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Su L, Marshall IPG, Teske AP, Yao H, Li J. Genomic characterization of the bacterial phylum Candidatus Effluviviacota, a cosmopolitan member of the global seep microbiome. mBio 2024; 15:e0099224. [PMID: 38980039 PMCID: PMC11323493 DOI: 10.1128/mbio.00992-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2024] [Accepted: 06/17/2024] [Indexed: 07/10/2024] Open
Abstract
The microbial communities of marine seep sediments contain unexplored physiological and phylogenetic diversity. Here, we examined 30 bacterial metagenome-assembled genomes (MAGs) from cold seeps in the South China Sea, the Indian Ocean, the Scotian Basin, and the Gulf of Mexico, as well as from deep-sea hydrothermal sediments in the Guaymas Basin, Gulf of California. Phylogenetic analyses of these MAGs indicate that they form a distinct phylum-level bacterial lineage, which we propose as a new phylum, Candidatus Effluviviacota, in reference to its preferential occurrence at diverse seep areas. Based on tightly clustered high-quality MAGs, we propose two new genus-level candidatus taxa, Candidatus Effluvivivax and Candidatus Effluvibates. Genomic content analyses indicate that Candidatus Effluviviacota are chemoheterotrophs that harbor the Embden-Meyerhof-Parnas glycolysis pathway. They gain energy by fermenting organic substrates. Additionally, they display potential capabilities for the degradation of cellulose, hemicellulose, starch, xylan, and various peptides. Extracellular anaerobic respiration appears to rely on metals as electron acceptors, with electron transfer primarily mediated by multiheme cytochromes and by a flavin-based extracellular electron transfer (EET) mechanism that involves NADH-quinone oxidoreductase-demethylmenaquinone-synthesizing enzymes, uncharacterized membrane proteins, and flavin-binding proteins, also known as the NUO-DMK-EET-FMN complex. The heterogeneity within the Ca. Effluviviacota phylum suggests varying roles in energy metabolism among different genera. While NUO-DMK-EET-FMN electron transfer has been reported predominantly in Gram-positive bacteria, it is now identified in Ca. Effluviviacota as well. We detected the presence of genes associated with bacterial microcompartments in Ca. Effluviviacota, which can promote specific metabolic processes and protect the cytosol from toxic intermediates. IMPORTANCE The newly discovered bacterial phylum Candidatus Effluviviacota is widespread across diverse seepage ecosystems, marine environments, and freshwater environments, with a notable preference for cold seeps. While maintaining an average abundance of approximately 1% in the global gene catalog of cold seep habitats, it has not hitherto been characterized. The metabolic versatility of Ca. Effluviviacota in anaerobic carbon, hydrogen, and metal cycling aligns with its prevalence in anoxic niches, with a preference for cold seep environments. Variations in metabolic potential between Ca. Effluvivivax and Ca. Effluvibates may contribute to shaping their respective habitat distributions.
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Affiliation(s)
- Lei Su
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
- Department of Biology, Center for Electromicrobiology (CEM), Section for Microbiology, Aarhus University, Aarhus, Denmark
| | - Ian P. G. Marshall
- Department of Biology, Center for Electromicrobiology (CEM), Section for Microbiology, Aarhus University, Aarhus, Denmark
| | - Andreas P. Teske
- Department of Earth, Marine and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Huiqiang Yao
- MLR Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Guangzhou, China
| | - Jiangtao Li
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
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Liu R, Cai R, Wang M, Zhang J, Zhang H, Li C, Sun C. Metagenomic insights into Heimdallarchaeia clades from the deep-sea cold seep and hydrothermal vent. ENVIRONMENTAL MICROBIOME 2024; 19:43. [PMID: 38909236 PMCID: PMC11193907 DOI: 10.1186/s40793-024-00585-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 06/18/2024] [Indexed: 06/24/2024]
Abstract
Heimdallarchaeia is a class of the Asgardarchaeota, are the most probable candidates for the archaeal protoeukaryote ancestor that have been identified to date. However, little is known about their life habits regardless of their ubiquitous distribution in diverse habitats, which is especially true for Heimdallarchaeia from deep-sea environments. In this study, we obtained 13 metagenome-assembled genomes (MAGs) of Heimdallarchaeia from the deep-sea cold seep and hydrothermal vent. These MAGs belonged to orders o_Heimdallarchaeales and o_JABLTI01, and most of them (9 MAGs) come from the family f_Heimdallarchaeaceae according to genome taxonomy database (GTDB). These are enriched for common eukaryote-specific signatures. Our results show that these Heimdallarchaeia have the metabolic potential to reduce sulfate (assimilatory) and nitrate (dissimilatory) to sulfide and ammonia, respectively, suggesting a previously unappreciated role in biogeochemical cycling. Furthermore, we find that they could perform both TCA and rTCA pathways coupled with pyruvate metabolism for energy conservation, fix CO2 and generate organic compounds through an atypical Wood-Ljungdahl pathway. In addition, many genes closely associated with bacteriochlorophyll and carotenoid biosynthesis, and oxygen-dependent metabolic pathways are identified in these Heimdallarchaeia MAGs, suggesting a potential light-utilization by pigments and microoxic lifestyle. Taken together, our results indicate that Heimdallarchaeia possess a mixotrophic lifestyle, which may give them more flexibility to adapt to the harsh deep-sea conditions.
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Affiliation(s)
- Rui Liu
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Ruining Cai
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Minxiao Wang
- Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Jing Zhang
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China
- Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Huan Zhang
- Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Chaolun Li
- Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
- Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.
| | - Chaomin Sun
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China.
- Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China.
- Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.
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3
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Zhao R, Jørgensen SL, Babbin AR. An abundant bacterial phylum with nitrite-oxidizing potential in oligotrophic marine sediments. Commun Biol 2024; 7:449. [PMID: 38605091 PMCID: PMC11009272 DOI: 10.1038/s42003-024-06136-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 04/02/2024] [Indexed: 04/13/2024] Open
Abstract
Nitrite-oxidizing bacteria (NOB) are important nitrifiers whose activity regulates the availability of nitrite and dictates the magnitude of nitrogen loss in ecosystems. In oxic marine sediments, ammonia-oxidizing archaea (AOA) and NOB together catalyze the oxidation of ammonium to nitrate, but the abundance ratios of AOA to canonical NOB in some cores are significantly higher than the theoretical ratio range predicted from physiological traits of AOA and NOB characterized under realistic ocean conditions, indicating that some NOBs are yet to be discovered. Here we report a bacterial phylum Candidatus Nitrosediminicolota, members of which are more abundant than canonical NOBs and are widespread across global oligotrophic sediments. Ca. Nitrosediminicolota members have the functional potential to oxidize nitrite, in addition to other accessory functions such as urea hydrolysis and thiosulfate reduction. While one recovered species (Ca. Nitrosediminicola aerophilus) is generally confined within the oxic zone, another (Ca. Nitrosediminicola anaerotolerans) additionally appears in anoxic sediments. Counting Ca. Nitrosediminicolota as a nitrite-oxidizer helps to resolve the apparent abundance imbalance between AOA and NOB in oxic marine sediments, and thus its activity may exert controls on the nitrite budget.
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Affiliation(s)
- Rui Zhao
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - Steffen L Jørgensen
- Centre for Deep-Sea Research, Department of Earth Science, University of Bergen, Bergen, Norway
| | - Andrew R Babbin
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
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4
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Fu L, Liu Y, Wang M, Lian C, Cao L, Wang W, Sun Y, Wang N, Li C. The diversification and potential function of microbiome in sediment-water interface of methane seeps in South China Sea. Front Microbiol 2024; 15:1287147. [PMID: 38380093 PMCID: PMC10878133 DOI: 10.3389/fmicb.2024.1287147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 01/11/2024] [Indexed: 02/22/2024] Open
Abstract
The sediment-water interfaces of cold seeps play important roles in nutrient transportation between seafloor and deep-water column. Microorganisms are the key actors of biogeochemical processes in this interface. However, the knowledge of the microbiome in this interface are limited. Here we studied the microbial diversity and potential metabolic functions by 16S rRNA gene amplicon sequencing at sediment-water interface of two active cold seeps in the northern slope of South China Sea, Lingshui and Site F cold seeps. The microbial diversity and potential functions in the two cold seeps are obviously different. The microbial diversity of Lingshui interface areas, is found to be relatively low. Microbes associated with methane consumption are enriched, possibly due to the large and continuous eruptions of methane fluids. Methane consumption is mainly mediated by aerobic oxidation and denitrifying anaerobic methane oxidation (DAMO). The microbial diversity in Site F is higher than Lingshui. Fluids from seepage of Site F are mitigated by methanotrophic bacteria at the cyclical oxic-hypoxic fluctuating interface where intense redox cycling of carbon, sulfur, and nitrogen compounds occurs. The primary modes of microbial methane consumption are aerobic methane oxidation, along with DAMO, sulfate-dependent anaerobic methane oxidation (SAMO). To sum up, anaerobic oxidation of methane (AOM) may be underestimated in cold seep interface microenvironments. Our findings highlight the significance of AOM and interdependence between microorganisms and their environments in the interface microenvironments, providing insights into the biogeochemical processes that govern these unique ecological systems.
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Affiliation(s)
- Lulu Fu
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laoshan Laboratory, Qingdao, China
| | - Yanjun Liu
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Minxiao Wang
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laoshan Laboratory, Qingdao, China
| | - Chao Lian
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Lei Cao
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Weicheng Wang
- State Key Laboratory of Mariculture Breeding, Key Laboratory of Marine Biotechnology of Fujian Province, Institute of Oceanology, College of Marine Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yan Sun
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laoshan Laboratory, Qingdao, China
| | - Nan Wang
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laoshan Laboratory, Qingdao, China
| | - Chaolun Li
- Center of Deep Sea Research and Key Laboratory of Marine Ecology and Environmental Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laoshan Laboratory, Qingdao, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
- South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
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5
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Ji M, Smith AF, Rattray JE, England WE, Hubert CRJ. Potential for natural attenuation of crude oil hydrocarbons in benthic microbiomes near coastal communities in Kivalliq, Nunavut, Canada. MARINE POLLUTION BULLETIN 2023; 196:115557. [PMID: 37776739 DOI: 10.1016/j.marpolbul.2023.115557] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 09/04/2023] [Accepted: 09/16/2023] [Indexed: 10/02/2023]
Abstract
Oil spilled in marine environments can settle to the seafloor through aggregation and sedimentation processes. This has been predicted to be especially relevant in the Arctic due to plankton blooms initiated by melting sea ice. These conditions exist in the Kivalliq region in Nunavut, Canada, where elevated shipping traffic has increased the risk of accidental spills. Experimental microcosms combining surface sediment and crude oil were incubated at 4 °C over 21 weeks to evaluate the biodegradation potential of seabed microbiomes. Sediments sampled near the communities of Arviat and Chesterfield Inlet were assessed for biodegradation capabilities by combining hydrocarbon geochemistry with 16S rRNA gene and metagenomic sequencing, revealing decreased microbial diversity but enrichment of oil-degrading taxa. Alkane and aromatic hydrocarbon losses corresponded to detection of genes and genomes that encode enzymes for aerobic biodegradation of these compounds, pointing to the utility of marine microbiome surveys for predicting the fate of oil released into Arctic marine environments.
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Affiliation(s)
- Meng Ji
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
| | - Alastair F Smith
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Jayne E Rattray
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Whitney E England
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Casey R J Hubert
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
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6
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Pavlova ON, Tupikin AE, Chernitsyna SM, Bukin YS, Lomakina AV, Pogodaeva TV, Nikonova AA, Bukin SV, Zemskaya TI, Kabilov MR. Description and Genomic Analysis of the First Facultatively Lithoautotrophic, Thermophilic Bacteria of the Genus Thermaerobacter Isolated from Low-temperature Sediments of Lake Baikal. MICROBIAL ECOLOGY 2023; 86:1604-1619. [PMID: 36717392 DOI: 10.1007/s00248-023-02182-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
Members of the genus Thermaerobacter belong to the phylum Firmicutes and all isolates characterised to date are strictly aerobic and thermophilic. They were isolated from a mud sample of the Challenger Deep in the Mariana Trench, hydrothermal vents, and silt compost. A novel thermophilic, facultatively lithoautotrophic bacteria of the genus Thermaerobacter, strain PB12/4term (=VKM B-3151T), with a metabolism that is uncharacteristic of the type species, was isolated from low-temperature surface sediments near the Posolsk Bank methane seep, Lake Baikal, Russia. The new strain grows with molecular hydrogen as electron donor, elemental sulfur, and thiosulfate as electron acceptors, and CO2/[Formula: see text] as carbon source. The genome of strain PB12/4term consists of one chromosome with a total length of 2.820.915 bp and the G+C content of the genomic DNA was 72.2%. The phylogenomic reconstruction based on 120 conserved bacterial single-copy proteins revealed that strain PB12/4term belongs to the genus Thermaerobacter within in the class Thermaerobacteria, phylum Firmicutes_E. The strain PB12/4term is closely related to Thermaerobacter subterraneus DSM 13965 (ANI=95.08%, AF=0.91) and Thermaerobacter marianensis DSM 12885 (ANI=84.98%, AF=0.77). Genomic and experimental data confirm the ability of the Thermaerobacter PB12/4term pure culture to facultatively lithotrophic growth, which is provided by the presence of [NiFe]hydrogenase enzymes that are absent in T. marianensis DSM 12885 and T. subterraneus DSM 13965. The data obtained on the physiological and biochemical differences of strain PB12/4term provide a deeper insight into the species diversity and functional activity of the genus Thermaerobacter.
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Affiliation(s)
- O N Pavlova
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia.
| | - A E Tupikin
- SB RAS Genomics Core Facility, Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
| | - S M Chernitsyna
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - Y S Bukin
- Laboratory of Genosystematics, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - A V Lomakina
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - T V Pogodaeva
- Laboratory of Hydrochemistry and Atmosphere Chemistry, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - A A Nikonova
- Laboratory of Chromatography, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - S V Bukin
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - T I Zemskaya
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - M R Kabilov
- SB RAS Genomics Core Facility, Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
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Ferguson DK, Li C, Chakraborty A, Gittins DA, Fowler M, Webb J, Campbell C, Morrison N, MacDonald A, Hubert CRJ. Multi-year seabed environmental baseline in deep-sea offshore oil prospective areas established using microbial biodiversity. MARINE POLLUTION BULLETIN 2023; 194:115308. [PMID: 37517246 DOI: 10.1016/j.marpolbul.2023.115308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 07/14/2023] [Accepted: 07/16/2023] [Indexed: 08/01/2023]
Abstract
Microorganisms are the ocean's first responders to marine pollution events, yet baseline studies rarely focus on microbial communities. Temporal and spatial microbial biodiversity baselines were established using bacterial 16S rRNA gene amplicon sequencing of seafloor sediments in a deep-water oil prospective area along the Scotian Slope off Canada's east coast sampled during 2015-2018. Bacterial diversity was generally similar in space and time, with members of the family Woeseiaceae detected consistently in >1 % relative abundance, similar to seabed sediments in other parts of the world. Anomalous biodiversity results at one site featured lower Woeseiaceae as well as higher levels of bacterial groups specifically associated with cold seeps such as Aminicenantes. This was unexpected given that site selection was based on sediment geochemistry not revealing any petroleum hydrocarbons in these locations. This finding highlights the sensitivity and specificity of microbial DNA sequencing in environmental monitoring. Microbiome assessments like this one represent an important strategy for incorporating microbial biodiversity as a new and useful metric for establishing robust environmental baselines that are necessary for understanding ecosystem responses to marine pollution.
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Affiliation(s)
- Deidra K Ferguson
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
| | - Carmen Li
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Anirban Chakraborty
- Department of Biological Sciences, Idaho State University, Pocatello, ID, USA
| | - Daniel A Gittins
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Martin Fowler
- Applied Petroleum Technology Canada, Calgary, Alberta, Canada
| | - Jamie Webb
- Applied Petroleum Technology Canada, Calgary, Alberta, Canada
| | - Calvin Campbell
- Natural Resources Canada, Geological Survey of Canada-Atlantic, Dartmouth, Nova Scotia, Canada
| | - Natasha Morrison
- Nova Scotia Department of Natural Resources and Renewables, Government of Nova Scotia, Halifax, Nova Scotia, Canada
| | - Adam MacDonald
- Nova Scotia Department of Natural Resources and Renewables, Government of Nova Scotia, Halifax, Nova Scotia, Canada
| | - Casey R J Hubert
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
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8
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Chen Y, Dai T, Li N, Li Q, Lyu Y, Di P, Lyu L, Zhang S, Li J. Environmental heterogeneity shapes the C and S cycling-associated microbial community in Haima's cold seeps. Front Microbiol 2023; 14:1199853. [PMID: 37502402 PMCID: PMC10370420 DOI: 10.3389/fmicb.2023.1199853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 06/07/2023] [Indexed: 07/29/2023] Open
Abstract
Environmental heterogeneity in cold seeps is usually reflected by different faunal aggregates. The sediment microbiome, especially the geochemical cycling-associated communities, sustains the ecosystem through chemosynthesis. To date, few studies have paid attention to the structuring and functioning of geochemical cycling-associated communities relating to environmental heterogeneity in different faunal aggregates of cold seeps. In this study, we profiled the microbial community of four faunal aggregates in the Haima cold seep, South China Sea. Through a combination of geochemical and meta-omics approaches, we have found that geochemical variables, such as sulfate and calcium, exhibited a significant variation between different aggregates, indicating changes in the methane flux. Anaerobic methanotrophic archaea (ANME), sulfate-reducing, and sulfide-oxidizing bacteria (SRB and SOB) dominated the microbial community but varied in composition among the four aggregates. The diversity of archaea and bacteria exhibited a strong correlation between sulfate, calcium, and silicate. Interspecies co-exclusion inferred by molecular ecological network analysis increased from non-seep to clam aggregates and peaked at the mussel aggregate. The networked geochemical cycling-associated species showed an obvious aggregate-specific distribution pattern. Notably, hydrocarbon oxidation and sulfate reduction by ANME and SRB produced carbonate and sulfide, driving the alkalization of the sediment environment, which may impact the microbial communities. Collectively, these results highlighted that geofluid and microbial metabolism together resulted in environmental heterogeneity, which shaped the C and S cycling-associated microbial community.
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Affiliation(s)
- Yu Chen
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
| | - Tianjiao Dai
- School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, China
| | - Niu Li
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
| | - Qiqi Li
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
| | - Yuanjiao Lyu
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
| | - Pengfei Di
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
| | - Lina Lyu
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
| | - Si Zhang
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
| | - Jie Li
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, Guangdong, China
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9
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Zorz J, Li C, Chakraborty A, Gittins DA, Surcon T, Morrison N, Bennett R, MacDonald A, Hubert CRJ. SituSeq: an offline protocol for rapid and remote Nanopore 16S rRNA amplicon sequence analysis. ISME COMMUNICATIONS 2023; 3:33. [PMID: 37081077 PMCID: PMC10119094 DOI: 10.1038/s43705-023-00239-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 03/27/2023] [Accepted: 04/04/2023] [Indexed: 04/22/2023]
Abstract
Microbiome analysis through 16S rRNA gene sequencing is a crucial tool for understanding the microbial ecology of any habitat or ecosystem. However, workflows require large equipment, stable internet, and extensive computing power such that most of the work is performed far away from sample collection in both space and time. Performing amplicon sequencing and analysis at sample collection would have positive implications in many instances including remote fieldwork and point-of-care medical diagnoses. Here we present SituSeq, an offline and portable workflow for the sequencing and analysis of 16S rRNA gene amplicons using Nanopore sequencing and a standard laptop computer. SituSeq was validated by comparing Nanopore 16S rRNA gene amplicons, Illumina 16S rRNA gene amplicons, and Illumina metagenomes, sequenced using the same environmental DNA. Comparisons revealed consistent community composition, ecological trends, and sequence identity across platforms. Correlation between the abundance of taxa in each taxonomic level in Illumina and Nanopore data sets was high (Pearson's r > 0.9), and over 70% of Illumina 16S rRNA gene sequences matched a Nanopore sequence with greater than 97% sequence identity. On board a research vessel on the open ocean, SituSeq was used to analyze amplicon sequences from deep sea sediments less than 2 h after sequencing, and 8 h after sample collection. The rapidly available results informed decisions about subsequent sampling in near real-time while the offshore expedition was still underway. SituSeq is a portable and user-friendly workflow that helps to bring the power of microbial genomics and diagnostics to many more researchers and situations.
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Affiliation(s)
- Jackie Zorz
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada.
| | - Carmen Li
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Anirban Chakraborty
- Department of Biological Sciences, Idaho State University, Pocatello, ID, USA
| | - Daniel A Gittins
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Taylor Surcon
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Natasha Morrison
- Department of Natural Resources and Renewables, Government of Nova Scotia, Halifax, NS, Canada
| | - Robbie Bennett
- Natural Resources Canada, Geological Survey of Canada-Atlantic, Dartmouth, NS, Canada
| | - Adam MacDonald
- Department of Natural Resources and Renewables, Government of Nova Scotia, Halifax, NS, Canada
| | - Casey R J Hubert
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
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10
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Dong X, Peng Y, Wang M, Woods L, Wu W, Wang Y, Xiao X, Li J, Jia K, Greening C, Shao Z, Hubert CRJ. Evolutionary ecology of microbial populations inhabiting deep sea sediments associated with cold seeps. Nat Commun 2023; 14:1127. [PMID: 36854684 PMCID: PMC9974965 DOI: 10.1038/s41467-023-36877-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 02/21/2023] [Indexed: 03/02/2023] Open
Abstract
Deep sea cold seep sediments host abundant and diverse microbial populations that significantly influence biogeochemical cycles. While numerous studies have revealed their community structure and functional capabilities, little is known about genetic heterogeneity within species. Here, we examine intraspecies diversity patterns of 39 abundant species identified in sediment layers down to 430 cm below the sea floor across six cold seep sites. These populations are grouped as aerobic methane-oxidizing bacteria, anaerobic methanotrophic archaea and sulfate-reducing bacteria. Different evolutionary trajectories are observed at the genomic level among these physiologically and phylogenetically diverse populations, with generally low rates of homologous recombination and strong purifying selection. Functional genes related to methane (pmoA and mcrA) and sulfate (dsrA) metabolisms are under strong purifying selection in most species investigated. These genes differ in evolutionary trajectories across phylogenetic clades but are functionally conserved across sites. Intrapopulation diversification of genomes and their mcrA and dsrA genes is depth-dependent and subject to different selection pressure throughout the sediment column redox zones at different sites. These results highlight the interplay between ecological processes and the evolution of key bacteria and archaea in deep sea cold seep extreme environments, shedding light on microbial adaptation in the subseafloor biosphere.
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Affiliation(s)
- Xiyang Dong
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, 361005, China.
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, China.
| | - Yongyi Peng
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, 361005, China
- School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China
| | - Muhua Wang
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, China
- School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China
| | - Laura Woods
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, 3800, Australia
| | - Wenxue Wu
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, China
- School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China
- State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou, 570228, China
| | - Yong Wang
- Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China
| | - Xi Xiao
- Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou, 510075, China
| | - Jiwei Li
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, 572000, China
| | - Kuntong Jia
- School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China
| | - Chris Greening
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, 3800, Australia
| | - Zongze Shao
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, 361005, China.
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, China.
| | - Casey R J Hubert
- Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada
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11
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Rattray JE, Chakraborty A, Elizondo G, Ellefson E, Bernard B, Brooks J, Hubert CRJ. Endospores associated with deep seabed geofluid features in the eastern Gulf of Mexico. GEOBIOLOGY 2022; 20:823-836. [PMID: 35993193 PMCID: PMC9804197 DOI: 10.1111/gbi.12517] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 05/12/2022] [Accepted: 07/11/2022] [Indexed: 06/15/2023]
Abstract
Recent studies have reported up to 1.9 × 1029 bacterial endospores in the upper kilometre of deep subseafloor marine sediments, however, little is understood about their origin and dispersal. In cold ocean environments, the presence of thermospores (endospores produced by thermophilic bacteria) suggests that distribution is governed by passive migration from warm anoxic sources possibly facilitated by geofluid flow, such as advective hydrocarbon seepage sourced from petroleum deposits deeper in the subsurface. This study assesses this hypothesis by measuring endospore abundance and distribution across 60 sites in Eastern Gulf of Mexico (EGM) sediments using a combination of the endospore biomarker 2,6-pyridine dicarboxylic acid or 'dipicolinic acid' (DPA), sequencing 16S rRNA genes of thermospores germinated in 50°C sediment incubations, petroleum geochemistry in the sediments and acoustic seabed data from sub-bottom profiling. High endospore abundance is associated with geologically active conduit features (mud volcanoes, pockmarks, escarpments and fault systems), consistent with subsurface fluid flow dispersing endospores from deep warm sources up into the cold ocean. Thermospores identified at conduit sites were most closely related to bacteria associated with the deep biosphere habitats including hydrocarbon systems. The high endospore abundance at geological seep features demonstrated here suggests that recalcitrant endospores and their chemical components (such as DPA) can be used in concert with geochemical and geophysical analyses to locate discharging seafloor features. This multiproxy approach can be used to better understand patterns of advective fluid flow in regions with complex geology like the EGM basin.
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Affiliation(s)
- Jayne E. Rattray
- Department of Biological SciencesUniversity of CalgaryCalgaryAlbertaCanada
| | - Anirban Chakraborty
- Department of Biological SciencesUniversity of CalgaryCalgaryAlbertaCanada
- Department of Biological SciencesIdaho State UniversityPocatelloIdahoUSA
| | - Gretta Elizondo
- Department of Biological SciencesUniversity of CalgaryCalgaryAlbertaCanada
| | - Emily Ellefson
- Department of Biological SciencesUniversity of CalgaryCalgaryAlbertaCanada
- Geological SciencesStanford UniversityStanfordCaliforniaUSA
| | | | | | - Casey R. J. Hubert
- Department of Biological SciencesUniversity of CalgaryCalgaryAlbertaCanada
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12
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Gittins DA, Desiage PA, Morrison N, Rattray JE, Bhatnagar S, Chakraborty A, Zorz J, Li C, Horanszky O, Cramm MA, Bisiach F, Bennett R, Webb J, MacDonald A, Fowler M, Campbell DC, Hubert CRJ. Geological processes mediate a microbial dispersal loop in the deep biosphere. SCIENCE ADVANCES 2022; 8:eabn3485. [PMID: 36026445 PMCID: PMC9417182 DOI: 10.1126/sciadv.abn3485] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The deep biosphere is the largest microbial habitat on Earth and features abundant bacterial endospores. Whereas dormancy and survival at theoretical energy minima are hallmarks of microbial physiology in the subsurface, ecological processes such as dispersal and selection in the deep biosphere remain poorly understood. We investigated the biogeography of dispersing bacteria in the deep sea where upward hydrocarbon seepage was confirmed by acoustic imagery and geochemistry. Thermophilic endospores in the permanently cold seabed correlated with underlying seep conduits reveal geofluid-facilitated cell migration pathways originating in deep petroleum-bearing sediments. Endospore genomes highlight adaptations to life in anoxic petroleum systems and bear close resemblance to oil reservoir microbiomes globally. Upon transport out of the subsurface, viable thermophilic endospores reenter the geosphere by sediment burial, enabling germination and environmental selection at depth where new petroleum systems establish. This microbial dispersal loop circulates living biomass in and out of the deep biosphere.
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Affiliation(s)
- Daniel A. Gittins
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
- Corresponding author.
| | | | - Natasha Morrison
- Department of Natural Resources and Renewables, Government of Nova Scotia, Halifax, Canada
| | - Jayne E. Rattray
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Srijak Bhatnagar
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
| | | | - Jackie Zorz
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Carmen Li
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Oliver Horanszky
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Margaret A. Cramm
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Francesco Bisiach
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
| | - Robbie Bennett
- Natural Resources Canada, Geological Survey of Canada-Atlantic, Dartmouth, Canada
| | - Jamie Webb
- Applied Petroleum Technology, Calgary, Canada
| | - Adam MacDonald
- Department of Natural Resources and Renewables, Government of Nova Scotia, Halifax, Canada
| | | | - D. Calvin Campbell
- Natural Resources Canada, Geological Survey of Canada-Atlantic, Dartmouth, Canada
| | - Casey R. J. Hubert
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, Calgary, Canada
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13
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Pavlova ON, Izosimova ON, Chernitsyna SM, Ivanov VG, Pogodaeva TV, Khabuev AV, Gorshkov AG, Zemskaya TI. Anaerobic oxidation of petroleum hydrocarbons in enrichment cultures from sediments of the Gorevoy Utes natural oil seep under methanogenic and sulfate-reducing conditions. MICROBIAL ECOLOGY 2022; 83:899-915. [PMID: 34255112 DOI: 10.1007/s00248-021-01802-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 06/18/2021] [Indexed: 06/13/2023]
Abstract
This article presents the first experimental data on the ability of microbial communities from sediments of the Gorevoy Utes natural oil seep to degrade petroleum hydrocarbons under anaerobic conditions. Like in marine ecosystems associated with oil discharge, available electron acceptors, in particular sulfate ions, affect the composition of the microbial community and the degree of hydrocarbon conversion. The cultivation of the surface sediments under sulfate-reducing conditions led to the formation of a more diverse bacterial community and greater loss of n-alkanes (28%) in comparison to methanogenic conditions (6%). Microbial communities of both surface and deep sediments are more oriented to degrade polycyclic aromatic hydrocarbons (PAHs), to which the degree of the PAH conversion testifies (up to 46%) irrespective of the present electron acceptors. Microorganisms with the uncultured closest homologues from thermal habitats, sediments of mud volcanoes, and environments contaminated with hydrocarbons mainly represented microbial communities of enrichment cultures. The members of the phyla Firmicutes, Chloroflexi, and Caldiserica (OP5), as well as the class Deltaproteobacteria and Methanomicrobia, were mostly found in enrichment cultures. The influence of gas-saturated fluids may be responsible for the presence in the bacterial 16S rRNA gene libraries of the sequences of "rare taxa": Planctomycetes, Ca. Atribacteria (OP9), Ca. Armatimonadetes (OP10), Ca. Latescibacteria (WS3), Ca. division (AC1), Ca. division (OP11), and Ca. Parcubacteria (OD1), which can be involved in hydrocarbon oxidation.
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Affiliation(s)
- O N Pavlova
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia.
| | - O N Izosimova
- Laboratory of Chromatography, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - S M Chernitsyna
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - V G Ivanov
- Laboratory of Hydrology and Hydrophysics, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - T V Pogodaeva
- Laboratory of Hydrochemistry and Atmosphere Chemistry, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - A V Khabuev
- Laboratory of Lake Baikal Geology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - A G Gorshkov
- Laboratory of Chromatography, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
| | - T I Zemskaya
- Laboratory of Hydrocarbon Microbiology, Limnological Institute, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
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14
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Zhou YL, Mara P, Cui GJ, Edgcomb VP, Wang Y. Microbiomes in the Challenger Deep slope and bottom-axis sediments. Nat Commun 2022; 13:1515. [PMID: 35314706 PMCID: PMC8938466 DOI: 10.1038/s41467-022-29144-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 03/01/2022] [Indexed: 12/24/2022] Open
Abstract
Hadal trenches are the deepest and most remote regions of the ocean. The 11-kilometer deep Challenger Deep is the least explored due to the technical challenges of sampling hadal depths. It receives organic matter and heavy metals from the overlying water column that accumulate differently across its V-shaped topography. Here, we collected sediments across the slope and bottom-axis of the Challenger Deep that enable insights into its in situ microbial communities. Analyses of 586 metagenome-assembled genomes retrieved from 37 metagenomes show distinct diversity and metabolic capacities between bottom-axis and slope sites. 26% of prokaryotic 16S rDNA reads in metagenomes were novel, with novelty increasing with water and sediment depths. These predominantly heterotrophic microbes can recycle macromolecules and utilize simple and complex hydrocarbons as carbon sources. Metagenome and metatranscriptome data support reduction and biotransformation of arsenate for energy gain in sediments that present a two-fold greater accumulation of arsenic compared to non-hadal sites. Complete pathways for anaerobic ammonia oxidation are predominantly identified in genomes recovered from bottom-axis sediments compared to slope sites. Our results expand knowledge of microbially-mediated elemental cycling in hadal sediments, and reveal differences in distribution of processes involved in nitrogen loss across the trench.
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Affiliation(s)
- Ying-Li Zhou
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Paraskevi Mara
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Guo-Jie Cui
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Virginia P Edgcomb
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Yong Wang
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, Hainan, China.
- Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen, China.
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15
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Stimulated Organic Carbon Cycling and Microbial Community Shift Driven by a Simulated Cold-Seep Eruption. mBio 2022; 13:e0008722. [PMID: 35229641 PMCID: PMC8941925 DOI: 10.1128/mbio.00087-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cold seeps are a major methane source in marine systems, and microbe-mediated anaerobic oxidation of methane (AOM) serves as an effective barrier for preventing methane emissions from sediment to water. However, how the periodic eruption of cold seeps drives the microbial community shift and further affects carbon cycling has been largely neglected, mainly due to the technical challenge of analyzing the in situ communities undergoing such geological events. Using a continuously running high-pressure bioreactor to simulate these events, we found that under the condition of simulated eruptions, the abundance of AOM-related species decreased, and some methane was oxidized to methyl compounds to feed heterotrophs. The methanogenic archaeon Methanolobus replaced ANME-2a as the dominant archaeal group; moreover, the levels of methylotrophic bacteria, such as Pseudomonas, Halomonas, and Methylobacter, quickly increased, while those of sulfate-reducing bacteria decreased. According to the genomic analysis, Methylobacter played an important role in incomplete methane oxidation during eruptions; this process was catalyzed by the genes pmoABC under anaerobic conditions when the methane pressure was high, possibly generating organic carbon. Additionally, the findings showed that methyl compounds can also be released to the environment during methanogenesis and AOM under eruption conditions when the methane pressure is high.
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16
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Scheffer G, Hubert CRJ, Enning DR, Lahme S, Mand J, de Rezende JR. Metagenomic Investigation of a Low Diversity, High Salinity Offshore Oil Reservoir. Microorganisms 2021; 9:2266. [PMID: 34835392 PMCID: PMC8621343 DOI: 10.3390/microorganisms9112266] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/27/2021] [Accepted: 09/28/2021] [Indexed: 12/22/2022] Open
Abstract
Oil reservoirs can represent extreme environments for microbial life due to low water availability, high salinity, high pressure and naturally occurring radionuclides. This study investigated the microbiome of saline formation water samples from a Gulf of Mexico oil reservoir. Metagenomic analysis and associated anaerobic enrichment cultures enabled investigations into metabolic potential for microbial activity and persistence in this environment given its high salinity (4.5%) and low nutrient availability. Preliminary 16S rRNA gene amplicon sequencing revealed very low microbial diversity. Accordingly, deep shotgun sequencing resulted in nine metagenome-assembled genomes (MAGs), including members of novel lineages QPJE01 (genus level) within the Halanaerobiaceae, and BM520 (family level) within the Bacteroidales. Genomes of the nine organisms included respiratory pathways such as nitrate reduction (in Arhodomonas, Flexistipes, Geotoga and Marinobacter MAGs) and thiosulfate reduction (in Arhodomonas, Flexistipes and Geotoga MAGs). Genomic evidence for adaptation to high salinity, withstanding radioactivity, and metal acquisition was also observed in different MAGs, possibly explaining their occurrence in this extreme habitat. Other metabolic features included the potential for quorum sensing and biofilm formation, and genes for forming endospores in some cases. Understanding the microbiomes of deep biosphere environments sheds light on the capabilities of uncultivated subsurface microorganisms and their potential roles in subsurface settings, including during oil recovery operations.
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Affiliation(s)
- Gabrielle Scheffer
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada;
| | - Casey R. J. Hubert
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada;
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK; (S.L.); (J.R.d.R.)
| | - Dennis R. Enning
- Faculty of Life Sciences and Technology, Berlin University of Applied Sciences and Technology, D-13347 Berlin, Germany;
| | - Sven Lahme
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK; (S.L.); (J.R.d.R.)
- Exxon Mobil Upstream Research Company, Spring, TX 77389, USA;
| | - Jaspreet Mand
- Exxon Mobil Upstream Research Company, Spring, TX 77389, USA;
| | - Júlia R. de Rezende
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK; (S.L.); (J.R.d.R.)
- The Lyell Centre, Heriot-Watt University, Edinburgh EH14 4AS, UK
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17
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Eight metagenome-assembled genomes provide evidence for microbial adaptation in 20,000 to 1,000,000-year-old Siberian permafrost. Appl Environ Microbiol 2021; 87:e0097221. [PMID: 34288700 DOI: 10.1128/aem.00972-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
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 Siberia 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 Aminicenantes, Atribacteria, Chloroflexi, and Actinobacteria within bacteria and Thermoprofundales within archaea. MAGs from these taxa have previously been obtained from non-permafrost 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 higher proportions of clusters of orthologous genes (COGs) from 'Energy production and conversion' and 'Carbohydrate transport and metabolism' than their non-permafrost counterparts. They also contained genes for trehalose synthesis, thymine metabolism, mevalonate biosynthesis and cellulose degradation that were less prevalent in non-permafrost 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 in high enough quality to assemble MAGs from microorganisms with adaptations to subsist long-term freezing in this extreme environment. Importance 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 in these extreme low temperature and energy conditions. This will aid understanding of how they will change with the environment. This study presents genomic data from this unique environment aged ∼20,000 to 1,000,000-years-old.
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18
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Glass JB, Ranjan P, Kretz CB, Nunn BL, Johnson AM, Xu M, McManus J, Stewart FJ. Microbial metabolism and adaptations in Atribacteria-dominated methane hydrate sediments. Environ Microbiol 2021; 23:4646-4660. [PMID: 34190392 DOI: 10.1111/1462-2920.15656] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 06/28/2021] [Indexed: 12/12/2022]
Abstract
Gas hydrates harbour gigatons of natural gas, yet their microbiomes remain understudied. We bioprospected 16S rRNA amplicons, metagenomes, and metaproteomes from methane hydrate-bearing sediments under Hydrate Ridge (offshore Oregon, USA, ODP Site 1244, 2-69 mbsf) for novel microbial metabolic and biosynthetic potential. Atribacteria sequences generally increased in relative sequence abundance with increasing sediment depth. Most Atribacteria ASVs belonged to JS-1-Genus 1 and clustered with other sequences from gas hydrate-bearing sediments. We recovered 21 metagenome-assembled genomic bins spanning three geochemical zones in the sediment core: the sulfate-methane transition zone, the metal (iron/manganese) reduction zone, and the gas hydrate stability zone. We found evidence for bacterial fermentation as a source of acetate for aceticlastic methanogenesis and as a driver of iron reduction in the metal reduction zone. In multiple zones, we identified a Ni-Fe hydrogenase-Na+ /H+ antiporter supercomplex (Hun) in Atribacteria and Firmicutes bins and in other deep subsurface bacteria and cultured hyperthermophiles from the Thermotogae phylum. Atribacteria expressed tripartite ATP-independent transporters downstream from a novel regulator (AtiR). Atribacteria also possessed adaptations to survive extreme conditions (e.g. high salt brines, high pressure and cold temperatures) including the ability to synthesize the osmolyte di-myo-inositol-phosphate as well as expression of K+ -stimulated pyrophosphatase and capsule proteins.
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Affiliation(s)
- Jennifer B Glass
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Piyush Ranjan
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | | | - Brook L Nunn
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Abigail M Johnson
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Manlin Xu
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - James McManus
- Bigelow Laboratory for Ocean Sciences, East Boothbay, ME, USA
| | - Frank J Stewart
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA.,Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA
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19
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Marlow JJ, Hoer D, Jungbluth SP, Reynard LM, Gartman A, Chavez MS, El-Naggar MY, Tuross N, Orphan VJ, Girguis PR. Carbonate-hosted microbial communities are prolific and pervasive methane oxidizers at geologically diverse marine methane seep sites. Proc Natl Acad Sci U S A 2021; 118:e2006857118. [PMID: 34161255 PMCID: PMC8237665 DOI: 10.1073/pnas.2006857118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
At marine methane seeps, vast quantities of methane move through the shallow subseafloor, where it is largely consumed by microbial communities. This process plays an important role in global methane dynamics, but we have yet to identify all of the methane sinks in the deep sea. Here, we conducted a continental-scale survey of seven geologically diverse seafloor seeps and found that carbonate rocks from all sites host methane-oxidizing microbial communities with substantial methanotrophic potential. In laboratory-based mesocosm incubations, chimney-like carbonates from the newly described Point Dume seep off the coast of Southern California exhibited the highest rates of anaerobic methane oxidation measured to date. After a thorough analysis of physicochemical, electrical, and biological factors, we attribute this substantial metabolic activity largely to higher cell density, mineral composition, kinetic parameters including an elevated Vmax, and the presence of specific microbial lineages. Our data also suggest that other features, such as electrical conductance, rock particle size, and microbial community alpha diversity, may influence a sample's methanotrophic potential, but these factors did not demonstrate clear patterns with respect to methane oxidation rates. Based on the apparent pervasiveness within seep carbonates of microbial communities capable of performing anaerobic oxidation of methane, as well as the frequent occurrence of carbonates at seeps, we suggest that rock-hosted methanotrophy may be an important contributor to marine methane consumption.
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Affiliation(s)
- Jeffrey J Marlow
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138;
| | - Daniel Hoer
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138
| | - Sean P Jungbluth
- Department of Energy, Joint Genome Institute, Walnut Creek, CA 94720
| | - Linda M Reynard
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138
| | - Amy Gartman
- US Geological Survey Pacific Coastal and Marine Science Center, Santa Cruz, CA 95060
| | - Marko S Chavez
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089
| | - Mohamed Y El-Naggar
- Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089
| | - Noreen Tuross
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138
| | - Victoria J Orphan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - Peter R Girguis
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138;
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20
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Saif NA, Cobo-Díaz JF, Elserafy M, El-Shiekh I, Álvarez-Ordóñez A, Mouftah SF, Elhadidy M. A pilot study revealing host-associated genetic signatures for source attribution of sporadic Campylobacter jejuni infection in Egypt. Transbound Emerg Dis 2021; 69:1847-1861. [PMID: 34033263 DOI: 10.1111/tbed.14165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 05/22/2021] [Indexed: 11/30/2022]
Abstract
Campylobacter jejuni (C. jejuni), is considered among the most common bacterial causes of human bacterial gastroenteritis worldwide. The epidemiology and the transmission dynamics of campylobacteriosis in Egypt remain poorly defined due to the limited use of high-resolution typing methods. In this pilot study, we evaluated the discriminatory power of multiple typing 'gene-by-gene based' techniques to characterize C. jejuni obtained from different sources and estimate the relative contribution of different potential sources of C. jejuni infection in Egypt. Whole genome sequencing (WGS) was performed on 90 C. jejuni isolates recovered from clinical samples, retail chicken, and dairy products in Egypt from 2017 to 2018. Comparative genomic analysis was performed using conventional seven-locus multilocus sequence typing (MLST), ribosomal MLST (rMLST), core genome MLST (cgMLST), allelic variation in 15 host-segregating (HS) markers, and comparative genomic fingerprinting (CGF40). The probabilistic source attribution was performed via STRUCTURE software using MLST, CGF40, cgMLST and allelic variation in HS markers. Comparison of the discriminatory power of the aforementioned genotyping methods revealed cgMLST to be the most discriminative method, followed by HS markers. The source attribution analysis showed the role of retail chicken as a source of infection among clinical cases in Egypt when HS and cgMLST were used (64.2% and 52.3% of clinical isolates were assigned to this source, respectively). Interestingly, the cattle reservoir was also identified as a contributor to C. jejuni infection in Egypt; 35.8% and 47.7% of clinical isolates were assigned to this source by HS and cgMLST, respectively. Here, we provided evidence of the importance of using WGS typing methods to facilitate source tracking of C. jejuni. Our findings suggest the importance of non-poultry sources, together with the previously reported role of retail chicken in human campylobacteriosis in Egypt that can provide insights to inform national control measures.
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Affiliation(s)
- Nehal A Saif
- Biomedical Sciences Program, University of Science and Technology, Zewail City of Science and Technology, Giza, Egypt
| | - José F Cobo-Díaz
- Department of Food Hygiene and Technology, Universidad de León, León, Spain.,Institute of Food Science and Technology, Universidad de León, León, Spain
| | - Menattallah Elserafy
- Biomedical Sciences Program, University of Science and Technology, Zewail City of Science and Technology, Giza, Egypt.,Center for Genomics, Helmy Institute for Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
| | - Iman El-Shiekh
- Biomedical Sciences Program, University of Science and Technology, Zewail City of Science and Technology, Giza, Egypt.,Center for Genomics, Helmy Institute for Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
| | - Avelino Álvarez-Ordóñez
- Department of Food Hygiene and Technology, Universidad de León, León, Spain.,Institute of Food Science and Technology, Universidad de León, León, Spain
| | - Shaimaa F Mouftah
- Biomedical Sciences Program, University of Science and Technology, Zewail City of Science and Technology, Giza, Egypt
| | - Mohamed Elhadidy
- Biomedical Sciences Program, University of Science and Technology, Zewail City of Science and Technology, Giza, Egypt.,Department of Bacteriology, Mycology, and Immunology, Faculty of Veterinary Medicine, Mansoura University, Mansoura, Egypt
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21
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Teske A, Wegener G, Chanton JP, White D, MacGregor B, Hoer D, de Beer D, Zhuang G, Saxton MA, Joye SB, Lizarralde D, Soule SA, Ruff SE. Microbial Communities Under Distinct Thermal and Geochemical Regimes in Axial and Off-Axis Sediments of Guaymas Basin. Front Microbiol 2021; 12:633649. [PMID: 33643265 PMCID: PMC7906980 DOI: 10.3389/fmicb.2021.633649] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 01/12/2021] [Indexed: 01/04/2023] Open
Abstract
Cold seeps and hydrothermal vents are seafloor habitats fueled by subsurface energy sources. Both habitat types coexist in Guaymas Basin in the Gulf of California, providing an opportunity to compare microbial communities with distinct physiologies adapted to different thermal regimes. Hydrothermally active sites in the southern Guaymas Basin axial valley, and cold seep sites at Octopus Mound, a carbonate mound with abundant methanotrophic cold seep fauna at the Central Seep location on the northern off-axis flanking regions, show consistent geochemical and microbial differences between hot, temperate, cold seep, and background sites. The changing microbial actors include autotrophic and heterotrophic bacterial and archaeal lineages that catalyze sulfur, nitrogen, and methane cycling, organic matter degradation, and hydrocarbon oxidation. Thermal, biogeochemical, and microbiological characteristics of the sampling locations indicate that sediment thermal regime and seep-derived or hydrothermal energy sources structure the microbial communities at the sediment surface.
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Affiliation(s)
- Andreas Teske
- Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Gunter Wegener
- Max-Planck-Institute for Marine Microbiology, Bremen, Germany.,MARUM, Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Jeffrey P Chanton
- Department of Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, FL, United States
| | - Dylan White
- Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Barbara MacGregor
- Department of Marine Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.,Department of Earth and Environmental Sciences, University of Minnesota, St. Paul, MI, United States
| | - Daniel Hoer
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, United States.,United States Environmental Protection Agency, Research Triangle Park, NC, United States
| | - Dirk de Beer
- Max-Planck-Institute for Marine Microbiology, Bremen, Germany
| | - Guangchao Zhuang
- Frontiers Science Centre for Deep Ocean Multispheres and Earth System (FDOMES)/Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, China.,Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Ocean University of China, Qingdao, China.,Department of Marine Sciences, University of Georgia, Athens, GA, United States
| | - Matthew A Saxton
- Department of Marine Sciences, University of Georgia, Athens, GA, United States.,Department of Biological Sciences, Miami University, Oxford, OH, United States
| | - Samantha B Joye
- Department of Marine Sciences, University of Georgia, Athens, GA, United States
| | - Daniel Lizarralde
- Geology & Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United States
| | - S Adam Soule
- Geology & Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United States
| | - S Emil Ruff
- Marine Biological Laboratory, The Ecosystems Center, Woods Hole, MA, United States.,Marine Biological Laboratory, The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Woods Hole, MA, United States
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22
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Abstract
Marine sediment covers 70% of Earth’s surface and harbors as much biomass as seawater. However, the global taxonomic diversity of marine sedimentary communities, and the spatial distribution of that diversity remain unclear. We investigated microbial composition from 40 globally distributed sampling locations, spanning sediment depths of 0.1 to 678 m. Statistical analysis reveals that oxygen presence or absence and organic carbon concentration are key environmental factors for defining taxonomic composition and diversity of marine sedimentary communities. Global marine sedimentary taxonomic richness predicted by species–area relationship models is 7.85 × 103 to 6.10 × 105 for Archaea and 3.28 × 104 to 2.46 × 106 for Bacteria as amplicon sequence variants, which is comparable to the richness in seawater and that in topsoil. Microbial life in marine sediment contributes substantially to global biomass and is a crucial component of the Earth system. Subseafloor sediment includes both aerobic and anaerobic microbial ecosystems, which persist on very low fluxes of bioavailable energy over geologic time. However, the taxonomic diversity of the marine sedimentary microbial biome and the spatial distribution of that diversity have been poorly constrained on a global scale. We investigated 299 globally distributed sediment core samples from 40 different sites at depths of 0.1 to 678 m below the seafloor. We obtained ∼47 million 16S ribosomal RNA (rRNA) gene sequences using consistent clean subsampling and experimental procedures, which enabled accurate and unbiased comparison of all samples. Statistical analysis reveals significant correlations between taxonomic composition, sedimentary organic carbon concentration, and presence or absence of dissolved oxygen. Extrapolation with two fitted species–area relationship models indicates taxonomic richness in marine sediment to be 7.85 × 103 to 6.10 × 105 and 3.28 × 104 to 2.46 × 106 amplicon sequence variants for Archaea and Bacteria, respectively. This richness is comparable to the richness in topsoil and the richness in seawater, indicating that Bacteria are more diverse than Archaea in Earth’s global biosphere.
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Evidence for a Growth Zone for Deep-Subsurface Microbial Clades in Near-Surface Anoxic Sediments. Appl Environ Microbiol 2020; 86:AEM.00877-20. [PMID: 32709727 DOI: 10.1128/aem.00877-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 07/17/2020] [Indexed: 11/20/2022] Open
Abstract
Global marine sediments harbor a large and highly diverse microbial biosphere, but the mechanism by which this biosphere is established during sediment burial is largely unknown. During burial in marine sediments, concentrations of easily metabolized organic compounds and total microbial cell abundance decrease. However, it is unknown whether some microbial clades increase with depth. We show total population increases in 38 microbial families over 3 cm of sediment depth in the upper 7.5 cm of White Oak River (WOR) estuary sediments. Clades that increased with depth were more often associated with one or more of the following: anaerobes, uncultured, or common in deep marine sediments relative to those that decreased. Maximum doubling times (in situ steady-state growth rates could be faster to balance cell decay) were estimated as 2 to 25 years by combining sedimentation rate with either quantitative PCR (qPCR) or the product of the fraction read abundance of 16S rRNA genes and total cell counts (FRAxC). Doubling times were within an order of magnitude of each other in two adjacent cores, as well as in two laboratory enrichments of Cape Lookout Bight (CLB), NC, sediments (average difference of 28% ± 19%). qPCR and FRAxC in sediment cores and laboratory enrichments produced similar doubling times for key deep subsurface uncultured clades Bathyarchaeota (8.7 ± 1.9 years) and Thermoprofundales/MBG-D (4.1 ± 0.7 years). We conclude that common deep subsurface microbial clades experience a narrow zone of growth in shallow sediments, offering an opportunity for selection of long-term subsistence traits after resuspension events.IMPORTANCE Many studies show that the uncultured microbes that dominate global marine sediments do not actually increase in population size as they are buried in marine sediments; rather, they exist in a sort of prolonged torpor for thousands of years. This is because, although studies have shown biomass turnover in these clades, no evidence has ever been found that deeper sediments have larger populations for specific clades than shallower layers. We discovered that they actually do increase population sizes during burial, but only in the upper few centimeters. This suggests that marine sediments may be a vast repository of mostly nongrowing microbes with a thin and relatively rapid area of cell abundance increase in the upper 10 cm, offering a chance for subsurface organisms to undergo natural selection.
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