein, and two-component systems were generally more abundant in the active layer, particularly at 5 cm bls. The results of this study deepen our understanding of the low-carbon Arctic soil microbiome and improve prediction of the impacts of thawing PF.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.est.1c00802DOI Listing
September 2021

Eight Metagenome-Assembled Genomes Provide Evidence for Microbial Adaptation in 20,000- to 1,000,000-Year-Old Siberian Permafrost.

Appl Environ Microbiol 2021 09 10;87(19):e0097221. Epub 2021 Sep 10.

University of Tennessee, Knoxville, Tennessee, USA.

Permafrost microbes may be metabolically active in microscopic layers of liquid brines, even in ancient soil. Metagenomics can help discern whether permafrost microbes show adaptations to this environment. Thirty-three metagenome-assembled genomes (MAGs) were obtained from six depths (3.5 m to 20 m) of freshly cored permafrost from the Siberian Kolyma-Indigirka Lowland region. These soils have been continuously frozen for ∼20,000 to 1,000,000 years. Eight of these MAGs were ≥80% complete with <10% contamination and were taxonomically identified as , , , and within bacteria and within archaea. MAGs from these taxa have been obtained previously from nonpermafrost environments and have been suggested to show adaptations to long-term energy starvation, but they have never been explored in ancient permafrost. The permafrost MAGs had greater proportions in the Clusters of Orthologous Groups (COGs) categories of energy production and conversion and carbohydrate transport and metabolism than did their nonpermafrost counterparts. They also contained genes for trehalose synthesis, thymine metabolism, mevalonate biosynthesis, and cellulose degradation, which were less prevalent in nonpermafrost genomes. Many of these genes are involved in membrane stabilization and osmotic stress responses, consistent with adaptation to the anoxic, high-ionic-strength, cold environments of permafrost brine films. Our results suggest that this ancient permafrost contains DNA of high enough quality to assemble MAGs from microorganisms with adaptations to survive long-term freezing in this extreme environment. Permafrost around the world is thawing rapidly. Many scientists from a variety of disciplines have shown the importance of understanding what will happen to our ecosystem, commerce, and climate when permafrost thaws. The fate of permafrost microorganisms is connected to these predicted rapid environmental changes. Studying ancient permafrost with culture-independent techniques can give a glimpse into how these microorganisms function under these extreme low-temperature and low-energy conditions. This will facilitate understanding how they will change with the environment. This study presents genomic data from this unique environment ∼20,000 to 1,000,000 years of age.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AEM.00972-21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8432575PMC
September 2021

Genomic reconstruction of fossil and living microorganisms in ancient Siberian permafrost.

Microbiome 2021 05 17;9(1):110. Epub 2021 May 17.

Princeton University, B88, Guyot Hall, Princeton, NJ, 08544, USA.

Background: Total DNA (intracellular, iDNA and extracellular, eDNA) from ancient permafrost records the mixed genetic repository of the past and present microbial populations through geological time. Given the exceptional preservation of eDNA under perennial frozen conditions, typical metagenomic sequencing of total DNA precludes the discrimination between fossil and living microorganisms in ancient cryogenic environments. DNA repair protocols were combined with high throughput sequencing (HTS) of separate iDNA and eDNA fraction to reconstruct metagenome-assembled genomes (MAGs) from ancient microbial DNA entrapped in Siberian coastal permafrost.

Results: Despite the severe DNA damage in ancient permafrost, the coupling of DNA repair and HTS resulted in a total of 52 MAGs from sediments across a chronosequence (26-120 kyr). These MAGs were compared with those derived from the same samples but without utilizing DNA repair protocols. The MAGs from the youngest stratum showed minimal DNA damage and thus likely originated from viable, active microbial species. Many MAGs from the older and deeper sediment appear related to past aerobic microbial populations that had died upon freezing. MAGs from anaerobic lineages, including Asgard archaea, however exhibited minimal DNA damage and likely represent extant living microorganisms that have become adapted to the cryogenic and anoxic environments. The integration of aspartic acid racemization modeling and metaproteomics further constrained the metabolic status of the living microbial populations. Collectively, combining DNA repair protocols with HTS unveiled the adaptive strategies of microbes to long-term survivability in ancient permafrost.

Conclusions: Our results indicated that coupling of DNA repair protocols with simultaneous sequencing of iDNA and eDNA fractions enabled the assembly of MAGs from past and living microorganisms in ancient permafrost. The genomic reconstruction from the past and extant microbial populations expanded our understanding about the microbial successions and biogeochemical alterations from the past paleoenvironment to the present-day frozen state. Furthermore, we provided genomic insights into long-term survival mechanisms of microorganisms under cryogenic conditions through geological time. The combined strategies in this study can be extrapolated to examine other ancient non-permafrost environments and constrain the search for past and extant extraterrestrial life in permafrost and ice deposits on Mars. Video abstract.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s40168-021-01057-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8130349PMC
May 2021

Insights into community of photosynthetic microorganisms from permafrost.

FEMS Microbiol Ecol 2020 11;96(12)

Soil Cryology Laboratory, Institute of Physicochemical and Biological Problems in Soil Science, Institutskaya Street, Bldg. 2, Pushchino, Russia.

This work integrates cultivation studies of Siberian permafrost and analyses of metagenomes from different locations in the Arctic with the aim of obtaining insights into the community of photosynthetic microorganisms in perennially frozen deposits. Cyanobacteria and microalgae have been described in Arctic aquatic and surface soil environments, but their diversity and ability to withstand harsh conditions within the permafrost are still largely unknown. Community structure of photosynthetic organisms in permafrost sediments was explored using Arctic metagenomes available through the MG-RAST. Sequences affiliated with cyanobacteria represented from 0.25 to 3.03% of total sequences, followed by sequences affiliated with Streptophyta (algae and vascular plants) 0.01-0.45% and Chlorophyta (green algae) 0.01-0.1%. Enrichment and cultivation approaches revealed that cyanobacteria and green algae survive in permafrost and they could be revived during prolonged incubation at low light intensity. Among photosynthetic microorganisms isolated from permafrost, the filamentous Oscillatoria-like cyanobacteria and unicellular green algae of the genus Chlorella were dominant. Our findings suggest that permafrost cyanobacteria and green algae are expected to be effective members of the re-assembled community after permafrost thawing and soil collapse.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/femsec/fiaa229DOI Listing
November 2020

Thaumarchaea Genome Sequences from a High Arctic Active Layer.

Microbiol Resour Announc 2020 May 21;9(21). Epub 2020 May 21.

Department of Geosciences, Princeton University, Princeton, New Jersey, USA

The role of archaeal ammonia oxidizers often exceeds that of bacterial ammonia oxidizers in marine and terrestrial environments but has been understudied in permafrost, where thawing has the potential to release ammonia. Here, three thaumarchaea genomes were assembled and annotated from metagenomic data sets from carbon-poor Canadian High Arctic active-layer cryosols.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/MRA.00326-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242670PMC
May 2020

Metagenome-Assembled Genome of USCα AHI, a Potential High-Affinity Methanotroph from Axel Heiberg Island, Canadian High Arctic.

Microbiol Resour Announc 2019 Nov 14;8(46). Epub 2019 Nov 14.

Department of Geosciences, Princeton University, Princeton, New Jersey, USA

Metagenomic sequencing of active-layer cryosols from the Canadian High Arctic has yielded a nearly complete genome for an atmospheric CH-oxidizing bacterium belonging to upland soil cluster α (USCα). This genome contains genes involved in CH metabolism, H metabolism, and multiple carbon assimilation pathways.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/MRA.01178-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6856278PMC
November 2019

Draft Genome Sequence of Microbacterium sp. Gd 4-13, Isolated from Gydanskiy Peninsula Permafrost Sediments of Marine Origin.

Microbiol Resour Announc 2019 Oct 3;8(40). Epub 2019 Oct 3.

Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, Pushchino, Russia.

Here, we report the draft genome sequence of sp. strain Gd 4-13, isolated from late Pleistocene permafrost of marine origin located on the Gydanskiy Peninsula. Genome sequence analysis was performed to understand strain survivability mechanisms under permafrost conditions and to expand biotechnology applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/MRA.00889-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6776773PMC
October 2019

Methanogens in the Antarctic Dry Valley permafrost.

FEMS Microbiol Ecol 2018 08;94(8)

Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences, Pushchino, 142290, Russia.

Polar permafrost is at the forefront of climate change, yet only a few studies have enriched the native methane-producing microbes that might provide positive feedbacks to climate change. Samples Ant1 and Ant2, collected in Antarctic Miers Valley from permafrost sediments, with and without biogenic methane, respectively, were evaluated for methanogenic activity and presence of methanogens. After a one-year incubation of both samples under anaerobic conditions, methane production was observed only at room temperature in microcosm Ant1 with CO2/H2 (20/80) as carbon and energy sources and was monitored during the subsequent 10 years. The concentration of methane in the headspace of microcosm Ant1 changed from 0.8% to a maximum of 45%. Archaeal 16S rRNA genes from microcosm Ant1 were related to psychrotolerant Methanosarcina lacustris. Repeated efforts at achieving a pure culture of this organism were unsuccessful. Metagenomic reads obtained for the methane-producing microcosm Ant1 were assembled and resulted in a 99.84% complete genome affiliated with the genus Methanosarcina. The metagenome assembled genome contained cold-adapted enzymes and pathways suggesting that the novel uncultured Methanosarcina sp. Ant1 is adapted to sub-freezing conditions in permafrost. This is the first methanogen genome reported from the 15 000 years old permafrost of the Antarctic Dry Valleys.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/femsec/fiy109DOI Listing
August 2018

Microbial community structure with trends in methylation gene diversity and abundance in mercury-contaminated rice paddy soils in Guizhou, China.

Environ Sci Process Impacts 2018 Apr;20(4):673-685

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6036, USA.

Paddy soils from mercury (Hg)-contaminated rice fields in Guizhou, China were studied with respect to total mercury (THg) and methylmercury (MeHg) concentrations as well as Bacterial and Archaeal community composition. Total Hg (0.25-990 μg g-1) and MeHg (1.3-30.5 ng g-1) varied between samples. Pyrosequencing (454 FLX) of the hypervariable v1-v3 regions of the 16S rRNA genes showed that Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, Euryarchaeota, and Crenarchaeota were dominant in all samples. The Bacterial α-diversity was higher in samples with relatively Low THg and MeHg and decreased with increasing THg and MeHg concentrations. In contrast, Archaeal α-diversity increased with increasing of MeHg concentrations but did not correlate with changes in THg concentrations. Overall, the methylation gene hgcAB copy number increased with both increasing THg and MeHg concentrations. The microbial communities at High THg and High MeHg appear to be adapted by species that are both Hg resistant and carry hgcAB genes for MeHg production. The relatively high abundance of both sulfate-reducing δ-Proteobacteria and methanogenic Archaea, as well as their positive correlations with increasing THg and MeHg concentrations, suggests that these microorganisms are the primary Hg-methylators in the rice paddy soils in Guizhou, China.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c7em00558jDOI Listing
April 2018

Draft Genome Sequence of Antarctic Methanogen Enriched from Dry Valley Permafrost.

Genome Announc 2016 Dec 8;4(6). Epub 2016 Dec 8.

Department of Microbiology, University of Tennessee, Knoxville, Tennessee, USA

A genomic reconstruction belonging to the genus Methanosarcina was assembled from metagenomic data from a methane-producing enrichment of Antarctic permafrost. This is the first methanogen genome reported from permafrost of the Dry Valleys and can help shed light on future climate-affected methane dynamics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/genomeA.01362-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5146446PMC
December 2016

Metagenomes from thawing low-soil-organic-carbon mineral cryosols and permafrost of the canadian high arctic.

Genome Announc 2014 Nov 20;2(6). Epub 2014 Nov 20.

Microbial release of greenhouse gases from thawing permafrost is a global concern. Seventy-six metagenomes were generated from low-soil-organic-carbon mineral cryosols from Axel Heiberg Island, Nunavut, Canada, during a controlled thawing experiment. Permafrost thawing resulted in an increase in anaerobic fermenters and sulfate-reducing bacteria but not methanogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/genomeA.01217-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4239366PMC
November 2014

Draft genome sequences of 10 strains of the genus exiguobacterium.

Genome Announc 2014 Oct 16;2(5). Epub 2014 Oct 16.

DOE Joint Genome Institute, Walnut Creek, California, USA.

High-quality draft genome sequences were determined for 10 Exiguobacterium strains in order to provide insight into their evolutionary strategies for speciation and environmental adaptation. The selected genomes include psychrotrophic and thermophilic species from a range of habitats, which will allow for a comparison of metabolic pathways and stress response genes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/genomeA.01058-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4200161PMC
October 2014

Community analysis of plant biomass-degrading microorganisms from Obsidian Pool, Yellowstone National Park.

Microb Ecol 2015 Feb 16;69(2):333-45. Epub 2014 Oct 16.

BioEnergy Science Center, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.

The conversion of lignocellulosic biomass into biofuels can potentially be improved by employing robust microorganisms and enzymes that efficiently deconstruct plant polysaccharides at elevated temperatures. Many of the geothermal features of Yellowstone National Park (YNP) are surrounded by vegetation providing a source of allochthonic material to support heterotrophic microbial communities adapted to utilize plant biomass as a primary carbon and energy source. In this study, a well-known hot spring environment, Obsidian Pool (OBP), was examined for potential biomass-active microorganisms using cultivation-independent and enrichment techniques. Analysis of 33,684 archaeal and 43,784 bacterial quality-filtered 16S rRNA gene pyrosequences revealed that archaeal diversity in the main pool was higher than bacterial; however, in the vegetated area, overall bacterial diversity was significantly higher. Of notable interest was a flooded depression adjacent to OBP supporting a stand of Juncus tweedyi, a heat-tolerant rush commonly found growing near geothermal features in YNP. The microbial community from heated sediments surrounding the plants was enriched in members of the Firmicutes including potentially (hemi)cellulolytic bacteria from the genera Clostridium, Anaerobacter, Caloramator, Caldicellulosiruptor, and Thermoanaerobacter. Enrichment cultures containing model and real biomass substrates were established at a wide range of temperatures (55-85 °C). Microbial activity was observed up to 80 °C on all substrates including Avicel, xylan, switchgrass, and Populus sp. Independent of substrate, Caloramator was enriched at lower (<65 °C) temperatures while highly active cellulolytic bacteria Caldicellulosiruptor were dominant at high (>65 °C) temperatures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00248-014-0500-8DOI Listing
February 2015

Improved yield of high molecular weight DNA coincides with increased microbial diversity access from iron oxide cemented sub-surface clay environments.

PLoS One 2014 17;9(7):e102826. Epub 2014 Jul 17.

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America.

Despite over three decades of progress, extraction of high molecular weight (HMW) DNA from high clay soils or iron oxide cemented clay has remained challenging. HMW DNA is desirable for next generation sequencing as it yields the most comprehensive coverage. Several DNA extraction procedures were compared from samples that exhibit strong nucleic acid adsorption. pH manipulation or use of alternative ion solutions offered no improvement in nucleic acid recovery. Lysis by liquid N2 grinding in concentrated guanidine followed by concentrated sodium phosphate extraction supported HMW DNA recovery from clays high in iron oxides. DNA recovered using 1 M sodium phosphate buffer (PB) as a competitive desorptive wash was 15.22±2.33 µg DNA/g clay, with most DNA consisting of >20 Kb fragments, compared to 2.46±0.25 µg DNA/g clay with the Powerlyzer system (MoBio). Increasing PB concentration in the lysis reagent coincided with increasing DNA fragment length during initial extraction. Rarefaction plots of 16S rRNA (V1-V3 region) pyrosequencing from A-horizon and clay soils showed an ∼80% and ∼400% larger accessed diversity compared to the Powerlyzer soil DNA system, respectively. The observed diversity from the Firmicutes showed the strongest increase with >3-fold more operational taxonomic units (OTU) recovered.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0102826PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4102596PMC
November 2015

Commercial DNA extraction kits impact observed microbial community composition in permafrost samples.

FEMS Microbiol Ecol 2014 Jan 17;87(1):217-30. Epub 2013 Oct 17.

University of Tennessee, Knoxville, TN, USA.

The total community genomic DNA (gDNA) from permafrost was extracted using four commercial DNA extraction kits. The gDNAs were compared using quantitative real-time PCR (qPCR) targeting 16S rRNA genes and bacterial diversity analyses obtained via 454 pyrosequencing of the 16S rRNA (V3 region) amplified in single or nested PCR. The FastDNA(®) SPIN (FDS) Kit provided the highest gDNA yields and 16S rRNA gene concentrations, followed by MoBio PowerSoil(®) (PS) and MoBio PowerLyzer™ (PL) kits. The lowest gDNA yields and 16S rRNA gene concentrations were from the Meta-G-Nome™ (MGN) DNA Isolation Kit. Bacterial phyla identified in all DNA extracts were similar to that found in other soils and were dominated by Actinobacteria, Firmicutes, Gemmatimonadetes, Proteobacteria, and Acidobacteria. Weighted UniFrac and statistical analyses indicated that bacterial community compositions derived from FDS, PS, and PL extracts were similar to each other. However, the bacterial community structure from the MGN extracts differed from other kits exhibiting higher proportions of easily lysed β- and γ-Proteobacteria and lower proportions of Actinobacteria and Methylocystaceae important in carbon cycling. These results indicate that gDNA yields differ between the extraction kits, but reproducible bacterial community structure analysis may be accomplished using gDNAs from the three bead-beating lysis extraction kits.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/1574-6941.12219DOI Listing
January 2014

Microbial communities involved in biological ammonium removal from coal combustion wastewaters.

Microb Ecol 2013 Jul 13;66(1):49-59. Epub 2013 Jan 13.

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6036, USA.

The efficiency of a novel integrated treatment system for biological removal of ammonium, nitrite, nitrate, and heavy metals from fossil power plant effluent was evaluated. Microbial communities were analyzed using bacterial and archaeal 16S rRNA gene clone libraries (Sanger sequences) and 454 pyrosequencing technology. While seasonal changes in microbial community composition were observed, the significant (P = 0.001) changes in bacterial and archaeal communities were consistent with variations in ammonium concentration. Phylogenetic analysis of 16S rRNA gene sequences revealed an increase of potential ammonium-oxidizing bacteria (AOB), Nitrosomonas, Nitrosococcus, Planctomycetes, and OD1, in samples with elevated ammonium concentration. Other bacteria, such as Nitrospira, Nitrococcus, Nitrobacter, Thiobacillus, ε-Proteobacteria, Firmicutes, and Acidobacteria, which play roles in nitrification and denitrification, were also detected. The AOB oxidized 56 % of the ammonium with the concomitant increase in nitrite and ultimately nitrate in the trickling filters at the beginning of the treatment system. Thermoprotei within the phylum Crenarchaeota thrived in the splitter box and especially in zero-valent iron extraction trenches, where an additional 25 % of the ammonium was removed. The potential ammonium-oxidizing Archaea (AOA) (Candidatus Nitrosocaldus) were detected towards the downstream end of the treatment system. The design of an integrated treatment system consisting of trickling filters, zero-valent iron reaction cells, settling pond, and anaerobic wetlands was efficient for the biological removal of ammonium and several other contaminants from wastewater generated at a coal burning power plant equipped with selective catalytic reducers for nitrogen oxide removal.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00248-012-0152-5DOI Listing
July 2013

Anaerobic high-throughput cultivation method for isolation of thermophiles using biomass-derived substrates.

Methods Mol Biol 2012 ;908:153-68

Oak Ridge National Laboratory, BioEnergy Science Center, Oak Ridge, TN, USA.

Flow cytometry (FCM) techniques have been developed for sorting mesophilic organisms, but the difficulty increases if the target microbes are thermophilic anaerobes. We demonstrate a reliable, high-throughput method of screening thermophilic anaerobic organisms using FCM and 96-well plates for growth on biomass-relevant substrates. The method was tested using the cellulolytic thermophiles Clostridium thermocellum (T(opt) = 55 °C), Caldicellulosiruptor obsidiansis (T(opt) = 78 °C) and the fermentative hyperthermophiles, Pyrococcus furiosus (T(opt) = 100 °C) and Thermotoga maritima (T(opt) = 80 °C). Multi-well plates were incubated at various temperatures for approximately 72-120 h and then tested for growth. Positive growth resulting from single cells sorted into individual wells containing an anaerobic medium was verified by OD(600). Depending on the growth substrate, up to 80 % of the wells contained viable cultures, which could be transferred to fresh media. This method was used to isolate thermophilic microbes from Rabbit Creek, Yellowstone National Park (YNP), Wyoming. Substrates for enrichment cultures including crystalline cellulose (Avicel), xylan (from Birchwood), pretreated switchgrass and Populus were used to cultivate organisms that may be of interest to lignocellulosic biofuel production.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/978-1-61779-956-3_15DOI Listing
December 2012

Complete genome sequence of the Thermophilic Bacterium Exiguobacterium sp. AT1b.

J Bacteriol 2011 Jun 1;193(11):2880-1. Epub 2011 Apr 1.

The University of Tennessee, Center for Environmental Biotechnology, 676 Dabney-Buehler Hall, Knoxville, TN 37996-1605, USA.

Here we present the genome of strain Exiguobacterium sp. AT1b, a thermophilic member of the genus Exiguobacterium whose representatives were isolated from various environments along a thermal and physicochemical gradient. This genome was sequenced to be a comparative resource for the study of thermal adaptation with a psychroactive representative of the genus, Exiguobacterium sibiricum strain 255-15, that was previously sequenced by the U.S. Department of Energy's (DOE's) Joint Genome Institute (JGI) (http://genome.ornl.gov/microbial/exig/).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JB.00303-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3133134PMC
June 2011

Enhancement in current density and energy conversion efficiency of 3-dimensional MFC anodes using pre-enriched consortium and continuous supply of electron donors.

Bioresour Technol 2011 Apr 25;102(8):5098-104. Epub 2011 Jan 25.

BioSciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6226, USA.

Using a pre-enriched microbial consortium as the inoculum and continuous supply of carbon source, improvement in performance of a three-dimensional, flow-through MFC anode utilizing ferricyanide cathode was investigated. The power density increased from 170 W/m(3) (1800 mW/m(2)) to 580 W/m(3) (6130 mW/m(2)), when the carbon loading increased from 2.5 g/l-day to 50 g/l-day. The coulombic efficiency (CE) decreased from 90% to 23% with increasing carbon loading. The CEs are among the highest reported for glucose and lactate as the substrate with the maximum current density reaching 15.1A/m(2). This suggests establishment of a very high performance exoelectrogenic microbial consortium at the anode. A maximum energy conversion efficiency of 54% was observed at a loading of 2.5 g/l-day. Biological characterization of the consortium showed presence of Burkholderiales and Rhodocyclales as the dominant members. Imaging of the biofilms revealed thinner biofilms compared to the inoculum MFC, but a 1.9-fold higher power density.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biortech.2011.01.045DOI Listing
April 2011

Mercury and other heavy metals influence bacterial community structure in contaminated Tennessee streams.

Appl Environ Microbiol 2011 Jan 5;77(1):302-11. Epub 2010 Nov 5.

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6036, USA.

High concentrations of uranium, inorganic mercury [Hg(II)], and methylmercury (MeHg) have been detected in streams located in the Department of Energy reservation in Oak Ridge, TN. To determine the potential effects of the surface water contamination on the microbial community composition, surface stream sediments were collected 7 times during the year, from 5 contaminated locations and 1 control stream. Fifty-nine samples were analyzed for bacterial community composition and geochemistry. Community characterization was based on GS 454 FLX pyrosequencing with 235 Mb of 16S rRNA gene sequence targeting the V4 region. Sorting and filtering of the raw reads resulted in 588,699 high-quality sequences with lengths of >200 bp. The bacterial community consisted of 23 phyla, including Proteobacteria (ranging from 22.9 to 58.5% per sample), Cyanobacteria (0.2 to 32.0%), Acidobacteria (1.6 to 30.6%), Verrucomicrobia (3.4 to 31.0%), and unclassified bacteria. Redundancy analysis indicated no significant differences in the bacterial community structure between midchannel and near-bank samples. Significant correlations were found between the bacterial community and seasonal as well as geochemical factors. Furthermore, several community members within the Proteobacteria group that includes sulfate-reducing bacteria and within the Verrucomicrobia group appeared to be associated positively with Hg and MeHg. This study is the first to indicate an influence of MeHg on the in situ microbial community and suggests possible roles of these bacteria in the Hg/MeHg cycle.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AEM.01715-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3019708PMC
January 2011

Characterization of archaeal community in contaminated and uncontaminated surface stream sediments.

Microb Ecol 2010 Nov 20;60(4):784-95. Epub 2010 Aug 20.

Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6342, USA.

Archaeal communities from mercury and uranium-contaminated freshwater stream sediments were characterized and compared to archaeal communities present in an uncontaminated stream located in the vicinity of Oak Ridge, TN, USA. The distribution of the Archaea was determined by pyrosequencing analysis of the V4 region of 16S rRNA amplified from 12 streambed surface sediments. Crenarchaeota comprised 76% of the 1,670 archaeal sequences and the remaining 24% were from Euryarchaeota. Phylogenetic analysis further classified the Crenarchaeota as a Freshwater Group, Miscellaneous Crenarchaeota group, Group I3, Rice Cluster VI and IV, Marine Group I and Marine Benthic Group B; and the Euryarchaeota into Methanomicrobiales, Methanosarcinales, Methanobacteriales, Rice Cluster III, Marine Benthic Group D, Deep Sea Hydrothermal Vent Euryarchaeota 1 and Eury 5. All groups were previously described. Both hydrogen- and acetate-dependent methanogens were found in all samples. Most of the groups (with 60% of the sequences) described in this study were not similar to any cultivated isolates, making it difficult to discern their function in the freshwater microbial community. A significant decrease in the number of sequences, as well as in the diversity of archaeal communities was found in the contaminated sites. The Marine Group I, including the ammonia oxidizer Nitrosopumilus maritimus, was the dominant group in both mercury and uranium/nitrate-contaminated sites. The uranium-contaminated site also contained a high concentration of nitrate, thus Marine Group I may play a role in nitrogen cycle.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00248-010-9734-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2974187PMC
November 2010

Microbial community changes in response to ethanol or methanol amendments for U(VI) reduction.

Appl Environ Microbiol 2010 Sep 2;76(17):5728-35. Epub 2010 Jul 2.

Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.

Microbial community responses to ethanol, methanol, and methanol plus humics amendments in relationship to U(VI) bioreduction were studied in laboratory microcosm experiments using sediments and ground water from a uranium-contaminated site in Oak Ridge, TN. The type of carbon source added, the duration of incubation, and the sampling site influenced the bacterial community structure upon incubation. Analysis of 16S rRNA gene clone libraries indicated that (i) bacterial communities found in ethanol- and methanol-amended samples with U(VI) reduction were similar due to the presence of Deltaproteobacteria and Betaproteobacteria (members of the families Burkholderiaceae, Comamonadaceae, Oxalobacteraceae, and Rhodocyclaceae); (ii) methanol-amended samples without U(VI) reduction exhibited the lowest diversity and the bacterial community contained 69.2 to 92.8% of the family Methylophilaceae; and (iii) the addition of humics resulted in an increase of phylogenetic diversity of Betaproteobacteria (Rodoferax, Polaromonas, Janthinobacterium, Methylophilales, and unclassified) and Firmicutes (Desulfosporosinus and Clostridium).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AEM.00308-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2935046PMC
September 2010

Microbial communities in subpermafrost saline fracture water at the Lupin Au mine, Nunavut, Canada.

Microb Ecol 2009 Nov 1;58(4):786-807. Epub 2009 Jul 1.

Department of Geosciences, Princeton University, Princeton, 08544, NJ 08544, USA.

We report the first investigation of a deep subpermafrost microbial ecosystem, a terrestrial analog for the Martian subsurface. Our multidisciplinary team analyzed fracture water collected at 890 and 1,130 m depths beneath a 540-m-thick permafrost layer at the Lupin Au mine (Nunavut, Canada). 14C, 3H, and noble gas isotope analyses suggest that the Na-Ca-Cl, suboxic, fracture water represents a mixture of geologically ancient brine, approximately25-kyr-old, meteoric water and a minor modern talik-water component. Microbial planktonic concentrations were approximately10(3) cells mL(-1). Analysis of the 16S rRNA gene from extracted DNA and enrichment cultures revealed 42 unique operational taxonomic units in 11 genera with Desulfosporosinus, Halothiobacillus, and Pseudomonas representing the most prominent phylotypes and failed to detect Archaea. The abundance of terminally branched and midchain-branched saturated fatty acids (5 to 15 mol%) was consistent with the abundance of Gram-positive bacteria in the clone libraries. Geochemical data, the ubiquinone (UQ) abundance (3 to 11 mol%), and the presence of both aerobic and anaerobic bacteria indicated that the environment was suboxic, not anoxic. Stable sulfur isotope analyses of the fracture water detected the presence of microbial sulfate reduction, and analyses of the vein-filling pyrite indicated that it was in isotopic equilibrium with the dissolved sulfide. Free energy calculations revealed that sulfate reduction and sulfide oxidation via denitrification and not methanogenesis were the most thermodynamically viable consistent with the principal metabolisms inferred from the 16S rRNA community composition and with CH4 isotopic compositions. The sulfate-reducing bacteria most likely colonized the subsurface during the Pleistocene or earlier, whereas aerobic bacteria may have entered the fracture water networks either during deglaciation prior to permafrost formation 9,000 years ago or from the nearby talik through the hydrologic gradient created during mine dewatering. Although the absence of methanogens from this subsurface ecosystem is somewhat surprising, it may be attributable to an energy bottleneck that restricts their migration from surface permafrost deposits where they are frequently reported. These results have implications for the biological origin of CH4 on Mars.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00248-009-9553-5DOI Listing
November 2009

The Exiguobacterium genus: biodiversity and biogeography.

Extremophiles 2009 May 19;13(3):541-55. Epub 2009 Apr 19.

North Carolina State University, Raleigh, NC 27695, USA.

Bacteria of the genus Exiguobacterium are low G + C, Gram-positive facultative anaerobes that have been repeatedly isolated from ancient Siberian permafrost. In addition, Exiguobacterium spp. have been isolated from markedly diverse sources, including Greenland glacial ice, hot springs at Yellowstone National Park, the rhizosphere of plants, and the environment of food processing plants. Strains of this hereto little known bacterium that have been retrieved from such different (and often extreme) environments are worthy of attention as they are likely to be specifically adapted to such environments and to carry variations in the genome which may correspond to psychrophilic and thermophilic adaptations. However, comparative genomic investigations of Exiguobacterium spp. from different sources have been limited. In this study, we employed different molecular approaches for the comparative analysis of 24 isolates from markedly diverse environments including ancient Siberian permafrost and hot springs at Yellowstone National Park. Pulsed-field gel electrophoresis (PFGE) with I-CeuI (an intron-encoded endonuclease), AscI and NotI were optimized for the determination of genomic fingerprints of nuclease-producing isolates. The application of a DNA macroarray for 82 putative stress-response genes yielded strain-specific hybridization profiles. Cluster analyses of 16S rRNA gene sequence data, PFGE I-CeuI restriction patterns and hybridization profiles suggested that Exiguobacterium strains formed two distinct divisions that generally agreed with temperature ranges for growth. With few exceptions (e.g., Greenland ice isolate GIC31), psychrotrophic and thermophilic isolates belonged to different divisions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00792-009-0243-5DOI Listing
May 2009

Controlling accumulation of fermentation inhibitors in biorefinery recycle water using microbial fuel cells.

Biotechnol Biofuels 2009 Apr 1;2(1). Epub 2009 Apr 1.

BioSciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6226, USA.

Background: Microbial fuel cells (MFC) and microbial electrolysis cells are electrical devices that treat water using microorganisms and convert soluble organic matter into electricity and hydrogen, respectively. Emerging cellulosic biorefineries are expected to use large amounts of water during production of ethanol. Pretreatment of cellulosic biomass results in production of fermentation inhibitors which accumulate in process water and make the water recycle process difficult. Use of MFCs to remove the inhibitory sugar and lignin degradation products from recycle water is investigated in this study.

Results: Use of an MFC to reduce the levels of furfural, 5-hydroxymethylfurfural, vanillic acid, 4-hydroxybenzaldehyde and 4-hydroxyacetophenone while simultaneously producing electricity is demonstrated here. An integrated MFC design approach was used which resulted in high power densities for the MFC, reaching up to 3700 mW/m2 (356 W/m3 net anode volume) and a coulombic efficiency of 69%. The exoelectrogenic microbial consortium enriched in the anode was characterized using a 16S rRNA clone library method. A unique exoelectrogenic microbial consortium dominated by delta-Proteobacteria (50%), along with beta-Proteobacteria (28%), alpha-Proteobacteria (14%), gamma-Proteobacteria (6%) and others was identified. The consortium demonstrated broad substrate specificity, ability to handle high inhibitor concentrations (5 to 20 mM) with near complete removal, while maintaining long-term stability with respect to power production.

Conclusion: Use of MFCs for removing fermentation inhibitors has implications for: 1) enabling higher ethanol yields at high biomass loading in cellulosic ethanol biorefineries, 2) improved water recycle and 3) electricity production up to 25% of total biorefinery power needs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1754-6834-2-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2670826PMC
April 2009

Donor-dependent extent of uranium reduction for bioremediation of contaminated sediment microcosms.

J Environ Qual 2009 Jan-Feb;38(1):53-60. Epub 2009 Jan 13.

Oak Ridge National Lab., Biosciences Division, P.O. Box 2008, Oak Ridge, TN 37831-6038, USA.

Bioremediation of uranium was investigated in microcosm experiments containing contaminated sediments from Oak Ridge, Tennessee to explore the importance of electron donor selection for uranium reduction rate and extent. In these experiments, all of the electron donors, including ethanol, glucose, methanol, and methanol with added humic acids, stimulated the reduction and immobilization of aqueous uranium by the indigenous microbial community. Uranium loss from solution began after the completion of nitrate reduction but essentially concurrent with sulfate reduction. When electron donor concentrations were normalized for their equivalent electron donor potential yield, the rates of uranium reduction were nearly equivalent for all treatments (0.55-0.95 micromol L(-1) d(-1)). Uranium reduction with methanol proceeded after a 15-d longer lag time relative to that of ethanol or glucose. Significant differences were not found with the inclusion of humic acids. The extent of U reduction in sediment slurries measured by XANES at various time periods after the start of the experiment increased in the order of ethanol (5-7% reduced at 77 and 153 d), glucose (49% reduced at 53 d), and methanol (93% reduced at 90 d). The microbial diversity of ethanol- and methanol-amended microcosms in their late stage of U reduction was analyzed with 16S rRNA gene amplification. Members of the Geobacteraceae were found in all microcosms as well as other potential uranium-reducing organisms, such as Clostridium and Desulfosporosinus. The effectiveness of methanol relative to ethanol at reducing aqueous and sediment-hosted uranium suggests that bioremediation strategies that encourage fermentative poising of the subsurface to a lower redox potential may be more effective for long-term uranium immobilization as compared with selecting an electron donor that is efficiently metabolized by known uranium-reducing microorganisms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2134/jeq2008.0071DOI Listing
March 2009

Effect of low temperature and culture media on the growth and freeze-thawing tolerance of Exiguobacterium strains.

Cryobiology 2007 Apr 6;54(2):234-40. Epub 2007 Feb 6.

Department of Food Science, North Carolina State University, Raleigh, NC, USA.

Bacteria of the genus Exiguobacterium have been repeatedly isolated from ancient permafrost sediments of the Kolyma lowland of Northeast Eurasia. Here we report that the Siberian permafrost isolates Exiguobacterium sibiricum 255-15, E. sibiricum 7-3, Exiguobacterium undae 190-11 and E. sp. 5138, as well as Exiguobacterium antarcticum DSM 14480, isolated from a microbial mat sample of Lake Fryxell (McMurdo Dry Valleys, Antarctica), were able to grow at temperatures ranging from -6 to 40 degrees C. In comparison to cells grown at 24 degrees C, the cold-grown cells of these strains tended to be longer and wider. We also investigated the effect of growth conditions (broth or surface growth, and temperature) on cryotolerance of the Exiguobacterium strains. Bacteria grown in broth at 4 degrees C showed markedly greater survival following freeze-thawing treatments (20 repeated cycles) than bacteria grown in broth at 24 degrees C. Surprisingly, significant protection to repeated freeze-thawing was also observed when bacteria were grown on agar at either 4 or 24 degrees C.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cryobiol.2007.01.008DOI Listing
April 2007

Bacterial community in ancient Siberian permafrost as characterized by culture and culture-independent methods.

Astrobiology 2006 Jun;6(3):400-14

Center for Microbial Ecology, Michigan State University, East Lansing, Michigan, USA.

The microbial composition of ancient permafrost sediments from the Kolyma lowland of Northeast Eurasia was examined through culture and culture-independent approaches. These sediments have been continuously frozen for 5,000 to 2-3 million years. A total of 265 Bacteria 16S rRNA gene sequences were amplified from the permafrost total-community genomic DNA and screened by amplified ribosomal 16S rRNA restriction analysis. Members of three major lineages were found: gamma-Proteobacteria (mostly Xanthomonadaceae), Actinobacteria, and Firmicutes. We also determined partial 16S rRNA gene sequences of 49 isolates from a collection of 462 aerobes isolated from these sediments. The bacteria included Actinomycetales (Arthrobacter and Microbacteriaceae); followed by the Firmicutes (Exiguobacterium and Planomicrobium); the Bacteroidetes (Flavobacterium); the gamma-Proteobacteria (Psychrobacter); and the alpha-Proteobacteria (Sphingomonas). Both culture and culture-independent approaches showed the presence of high and low G+C Gram-positive bacteria and gamma-Proteobacteria. Some of the 16S rRNA gene sequences of environmental clones matched those of Arthrobacter isolates. Two-thirds of the isolates grew at -2.5 degrees C, indicating that they are psychroactive, and all are closely related to phylogenetic groups with strains from other cold environments, mostly commonly from Antarctica. The culturable and non-culturable microorganisms found in the terrestrial permafrost provide a prototype for possible life on the cryogenic planets of the Solar System.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/ast.2006.6.400DOI Listing
June 2006

Putative transposases conserved in Exiguobacterium isolates from ancient Siberian permafrost and from contemporary surface habitats.

Appl Environ Microbiol 2005 Nov;71(11):6954-62

NASA Astrobiology Institute, North Carolina State University, Schaub Hall, Room 339, Raleigh, NC 27695, USA.

Gram-positive bacteria of the genus Exiguobacterium have been repeatedly isolated from Siberian permafrost ranging in age from 20,000 to 2 to 3 million years and have been sporadically recovered from markedly diverse habitats, including microbial mats in Lake Fryxell (Antarctic), surface water, and food-processing environments. However, there is currently no information on genomic diversity of this microorganism or on the physiological strategies that have allowed its survival under prolonged freezing in the permafrost. Analysis of the genome sequence of the most ancient available Exiguobacterium isolate (Exiguobacterium sp. strain 255-15, from 2 to 3 million-year-old Siberian permafrost) revealed numerous putative transposase sequences, primarily of the IS200/IS605, IS30, and IS3 families, with four transposase families identified. Several of the transposase genes appeared to be part of insertion sequences. Southern blots with different transposase probes yielded high-resolution genomic fingerprints which differentiated the different permafrost isolates from each other and from the Exiguobacterium spp. type strains which have been derived from diverse surface habitats. Each of the Exiguobacterium sp. strain 255-15 transposases that were used as probes had highly conserved homologs in the genome of other Exiguobacterium strains, both from permafrost and from modern sites. These findings suggest that, prior to their entrapment in permafrost, Exiguobacterium isolates had acquired transposases and that conserved transposases are present in Exiguobacterium spp., which now can be isolated from various modern surface habitats.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/AEM.71.11.6954-6962.2005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1287632PMC
November 2005
-->