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Frolov EN, Gavrilov SN, Toshchakov SV, Zavarzina DG. Genomic Insights into Syntrophic Lifestyle of ' Candidatus Contubernalis alkaliaceticus' Based on the Reversed Wood-Ljungdahl Pathway and Mechanism of Direct Electron Transfer. Life (Basel) 2023; 13:2084. [PMID: 37895465 PMCID: PMC10608574 DOI: 10.3390/life13102084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 10/17/2023] [Accepted: 10/18/2023] [Indexed: 10/29/2023] Open
Abstract
The anaerobic oxidation of fatty acids and alcohols occurs near the thermodynamic limit of life. This process is driven by syntrophic bacteria that oxidize fatty acids and/or alcohols, their syntrophic partners that consume the products of this oxidation, and the pathways for interspecies electron exchange via these products or direct interspecies electron transfer (DIET). Due to the interdependence of syntrophic microorganisms on each other's metabolic activity, their isolation in pure cultures is almost impossible. Thus, little is known about their physiology, and the only available way to fill in the knowledge gap on these organisms is genomic and metabolic analysis of syntrophic cultures. Here we report the results of genome sequencing and analysis of an obligately syntrophic alkaliphilic bacterium 'Candidatus Contubernalis alkaliaceticus'. The genomic data suggest that acetate oxidation is carried out by the Wood-Ljungdahl pathway, while a bimodular respiratory system involving an Rnf complex and a Na+-dependent ATP synthase is used for energy conservation. The predicted genomic ability of 'Ca. C. alkaliaceticus' to outperform interspecies electron transfer both indirectly, via H2 or formate, and directly, via pili-like appendages of its syntrophic partner or conductive mineral particles, was experimentally demonstrated. This is the first indication of DIET in the class Dethiobacteria.
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Affiliation(s)
- Evgenii N. Frolov
- Winogradsky Institute of Microbiology, Federal Research Center of Biotechnology of the Russian Academy of Sciences, 60 Let Oktjabrja Pr-t, 7, Bld. 2, Moscow 117312, Russia; (S.N.G.); (D.G.Z.)
| | - Sergey N. Gavrilov
- Winogradsky Institute of Microbiology, Federal Research Center of Biotechnology of the Russian Academy of Sciences, 60 Let Oktjabrja Pr-t, 7, Bld. 2, Moscow 117312, Russia; (S.N.G.); (D.G.Z.)
| | - Stepan V. Toshchakov
- National Research Centre “Kurchatov Institute”, Akademika Kurchatova Sq., 1, Moscow 123182, Russia;
| | - Daria G. Zavarzina
- Winogradsky Institute of Microbiology, Federal Research Center of Biotechnology of the Russian Academy of Sciences, 60 Let Oktjabrja Pr-t, 7, Bld. 2, Moscow 117312, Russia; (S.N.G.); (D.G.Z.)
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Khomyakova MA, Merkel AY, Slobodkin AI, Sorokin DY. Phenotypic and genomic characterization of the first alkaliphilic aceticlastic methanogens and proposal of a novel genus Methanocrinis gen.nov. within the family Methanotrichaceae. Front Microbiol 2023; 14:1233691. [PMID: 37886072 PMCID: PMC10598746 DOI: 10.3389/fmicb.2023.1233691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 09/12/2023] [Indexed: 10/28/2023] Open
Abstract
Highly purified cultures of alkaliphilic aceticlastic methanogens were collected for the first time using methanogenic enrichments with acetate from a soda lake and a terrestrial mud volcano. The cells of two strains were non-motile rods forming filaments. The mud volcano strain M04Ac was alkalitolerant, with the pH range for growth from 7.5 to 10.0 (optimum at 9.0), while the soda lake strain Mx was an obligate alkaliphile growing in the pH range 7.7-10.2 (optimum 9.3-9.5) in the presence of optimally 0.2-0.3 M total Na+. Genomes of both strains encoded all enzymes required for aceticlastic methanogenesis and different mechanisms of (halo)alkaline adaptations, including ectoine biosynthesis, which is the first evidence for the formation of this osmoprotectant in archaea. According to 16S rRNA gene phylogeny, the strains possessed 98.3-98.9% sequence identity and belonged to the obligately aceticlastic genus Methanothrix with M. harundinaceae as the most closely related species. However, a more advanced phylogenomic reconstruction based on 122 conserved single-copy archaeal protein-coding marker genes clearly indicated a polyphyletic origin of the species included in the genus Methanothrix. We propose to reclassify Methanothrix harrundinacea (type strain 8AcT) into a new genus, Methanocrinis gen. nov., with the type species Methanocrinis harrundinaceus comb. nov. We also propose under SeqCode the complete genome sequences of strain MxTs (GCA_029167045.1) and strain M04AcTs (GCA_029167205.1) as nomenclatural types of Methanocrinis natronophilus sp. nov. and Methanocrinis alkalitolerans sp. nov., respectively, which represent other species of the novel genus. This work demonstrates that the low energy aceticlastic methanogenesis may function at extreme conditions present in (halo)alkaline habitats.
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Affiliation(s)
- Maria A. Khomyakova
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Moscow, Russia
| | - Alexander Y. Merkel
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Moscow, Russia
| | - Alexander I. Slobodkin
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Moscow, Russia
| | - Dimitry Y. Sorokin
- Winogradsky Institute of Microbiology, FRC Biotechnology Russian Academy of Sciences, Moscow, Russia
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands
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Zavarzina DG, Merkel AY, Klyukina AA, Elizarov IM, Pikhtereva VA, Rusakov VS, Chistyakova NI, Ziganshin RH, Maslov AA, Gavrilov SN. Iron or sulfur respiration-an adaptive choice determining the fitness of a natronophilic bacterium Dethiobacter alkaliphilus in geochemically contrasting environments. Front Microbiol 2023; 14:1108245. [PMID: 37520367 PMCID: PMC10376724 DOI: 10.3389/fmicb.2023.1108245] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 06/26/2023] [Indexed: 08/01/2023] Open
Abstract
Haloalkaliphilic microorganisms are double extremophiles functioning optimally at high salinity and pH. Their typical habitats are soda lakes, geologically ancient yet widespread ecosystems supposed to harbor relict microbial communities. We compared metabolic features and their determinants in two strains of the natronophilic species Dethiobacter alkaliphilus, the only cultured representative of the class "Dethiobacteria" (Bacillota). The strains of D. alkaliphilus were previously isolated from geographically remote Mongolian and Kenyan soda lakes. The type strain AHT1T was described as a facultative chemolithoautotrophic sulfidogen reducing or disproportionating sulfur or thiosulfate, while strain Z-1002 was isolated as a chemolithoautotrophic iron reducer. Here, we uncovered the iron reducing ability of strain AHT1T and the ability of strain Z-1002 for thiosulfate reduction and anaerobic Fe(II) oxidation. Key catabolic processes sustaining the growth of both D. alkaliphilus strains appeared to fit the geochemical settings of two contrasting natural alkaline environments, sulfur-enriched soda lakes and iron-enriched serpentinites. This hypothesis was supported by a meta-analysis of Dethiobacterial genomes and by the enrichment of a novel phylotype from a subsurface alkaline aquifer under Fe(III)-reducing conditions. Genome analysis revealed multiheme c-type cytochromes to be the most probable determinants of iron and sulfur redox transformations in D. alkaliphilus. Phylogeny reconstruction showed that all the respiratory processes in this organism are likely provided by evolutionarily related early forms of unconventional octaheme tetrathionate and sulfite reductases and their structural analogs, OmhA/OcwA Fe(III)-reductases. Several phylogenetically related determinants of anaerobic Fe(II) oxidation were identified in the Z-1002 genome, and the oxidation process was experimentally demonstrated. Proteomic profiling revealed two distinct sets of multiheme cytochromes upregulated in iron(III)- or thiosulfate-respiring cells and the cytochromes peculiar for Fe(II) oxidizing cells. We suggest that maintaining high variation in multiheme cytochromes is an effective adaptive strategy to occupy geochemically contrasting alkaline environments. We propose that sulfur-enriched soda lakes could be secondary habitats for D. alkaliphilus compared to Fe-rich serpentinites, and that the ongoing evolution of Dethiobacterales could retrace the evolutionary path that may have occurred in prokaryotes at a turning point in the biosphere's history, when the intensification of the sulfur cycle outweighed the global significance of the iron cycle.
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Affiliation(s)
- Daria G. Zavarzina
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Alexander Yu Merkel
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Alexandra A. Klyukina
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Ivan M. Elizarov
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Valeria A. Pikhtereva
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | | | | | - Rustam H. Ziganshin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
| | - Alexey A. Maslov
- Faculty of Geology, Lomonosov Moscow State University, Moscow, Russia
| | - Sergey N. Gavrilov
- Winogradsky Institute of Microbiology, FRC Biotechnology, Russian Academy of Sciences, Moscow, Russia
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Song W, Xiong H, Qi R, Wang S, Yang Y. Effect of salinity and algae biomass on mercury cycling genes and bacterial communities in sediments under mercury contamination: Implications of the mercury cycle in arid regions. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 269:116141. [PMID: 33290948 DOI: 10.1016/j.envpol.2020.116141] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/22/2020] [Accepted: 11/19/2020] [Indexed: 06/12/2023]
Abstract
Lakes in arid regions are experiencing mercury pollution via air deposition and surface runoff, posing a threat to ecosystem safety and human health. Furthermore, salinity and organic matter input could influence the mercury cycle and composition of bacterial communities in the sediment. In this study, the effects of salinity and algae biomass as an important organic matter on the genes (merA and hgcA) involved in the mercury cycle under mercury contamination were investigated. Archaeal merA and hgcA were not detected in sediments of lake microcosms, indicating that bacteria rather than archaea played a crucial role in mercury reduction and methylation. The high content of mercury (300 ng g-1) could reduce the abundance of both merA and hgcA. The effects of salinity and algae biomass on mercury cycling genes depended on the gene type and dose. A higher input of algae biomass (250 mg L-1) led to an increase of merA abundance, but a decrease of hgcA abundance. All high inputs of mercury, salinity, and algae biomass decreased the richness and diversity of bacterial communities in sediment. Further analysis indicated that higher mercury (300 ng g-1) led to an increased relative abundance of mercury methylators, such as Ruminococcaceae, Bacteroidaceae, and Veillonellaceae. Under saline conditions (10 and 30 g L-1), the richness of specific bacteria associated with mercury reduction (Halomonadaceae) and methylation (Syntrophomonadaceae) increased compared to the control. The input of algae biomass led to an increase in the specific bacterial communities associated with the mercury cycle and the richness of bacteria involved in the decomposition of organic matter. These results provide insight into mercury cycle-related genes and bacterial communities in the sediments of lakes in arid regions.
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Affiliation(s)
- Wenjuan Song
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Heigang Xiong
- College of Applied Arts and Science of Beijing Union University, Beijing, 100191, China
| | - Ran Qi
- Command Center of Comprehensive Natural Resources Survey, China Geological Survey, Beijing, 100055, China; Institute of Geological Survey, China University of Geosciences, Wuhan, 430074, China
| | - Shuzhi Wang
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, 830011, China
| | - Yuyi Yang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, 430074, China
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Oren A, Garrity GM, Parker CT, Chuvochina M, Trujillo ME. Lists of names of prokaryotic Candidatus taxa. Int J Syst Evol Microbiol 2020; 70:3956-4042. [DOI: 10.1099/ijsem.0.003789] [Citation(s) in RCA: 782] [Impact Index Per Article: 156.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We here present annotated lists of names of Candidatus taxa of prokaryotes with ranks between subspecies and class, proposed between the mid-1990s, when the provisional status of Candidatus taxa was first established, and the end of 2018. Where necessary, corrected names are proposed that comply with the current provisions of the International Code of Nomenclature of Prokaryotes and its Orthography appendix. These lists, as well as updated lists of newly published names of Candidatus taxa with additions and corrections to the current lists to be published periodically in the International Journal of Systematic and Evolutionary Microbiology, may serve as the basis for the valid publication of the Candidatus names if and when the current proposals to expand the type material for naming of prokaryotes to also include gene sequences of yet-uncultivated taxa is accepted by the International Committee on Systematics of Prokaryotes.
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Affiliation(s)
- Aharon Oren
- The Institute of Life Sciences, The Hebrew University of Jerusalem, The Edmond J. Safra Campus, 9190401 Jerusalem, Israel
| | - George M. Garrity
- NamesforLife, LLC, PO Box 769, Okemos MI 48805-0769, USA
- Department of Microbiology & Molecular Genetics, Biomedical Physical Sciences, Michigan State University, East Lansing, MI 48824-4320, USA
| | | | - Maria Chuvochina
- Australian Centre for Ecogenomics, University of Queensland, St. Lucia QLD 4072, Brisbane, Australia
| | - Martha E. Trujillo
- Departamento de Microbiología y Genética, Campus Miguel de Unamuno, Universidad de Salamanca, 37007, Salamanca, Spain
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Complete Genome Sequence of " Candidatus Syntrophocurvum alkaliphilum" Strain B(2M), Obtained from the Metagenome of a Salt-Tolerant Alkaliphilic Anaerobic Syntrophic Butyrate-Degrading Consortium. Microbiol Resour Announc 2020; 9:9/6/e01511-19. [PMID: 32029557 PMCID: PMC7005122 DOI: 10.1128/mra.01511-19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A highly salt-tolerant and alkaliphilic syntrophic consortium that degrades butyrate under sulfate-reducing conditions was purified from a hypersaline soda lake in southwest Siberia. Here, we present the complete genome sequence of the syntrophic primary butyrate degrader in order to understand the molecular mechanisms of interaction between consortium members.
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Feng J, Shentu J, Zhu Y, Tang C, He Y, Xu J. Crop-dependent root-microbe-soil interactions induce contrasting natural attenuation of organochlorine lindane in soils. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 257:113580. [PMID: 31753626 DOI: 10.1016/j.envpol.2019.113580] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 09/19/2019] [Accepted: 11/04/2019] [Indexed: 06/10/2023]
Abstract
Plant-specific root-microbe-soil interactions play an indisputable role in microbial adaptation to environmental stresses. However, the assembly of plant rhizosphere microbiomes and their feedbacks in modification of pollution alleviation under organochlorine stress condition is far less clear. This study examined the response of root-associated bacterial microbiomes to lindane pollution and compared the dissipation of lindane in maize-cultivated dry soils and rice-cultivated flooded soils. Results showed that lindane pollution dramatically altered the microbial structure in the rhizosphere soil of maize but had less influence on the microbial composition in flooded treatments regardless of rice growth, when the reductive dechlorination of lindane was actively coupled with natural redox processes under anaerobic conditions. After 30 days of plant growth, lindane residues dissipated much faster in anaerobic than in aerobic environments, with only 1.08 mg kg-1 lindane remaining in flooded control compared to 12.79 mg kg-1 in dry control soils. Compared to the corresponding unplanted control, maize growth significantly increased, but rice growth slightly decreased the dissipation of lindane. Our study suggests that opposite impacts would lead to the self-purification of polluted soils during the growth of xerophytic maize and hygrocolous rice. This was attributed to the contrasting belowground micro-ecological processes regarding protection of root tissues and thereby assembly of rhizosphere microbiomes shaped by the xerophytic and hygrocolous crops under different water managements, in response to lindane pollution.
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Affiliation(s)
- Jiayin Feng
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China
| | - Jue Shentu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China
| | - Yanjie Zhu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China
| | - Caixian Tang
- Department of Animal, Plant and Soil Sciences, Centre for AgriBioscience, La Trobe University, Melbourne Campus, Bundoora, VIC 3086, Australia
| | - Yan He
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China.
| | - Jianming Xu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China
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Syntrophic growth of alkaliphilic anaerobes controlled by ferric and ferrous minerals transformation coupled to acetogenesis. ISME JOURNAL 2019; 14:425-436. [PMID: 31641279 DOI: 10.1038/s41396-019-0527-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 08/02/2019] [Accepted: 09/14/2019] [Indexed: 12/26/2022]
Abstract
Redox-active iron minerals can act as energy sources or electron-transferring mediators in microbial syntrophic associations, being important means of interspecies metabolic cooperation in sedimentary environments. Alkaline conditions alter the thermodynamic stability of iron minerals, influencing their availability for interspecies syntrophic interactions. We have modeled anaerobic alkaliphilic microbial associations in ethanol-oxidizing co-culture of an obligate syntroph Candidatus "Contubernalis alkalaceticum" and a facultative lithotroph Geoalkalibacter ferrihydriticus, which is capable of dissimilatory Fe(III) reduction and homoacetogenic oxidation of Fe(II) with CO2. The co-cultures were cultivated with thermodynamically metastable ferric-containing ferrihydrite, or ferrous-containing siderite, or without minerals. Mössbauer spectral analysis revealed the transformation of both minerals to the stable magnetite. In the presence of ferrihydrite, G. ferrihydriticus firstly reduced Fe(III) with ethanol and then switched to syntrophic homoacetogenesis, providing the growth of obligate syntroph on ethanol. The ability of G. ferrihydriticus to accept hydrogen from its syntrophic partner and produce extra acetate from carbonate during ethanol oxidation was confirmed by co-culture growth without minerals. In the presence of siderite, G. ferrihydriticus performed homoacetogenesis using two electron donors simultaneously- siderite and hydrogen. Pieces of evidence for direct and indirect hydrogen-mediated electron exchange between partner organisms were obtained. Relative abundancies of partner organisms and the rate of acetate production by their co-cultures were strongly determined by thermodynamic benefits, which G. ferrihydriticus got from redox transformations of iron minerals. Even the minor growth of G. ferrihydriticus sustained the growth of the syntroph. Accordingly, microbe-to-mineral interactions could represent underestimated drivers of syntrophic interactions in alkaline sedimentary environments.
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Timmers PHA, Vavourakis CD, Kleerebezem R, Damsté JSS, Muyzer G, Stams AJM, Sorokin DY, Plugge CM. Metabolism and Occurrence of Methanogenic and Sulfate-Reducing Syntrophic Acetate Oxidizing Communities in Haloalkaline Environments. Front Microbiol 2018; 9:3039. [PMID: 30619130 PMCID: PMC6295475 DOI: 10.3389/fmicb.2018.03039] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 11/26/2018] [Indexed: 01/31/2023] Open
Abstract
Anaerobic syntrophic acetate oxidation (SAO) is a thermodynamically unfavorable process involving a syntrophic acetate oxidizing bacterium (SAOB) that forms interspecies electron carriers (IECs). These IECs are consumed by syntrophic partners, typically hydrogenotrophic methanogenic archaea or sulfate reducing bacteria. In this work, the metabolism and occurrence of SAOB at extremely haloalkaline conditions were investigated, using highly enriched methanogenic (M-SAO) and sulfate-reducing (S-SAO) cultures from south-western Siberian hypersaline soda lakes. Activity tests with the M-SAO and S-SAO cultures and thermodynamic calculations indicated that H2 and formate are important IECs in both SAO cultures. Metagenomic analysis of the M-SAO cultures showed that the dominant SAOB was ‘Candidatus Syntrophonatronum acetioxidans,’ and a near-complete draft genome of this SAOB was reconstructed. ‘Ca. S. acetioxidans’ has all genes necessary for operating the Wood–Ljungdahl pathway, which is likely employed for acetate oxidation. It also encodes several genes essential to thrive at haloalkaline conditions; including a Na+-dependent ATP synthase and marker genes for ‘salt-out‘ strategies for osmotic homeostasis at high soda conditions. Membrane lipid analysis of the M-SAO culture showed the presence of unusual bacterial diether membrane lipids which are presumably beneficial at extreme haloalkaline conditions. To determine the importance of SAO in haloalkaline environments, previously obtained 16S rRNA gene sequencing data and metagenomic data of five different hypersaline soda lake sediment samples were investigated, including the soda lakes where the enrichment cultures originated from. The draft genome of ‘Ca. S. acetioxidans’ showed highest identity with two metagenome-assembled genomes (MAGs) of putative SAOBs that belonged to the highly abundant and diverse Syntrophomonadaceae family present in the soda lake sediments. The 16S rRNA gene amplicon datasets of the soda lake sediments showed a high similarity of reads to ‘Ca. S. acetioxidans’ with abundance as high as 1.3% of all reads, whereas aceticlastic methanogens and acetate oxidizing sulfate-reducers were not abundant (≤0.1%) or could not be detected. These combined results indicate that SAO is the primary anaerobic acetate oxidizing pathway at extreme haloalkaline conditions performed by haloalkaliphilic syntrophic consortia.
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Affiliation(s)
- Peer H A Timmers
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands.,European Centre of Excellence for Sustainable Water Technology, Wetsus, Leeuwarden, Netherlands
| | - Charlotte D Vavourakis
- Microbial Systems Ecology, Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands
| | - Robbert Kleerebezem
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Jaap S Sinninghe Damsté
- Department of Marine Microbiology and Biogeochemistry, NIOZ Netherlands Institute for Sea Research, Utrecht University, Utrecht, Netherlands.,Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Gerard Muyzer
- Microbial Systems Ecology, Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, Netherlands
| | - Alfons J M Stams
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands.,Centre of Biological Engineering, University of Minho, Braga, Portugal
| | - Dimity Y Sorokin
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands.,Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Caroline M Plugge
- Laboratory of Microbiology, Wageningen University & Research, Wageningen, Netherlands.,European Centre of Excellence for Sustainable Water Technology, Wetsus, Leeuwarden, Netherlands
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Vavourakis CD, Andrei AS, Mehrshad M, Ghai R, Sorokin DY, Muyzer G. A metagenomics roadmap to the uncultured genome diversity in hypersaline soda lake sediments. MICROBIOME 2018; 6:168. [PMID: 30231921 PMCID: PMC6146748 DOI: 10.1186/s40168-018-0548-7] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Accepted: 09/03/2018] [Indexed: 05/06/2023]
Abstract
BACKGROUND Hypersaline soda lakes are characterized by extreme high soluble carbonate alkalinity. Despite the high pH and salt content, highly diverse microbial communities are known to be present in soda lake brines but the microbiome of soda lake sediments received much less attention of microbiologists. Here, we performed metagenomic sequencing on soda lake sediments to give the first extensive overview of the taxonomic diversity found in these complex, extreme environments and to gain novel physiological insights into the most abundant, uncultured prokaryote lineages. RESULTS We sequenced five metagenomes obtained from four surface sediments of Siberian soda lakes with a pH 10 and a salt content between 70 and 400 g L-1. The recovered 16S rRNA gene sequences were mostly from Bacteria, even in the salt-saturated lakes. Most OTUs were assigned to uncultured families. We reconstructed 871 metagenome-assembled genomes (MAGs) spanning more than 45 phyla and discovered the first extremophilic members of the Candidate Phyla Radiation (CPR). Five new species of CPR were among the most dominant community members. Novel dominant lineages were found within previously well-characterized functional groups involved in carbon, sulfur, and nitrogen cycling. Moreover, key enzymes of the Wood-Ljungdahl pathway were encoded within at least four bacterial phyla never previously associated with this ancient anaerobic pathway for carbon fixation and dissimilation, including the Actinobacteria. CONCLUSIONS Our first sequencing effort of hypersaline soda lake sediment metagenomes led to two important advances. First, we showed the existence and obtained the first genomes of haloalkaliphilic members of the CPR and several hundred other novel prokaryote lineages. The soda lake CPR is a functionally diverse group, but the most abundant organisms in this study are likely fermenters with a possible role in primary carbon degradation. Second, we found evidence for the presence of the Wood-Ljungdahl pathway in many more taxonomic groups than those encompassing known homo-acetogens, sulfate-reducers, and methanogens. Since only few environmental metagenomics studies have targeted sediment microbial communities and never to this extent, we expect that our findings are relevant not only for the understanding of haloalkaline environments but can also be used to set targets for future studies on marine and freshwater sediments.
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Affiliation(s)
- Charlotte D. Vavourakis
- Microbial Systems Ecology, Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, Faculty of Science, University of Amsterdam, Postbus 94248, 1090 GE Amsterdam, the Netherlands
| | - Adrian-Stefan Andrei
- Department of Aquatic Microbial Ecology, Institute of Hydrobiology, Biology Centre CAS, Na Sadkach 7, 370 05 Ceske Budejovice, Czech Republic
| | - Maliheh Mehrshad
- Department of Aquatic Microbial Ecology, Institute of Hydrobiology, Biology Centre CAS, Na Sadkach 7, 370 05 Ceske Budejovice, Czech Republic
| | - Rohit Ghai
- Department of Aquatic Microbial Ecology, Institute of Hydrobiology, Biology Centre CAS, Na Sadkach 7, 370 05 Ceske Budejovice, Czech Republic
| | - Dimitry Y. Sorokin
- Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences, 60 let Oktyabrya pr-t, 7, bld. 2, Moscow, Russian Federation 117312
- Environmental Biotechnology, Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Gerard Muyzer
- Microbial Systems Ecology, Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, Faculty of Science, University of Amsterdam, Postbus 94248, 1090 GE Amsterdam, the Netherlands
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Effect of salinity on diazotrophic activity and microbial composition of phototrophic communities from Bitter-1 soda lake (Kulunda Steppe, Russia). Extremophiles 2018; 22:651-663. [DOI: 10.1007/s00792-018-1026-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 04/06/2018] [Indexed: 11/25/2022]
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12
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Sorokin DY, Chernyh NA. Desulfonatronospira sulfatiphila sp. nov., and Desulfitispora elongata sp. nov., two novel haloalkaliphilic sulfidogenic bacteria from soda lakes. Int J Syst Evol Microbiol 2017; 67:396-401. [DOI: 10.1099/ijsem.0.001640] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Dimitry Y. Sorokin
- Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences, Leninskii Avenue 33/2, Moscow 119071, Russia
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Nikolai A. Chernyh
- Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences, Leninskii Avenue 33/2, Moscow 119071, Russia
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13
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Gudelj I, Kinnersley M, Rashkov P, Schmidt K, Rosenzweig F. Stability of Cross-Feeding Polymorphisms in Microbial Communities. PLoS Comput Biol 2016; 12:e1005269. [PMID: 28036324 PMCID: PMC5201250 DOI: 10.1371/journal.pcbi.1005269] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 11/28/2016] [Indexed: 11/18/2022] Open
Abstract
Cross-feeding, a relationship wherein one organism consumes metabolites excreted by another, is a ubiquitous feature of natural and clinically-relevant microbial communities and could be a key factor promoting diversity in extreme and/or nutrient-poor environments. However, it remains unclear how readily cross-feeding interactions form, and therefore our ability to predict their emergence is limited. In this paper we developed a mathematical model parameterized using data from the biochemistry and ecology of an E. coli cross-feeding laboratory system. The model accurately captures short-term dynamics of the two competitors that have been observed empirically and we use it to systematically explore the stability of cross-feeding interactions for a range of environmental conditions. We find that our simple system can display complex dynamics including multi-stable behavior separated by a critical point. Therefore whether cross-feeding interactions form depends on the complex interplay between density and frequency of the competitors as well as on the concentration of resources in the environment. Moreover, we find that subtly different environmental conditions can lead to dramatically different results regarding the establishment of cross-feeding, which could explain the apparently unpredictable between-population differences in experimental outcomes. We argue that mathematical models are essential tools for disentangling the complexities of cross-feeding interactions.
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Affiliation(s)
- Ivana Gudelj
- Biosciences, University of Exeter, Exeter, United Kingdom
- * E-mail:
| | - Margie Kinnersley
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
| | - Peter Rashkov
- Biosciences, University of Exeter, Exeter, United Kingdom
| | - Karen Schmidt
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
| | - Frank Rosenzweig
- Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, United States of America
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'Candidatus Desulfonatronobulbus propionicus': a first haloalkaliphilic member of the order Syntrophobacterales from soda lakes. Extremophiles 2016; 20:895-901. [PMID: 27734192 DOI: 10.1007/s00792-016-0881-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 10/04/2016] [Indexed: 10/20/2022]
Abstract
Propionate can be directly oxidized anaerobically with sulfate as e-acceptor at haloalkaline conditions either incompletely to acetate (an example is Desulfobulbus alkaliphilus), or completely (for example by the members of genus Desulfonatronobacter). An enrichment with propionate at methanogenic conditions (without sulfate) inoculated with mixed sediments from hypersaline soda lakes in Kulunda Steppe (Altai, Russia) resulted in a domination of a new member of Syntrophobacteraceae (Deltaproteobacteria) in a consortium with the haloalkaliphilic lithotrophic methanogen Methanocalculus alkaliphilus. Transfer of this culture to a medium containing propionate as e-donor and sulfate as e-acceptor resulted in a disappearance of the methanogen and sulfide formation by the bacterial component, finally isolated into a pure culture at these conditions. Strain APr1 formed a distinct phylogenetic lineage within the family Syntrophobacteraceae, being equally distant from its members at the genus level. Phenotypically, strain APr1 resembled the species of the genus Syntrophobacter with substrate spectrum restricted to propionate and propanol utilized with sulfate, sulfite and thiosulfate as the e-acceptors. Propionate is oxidized incompletely to acetate. It is a moderately salt-tolerant (max. 1.2 M Na+) obligate alkaliphile (pH opt. 10). The isolate is proposed to be classified as a new candidate genus and species 'Candidatus Desulfonatronobulbus propionicus'.
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15
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Sorokin DY, Abbas B, Geleijnse M, Kolganova TV, Kleerebezem R, van Loosdrecht MCM. Syntrophic associations from hypersaline soda lakes converting organic acids and alcohols to methane at extremely haloalkaline conditions. Environ Microbiol 2016; 18:3189-202. [DOI: 10.1111/1462-2920.13448] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Dimitry Y. Sorokin
- Winogradsky Institute of Microbiology, Research Centre of Biotechnology, Russian Academy of Sciences; Moscow Russia
- Department of Biotechnology; Delft University of Technology; 2628 Delft BC The Netherlands
| | - Ben Abbas
- Department of Biotechnology; Delft University of Technology; 2628 Delft BC The Netherlands
| | - Mitchell Geleijnse
- Department of Biotechnology; Delft University of Technology; 2628 Delft BC The Netherlands
| | - Tatjana V. Kolganova
- Centre Bioengineering; Research Centre of Biotechnology, Russian Academy of Sciences; Moscow Russia
| | - Robbert Kleerebezem
- Department of Biotechnology; Delft University of Technology; 2628 Delft BC The Netherlands
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16
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A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes. Adv Microb Physiol 2015. [PMID: 26210106 DOI: 10.1016/bs.ampbs.2015.05.002] [Citation(s) in RCA: 189] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Dissimilatory sulphate reduction is the unifying and defining trait of sulphate-reducing prokaryotes (SRP). In their predominant habitats, sulphate-rich marine sediments, SRP have long been recognized to be major players in the carbon and sulphur cycles. Other, more recently appreciated, ecophysiological roles include activity in the deep biosphere, symbiotic relations, syntrophic associations, human microbiome/health and long-distance electron transfer. SRP include a high diversity of organisms, with large nutritional versatility and broad metabolic capacities, including anaerobic degradation of aromatic compounds and hydrocarbons. Elucidation of novel catabolic capacities as well as progress in the understanding of metabolic and regulatory networks, energy metabolism, evolutionary processes and adaptation to changing environmental conditions has greatly benefited from genomics, functional OMICS approaches and advances in genetic accessibility and biochemical studies. Important biotechnological roles of SRP range from (i) wastewater and off gas treatment, (ii) bioremediation of metals and hydrocarbons and (iii) bioelectrochemistry, to undesired impacts such as (iv) souring in oil reservoirs and other environments, and (v) corrosion of iron and concrete. Here we review recent advances in our understanding of SRPs focusing mainly on works published after 2000. The wealth of publications in this period, covering many diverse areas, is a testimony to the large environmental, biogeochemical and technological relevance of these organisms and how much the field has progressed in these years, although many important questions and applications remain to be explored.
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Sorokin DY, Chernyh NA, Poroshina MN. Desulfonatronobacter acetoxydans sp. nov.,: a first acetate-oxidizing, extremely salt-tolerant alkaliphilic SRB from a hypersaline soda lake. Extremophiles 2015; 19:899-907. [PMID: 26085472 PMCID: PMC4546703 DOI: 10.1007/s00792-015-0765-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 05/26/2015] [Indexed: 11/27/2022]
Abstract
Recent intensive microbiological investigation of sulfidogenesis in soda lakes did not result in isolation of any pure cultures of sulfate-reducing bacteria (SRB) able to directly oxidize acetate. The sulfate-dependent acetate oxidation at haloalkaline conditions has, so far, been only shown in two syntrophic associations of novel Syntrophobacteraceae members and haloalkaliphilic hydrogenotrophic SRB. In the course of investigation of one of them, obtained from a hypersaline soda lake in South-Western Siberia, a minor component was observed showing a close relation to Desulfonatronobacter acidivorans--a "complete oxidizing" SRB from soda lakes. This organism became dominant in a secondary enrichment with propionate as e-donor and sulfate as e-acceptor. A pure culture, strain APT3, was identified as a novel member of the family Desulfobacteraceae. It is an extremely salt-tolerant alkaliphile, growing with butyrate at salinity up to 4 M total Na(+) with a pH optimum at 9.5. It can grow with sulfate as e-acceptor with C3-C9 VFA and also with some alcohols. The most interesting property of strain APT3 is its ability to grow with acetate as e-donor, although not with sulfate, but with sulfite or thiosulfate as e-acceptors. The new isolate is proposed as a new species Desulfonatronobacter acetoxydans.
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Affiliation(s)
- D Y Sorokin
- Winogradsky Institute of Microbiology, Russian Academy of Sciences, Prospect 60-let Octyabrya 7/2, 117811, Moscow, Russia,
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Sorokin DY, Banciu HL, Muyzer G. Functional microbiology of soda lakes. Curr Opin Microbiol 2015; 25:88-96. [PMID: 26025021 DOI: 10.1016/j.mib.2015.05.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 04/30/2015] [Accepted: 05/01/2015] [Indexed: 10/23/2022]
Abstract
Soda lakes represent unique permanently haloalkaline system. Despite the harsh conditions, they are inhabited by abundant, mostly prokaryotic, microbial communities. This review summarizes results of studies of main functional groups of the soda lake prokaryotes responsible for carbon, nitrogen and sulfur cycling, including oxygenic and anoxygenic phototrophs, aerobic chemolithotrophs, fermenting and respiring anaerobes. The main conclusion from this work is that the soda lakes are very different from other high-salt systems in respect to microbial richness and activity. The reason for this difference is determined by the major physico-chemical features of two dominant salts - NaCl in neutral saline systems and sodium carbonates in soda lakes, that are influencing the amount of energy required for osmotic adaptation.
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Affiliation(s)
- Dimitry Y Sorokin
- Winogradsky Institute of Microbiology, Russian Academy of Sciences, Moscow, Russia; Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
| | - Horia L Banciu
- Institute for Interdisciplinary Research in Bio-Nano-Sciences, Babeş-Bolyai University, Cluj-Napoca, Romania; Department of Molecular Biology and Biotechnology, Faculty of Biology and Geology, Babeş-Bolyai University, Cluj-Napoca, Romania
| | - Gerard Muyzer
- Microbial Systems Ecology, Department of Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
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Tourova TP, Grechnikova MA, Kuznetsov BB, Sorokin DY. Phylogenetic diversity of bacteria in soda lake stratified sediments. Microbiology (Reading) 2014. [DOI: 10.1134/s0026261714060186] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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20
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Sorokin DY, Berben T, Melton ED, Overmars L, Vavourakis CD, Muyzer G. Microbial diversity and biogeochemical cycling in soda lakes. Extremophiles 2014; 18:791-809. [PMID: 25156418 PMCID: PMC4158274 DOI: 10.1007/s00792-014-0670-9] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 06/26/2014] [Indexed: 01/26/2023]
Abstract
Soda lakes contain high concentrations of sodium carbonates resulting in a stable elevated pH, which provide a unique habitat to a rich diversity of haloalkaliphilic bacteria and archaea. Both cultivation-dependent and -independent methods have aided the identification of key processes and genes in the microbially mediated carbon, nitrogen, and sulfur biogeochemical cycles in soda lakes. In order to survive in this extreme environment, haloalkaliphiles have developed various bioenergetic and structural adaptations to maintain pH homeostasis and intracellular osmotic pressure. The cultivation of a handful of strains has led to the isolation of a number of extremozymes, which allow the cell to perform enzymatic reactions at these extreme conditions. These enzymes potentially contribute to biotechnological applications. In addition, microbial species active in the sulfur cycle can be used for sulfur remediation purposes. Future research should combine both innovative culture methods and state-of-the-art 'meta-omic' techniques to gain a comprehensive understanding of the microbes that flourish in these extreme environments and the processes they mediate. Coupling the biogeochemical C, N, and S cycles and identifying where each process takes place on a spatial and temporal scale could unravel the interspecies relationships and thereby reveal more about the ecosystem dynamics of these enigmatic extreme environments.
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Affiliation(s)
- Dimitry Y. Sorokin
- Winogradsky Institute of Microbiology, RAS, Moscow, Russia
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
| | - Tom Berben
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
| | - Emily Denise Melton
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
| | - Lex Overmars
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
| | - Charlotte D. Vavourakis
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
| | - Gerard Muyzer
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands
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A genomic view on syntrophic versus non-syntrophic lifestyle in anaerobic fatty acid degrading communities. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:2004-2016. [PMID: 24973598 DOI: 10.1016/j.bbabio.2014.06.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 06/05/2014] [Accepted: 06/09/2014] [Indexed: 11/22/2022]
Abstract
In sulfate-reducing and methanogenic environments complex biopolymers are hydrolyzed and degraded by fermentative micro-organisms that produce hydrogen, carbon dioxide and short chain fatty acids. Degradation of short chain fatty acids can be coupled to methanogenesis or to sulfate-reduction. Here we study from a genome perspective why some of these micro-organisms are able to grow in syntrophy with methanogens and others are not. Bacterial strains were selected based on genome availability and upon their ability to grow on short chain fatty acids alone or in syntrophic association with methanogens. Systematic functional domain profiling allowed us to shed light on this fundamental and ecologically important question. Extra-cytoplasmic formate dehydrogenases (InterPro domain number; IPR006443), including their maturation protein FdhE (IPR024064 and IPR006452) is a typical difference between syntrophic and non-syntrophic butyrate and propionate degraders. Furthermore, two domains with a currently unknown function seem to be associated with the ability of syntrophic growth. One is putatively involved in capsule or biofilm production (IPR019079) and a second in cell division, shape-determination or sporulation (IPR018365). The sulfate-reducing bacteria Desulfobacterium autotrophicum HRM2, Desulfomonile tiedjei and Desulfosporosinus meridiei were never tested for syntrophic growth, but all crucial domains were found in their genomes, which suggests their possible ability to grow in syntrophic association with methanogens. In addition, profiling domains involved in electron transfer mechanisms revealed the important role of the Rnf-complex and the formate transporter in syntrophy, and indicate that DUF224 may have a role in electron transfer in bacteria other than Syntrophomonas wolfei as well. This article is a part of a Special Issue entitled: 18th European Bioenergetics Conference (Biochim. Biophys. Acta, Volume 1837, Issue 7, July 2014).
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