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Bojar AV, Lécuyer C, Maher W, Bojar HP, Fourel F, Vasile Ş. Multi-element stable isotope geochemistry and arsenic speciation of hydrothermal vent fauna (Alviniconcha sp., Ifremeria nautilei and Eochionelasmus ohtai manusensis), Manus Basin, Papua New Guinea. CHEMOSPHERE 2023; 324:138258. [PMID: 36898438 DOI: 10.1016/j.chemosphere.2023.138258] [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: 01/11/2023] [Revised: 02/21/2023] [Accepted: 02/26/2023] [Indexed: 06/18/2023]
Abstract
Deep-sea hydrothermal vent communities, revealing patterns of niche partitioning, live in a limited area characterised by sharp physico-chemical gradients. In this study, we investigated carbon, sulfur, nitrogen stable isotopes as well as arsenic (As) speciations and concentrations for two snails (Alviniconcha sp. and Ifremeria nautilei) and a crustacean, (Eochionelasmus ohtai manusensis), occupying distinct niches in the hydrothermal vent field of the Vienna Woods, Manus Basin, Western Pacific. δ13C values of Alviniconcha sp. (foot), I. nautilei (foot and chitin) and E. o. manusensis (soft tissue) are similar, from -28 to -33‰ (V-PDB). The δ15N values of Alviniconcha sp. (foot and chitin), I. nautilei (foot and chitin) and E. o. manusensis (soft tissue) range from 8.4 to 10.6‰. The δ34S values of Alviniconcha sp. (foot and chitin), I. nautilei (foot) and E. o. manusensis (soft tissue) range from 5.9 to 11.1‰. Using stable isotopes, for the first time, we inferred a Calvin-Benson (RuBisCo) metabolic pathway for Alviniconcha sp. along with the presence of γ-Proteobacteria symbionts for the Vienna Woods communities. For I. nautilei, a feeding pattern is proposed with γ-Proteobacteria symbiosis and a Calvin-Benson-Bassham diet with mixotrophic feeding. E. ohtai manusensis is filtering bacteria with a CBB feeding strategy, with δ15N values indicating possible higher position in the trophic chain. Arsenic concentrations in the dry tissue of Alviniconcha (foot), I. nautilei (foot) and E. o. manusensis (soft tissue) are high, from 4134 to 8478 μg/g, with inorganic As concentrations of 607, 492 and 104 μg/g, respectively and dimethyl arsenic (DMA) concentrations of 11.12, 0.25 and 11.2 μg/g, respectively. Snails occurring in a vent proximal position have higher As concentration than barnacles, a pattern not observed for S concentrations. Arsenosugars were not put in evidence indicating that the available organic material for the vent organisms are not surface derived.
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Affiliation(s)
- Ana-Voica Bojar
- Department of Environment and Biodiversity, Salzburg University, Hellbrunnerstrasse 34, A-5020, Salzburg, Austria; Department of Mineralogy, Universalmuseum Joanneum, Weinzöttlstrasse 16, A-8045, Graz, Austria; Faculty of Physics, University of Bucharest, 405 Atomiștilor Street, Măgurele 077125, Romania.
| | - Christophe Lécuyer
- Laboratoire de Géologie de Lyon, CNRS UMR 5276, Université Claude Bernard Lyon 1, 69622 Villeurbanne, France; Institut Universitaire de France, 103 Boulevard, Saint-Michel, 75005 Paris, France
| | - William Maher
- Research School of Earth Sciences, Australian National University, Canberra 2000 Australia
| | - Hans-Peter Bojar
- Department of Mineralogy, Universalmuseum Joanneum, Weinzöttlstrasse 16, A-8045, Graz, Austria
| | - François Fourel
- Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés, LEHNA UMR CNRS 5023, Université Claude Bernard Lyon 1, 69622 Villeurbanne, France
| | - Ştefan Vasile
- Department of Geology, Mineralogy, and Paleontology, Faculty of Geology and Geophysics, University of Bucharest, 1 Nicolae Bălcescu Avenue, 010041 Bucharest, Romania
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Lin YT, Xu T, Ip JCH, Sun Y, Fang L, Luan T, Zhang Y, Qian PY, Qiu JW, Qian PY, Qiu JW. Interactions among deep-sea mussels and their epibiotic and endosymbiotic chemoautotrophic bacteria: Insights from multi-omics analysis. Zool Res 2023; 44:106-125. [PMID: 36419378 PMCID: PMC9841196 DOI: 10.24272/j.issn.2095-8137.2022.279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Endosymbiosis with Gammaproteobacteria is fundamental for the success of bathymodioline mussels in deep-sea chemosynthesis-based ecosystems. However, the recent discovery of Campylobacteria on the gill surfaces of these mussels suggests that these host-bacterial relationships may be more complex than previously thought. Using the cold-seep mussel ( Gigantidas haimaensis) as a model, we explored this host-bacterial system by assembling the host transcriptome and genomes of its epibiotic Campylobacteria and endosymbiotic Gammaproteobacteria and quantifying their gene and protein expression levels. We found that the epibiont applies a sulfur oxidizing (SOX) multienzyme complex with the acquisition of soxB from Gammaproteobacteria for energy production and switched from a reductive tricarboxylic acid (rTCA) cycle to a Calvin-Benson-Bassham (CBB) cycle for carbon assimilation. The host provides metabolic intermediates, inorganic carbon, and thiosulfate to satisfy the materials and energy requirements of the epibiont, but whether the epibiont benefits the host is unclear. The endosymbiont adopts methane oxidation and the ribulose monophosphate pathway (RuMP) for energy production, providing the major source of energy for itself and the host. The host obtains most of its nutrients, such as lysine, glutamine, valine, isoleucine, leucine, histidine, and folate, from the endosymbiont. In addition, host pattern recognition receptors, including toll-like receptors, peptidoglycan recognition proteins, and C-type lectins, may participate in bacterial infection, maintenance, and population regulation. Overall, this study provides insights into the complex host-bacterial relationships that have enabled mussels and bacteria to thrive in deep-sea chemosynthetic ecosystems.
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Affiliation(s)
- Yi-Tao Lin
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China
| | - Ting Xu
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China,Department of Ocean Science, Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Jack Chi-Ho Ip
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China
| | - Yanan Sun
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China
| | - Ling Fang
- Instrumental Analysis & Research Center, Sun Yat-Sen University, Guangzhou, Guangdong 510875, China
| | - Tiangang Luan
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou, Guangdong 510875, China,Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou, Guangdong 510006, China
| | - Yu Zhang
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong 518060, China,E-mail:
| | - Pei-Yuan Qian
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China,Department of Ocean Science, Hong Kong University of Science and Technology, Hong Kong SAR, China,
| | - Jian-Wen Qiu
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China,
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Zhou K, Xu Y, Zhang R, Qian PY. Arms race in a cell: genomic, transcriptomic, and proteomic insights into intracellular phage-bacteria interplay in deep-sea snail holobionts. MICROBIOME 2021; 9:182. [PMID: 34479645 PMCID: PMC8418041 DOI: 10.1186/s40168-021-01099-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 05/20/2021] [Indexed: 05/12/2023]
Abstract
BACKGROUND Deep-sea animals in hydrothermal vents often form endosymbioses with chemosynthetic bacteria. Endosymbionts serve essential biochemical and ecological functions, but the prokaryotic viruses (phages) that determine their fate are unknown. RESULTS We conducted metagenomic analysis of a deep-sea vent snail. We assembled four genome bins for Caudovirales phages that had developed dual endosymbiosis with sulphur-oxidising bacteria (SOB) and methane-oxidising bacteria (MOB). Clustered regularly interspaced short palindromic repeat (CRISPR) spacer mapping, genome comparison, and transcriptomic profiling revealed that phages Bin1, Bin2, and Bin4 infected SOB and MOB. The observation of prophages in the snail endosymbionts and expression of the phage integrase gene suggested the presence of lysogenic infection, and the expression of phage structural protein and lysozyme genes indicated active lytic infection. Furthermore, SOB and MOB appear to employ adaptive CRISPR-Cas systems to target phage DNA. Additional expressed defence systems, such as innate restriction-modification systems and dormancy-inducing toxin-antitoxin systems, may co-function and form multiple lines for anti-viral defence. To counter host defence, phages Bin1, Bin2, and Bin3 appear to have evolved anti-restriction mechanisms and expressed methyltransferase genes that potentially counterbalance host restriction activity. In addition, the high-level expression of the auxiliary metabolic genes narGH, which encode nitrate reductase subunits, may promote ATP production, thereby benefiting phage DNA packaging for replication. CONCLUSIONS This study provides new insights into phage-bacteria interplay in intracellular environments of a deep-sea vent snail. Video Abstract.
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Affiliation(s)
- Kun Zhou
- Department of Ocean Science and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Hong Kong University of Science and Technology, Hong Kong, China
- Shenzhen University-HKUST Joint Marine Science Ph.D. Program, Shenzhen University, Shenzhen, 518060, China
| | - Ying Xu
- Shenzhen University-HKUST Joint Marine Science Ph.D. Program, Shenzhen University, Shenzhen, 518060, China.
- Shenzhen Key Laboratory of Marine Bioresource and Eco-environmental Science, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China.
| | - Rui Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University (Xiang'an), Xiamen, Fujian, China.
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519080, China.
| | - Pei-Yuan Qian
- Department of Ocean Science and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Hong Kong University of Science and Technology, Hong Kong, China.
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Sogin EM, Kleiner M, Borowski C, Gruber-Vodicka HR, Dubilier N. Life in the Dark: Phylogenetic and Physiological Diversity of Chemosynthetic Symbioses. Annu Rev Microbiol 2021; 75:695-718. [PMID: 34351792 DOI: 10.1146/annurev-micro-051021-123130] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Possibly the last discovery of a previously unknown major ecosystem on Earth was made just over half a century ago, when researchers found teaming communities of animals flourishing two and a half kilometers below the ocean surface at hydrothermal vents. We now know that these highly productive ecosystems are based on nutritional symbioses between chemosynthetic bacteria and eukaryotes and that these chemosymbioses are ubiquitous in both deep-sea and shallow-water environments. The symbionts are primary producers that gain energy from the oxidation of reduced compounds, such as sulfide and methane, to fix carbon dioxide or methane into biomass to feed their hosts. This review outlines how the symbiotic partners have adapted to living together. We first focus on the phylogenetic and metabolic diversity of these symbioses and then highlight selected research directions that could advance our understanding of the processes that shaped the evolutionary and ecological success of these associations. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- E Maggie Sogin
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany; ,
| | - Manuel Kleiner
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina 27607, USA
| | - Christian Borowski
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany; , .,MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359, Bremen, Germany
| | | | - Nicole Dubilier
- Max Planck Institute for Marine Microbiology, 28359, Bremen, Germany; , .,MARUM-Center for Marine Environmental Sciences, University of Bremen, 28359, Bremen, Germany
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Kuroda M, Nagasaki T, Koito T, Hongo Y, Yoshida T, Maruyama T, Tsuchida S, Nemoto S, Inoue K. Possible Roles of Hypotaurine and Thiotaurine in the Vesicomyid Clam Phreagena okutanii. THE BIOLOGICAL BULLETIN 2021; 240:34-40. [PMID: 33730534 DOI: 10.1086/712396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
AbstractVesicomyid clams, which inhabit deep-sea hydrothermal vents and hydrocarbon seeps, are nutritionally dependent on symbiotic, chemoautotrophic bacteria that produce organic matter by using hydrogen sulfide. Vesicomyid clams absorb hydrogen sulfide from the foot and transport it in their hemolymph to symbionts in the gill. However, mechanisms to cope with hydrogen sulfide toxicity are not fully understood. Previous studies on vent-specific invertebrates, including bathymodiolin mussels, suggest that hypotaurine, a precursor of taurine, mitigates hydrogen sulfide toxicity by binding it to bisulfide ion, so as to synthesize thiotaurine. In this study, we cloned cDNAs from the vesicomyid clam Phreagena okutanii for the taurine transporter that transports hypotaurine into cells and for cysteine dioxygenase and cysteine-sulfinate decarboxylase, major enzymes involved in hypotaurine synthesis. Results of reverse-transcription polymerase chain reaction indicate that mRNAs of these three genes are most abundant in the foot, followed by the gill. However, hypotaurine and thiotaurine levels, measured by reverse-phase high-performance liquid chromatography, were low in the foot and high in the gill. In addition, thiotaurine was detected in hemolymph cells. Hypotaurine synthesized in the foot may be transported to the gill after binding to bisulfide ion, possibly by hemolymph cells.
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Sass K, Güllert S, Streit WR, Perner M. A hydrogen-oxidizing bacterium enriched from the open ocean resembling a symbiont. ENVIRONMENTAL MICROBIOLOGY REPORTS 2020; 12:396-405. [PMID: 32338395 DOI: 10.1111/1758-2229.12847] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 03/31/2020] [Accepted: 04/21/2020] [Indexed: 06/11/2023]
Abstract
A new autotrophic hydrogen-oxidizing Chromatiaceae bacterium, namely bacterium CTD079, was enriched from a water column sample at 1500 m water depth in the southern Pacific Ocean. Based on the phylogeny of 16S rRNA genes, it was closely related to a scaly snail endosymbiont (99.2% DNA sequence identity) whose host so far is only known to colonize hydrothermal vents along the Indian ridge. The average nucleotide identity between the genomes of CTD079 and the snail endosymbiont was 91%. The observed differences likely reflect adaptations to their specific habitats. For example, CTD079 encodes additional enzymes like the formate dehydrogenase increasing the organism's spectrum of energy generation pathways. Other additional physiological features of CTD079 included the increase of viral defence strategies, secretion systems and specific transporters for essential elements. These important genome characteristics suggest an adaptation to life in the open ocean.
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Affiliation(s)
- Katharina Sass
- Molecular Biology of Microbial Consortia, Universität Hamburg, Hamburg, Germany
- Microbiology and Biotechnology, Universität Hamburg, Hamburg, Germany
| | - Simon Güllert
- Microbiology and Biotechnology, Universität Hamburg, Hamburg, Germany
| | - Wolfgang R Streit
- Microbiology and Biotechnology, Universität Hamburg, Hamburg, Germany
| | - Mirjam Perner
- Molecular Biology of Microbial Consortia, Universität Hamburg, Hamburg, Germany
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Wang Y, Liu L, Yu M, Zhou S, Fu T, Sun W, Du R, Zhang XH. Carideicomes alvinocaridis gen. nov., sp. nov., a marine bacterium isolated from shrimp gill in a hydrothermal field of Okinawa Trough. Int J Syst Evol Microbiol 2020; 70:1777-1784. [PMID: 32234113 DOI: 10.1099/ijsem.0.003971] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A Gram-stain-negative, strictly aerobic, oval-shaped, non-motile bacterium with no flagella, designated strain SCR17T, was isolated from a shrimp gill habitat in Tangyin hydrothermal field of Okinawa Trough. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SCR17T formed a lineage within the family 'Rhodobacteraceae', and shared 16S rRNA gene sequence similarity of 93.2-96.2 % to the related genera Aquicoccus and Roseivivax. Strain SCR17T was able to grow with 0-14 % (w/v) NaCl (optimum, 9-10 %). The sole respiratory quinone was ubiquinone-10. The major polar lipids of strain SCR17T comprised phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), an unidentified aminolipid (AL), an unidentified phospholipid (PL) and an unidentified lipid (L). The predominant fatty acids (more than 10 % of the total fatty acids) were C18 : 1ω7c or/and C18 : 1ω6c, anteiso-C15 : 0, C16 : 0 and C19 : 0 cyclo ω8c . The genomic DNA G+C content of strain SCR17T was 67.7 mol%. Based on polyphasic taxonomic analyses, strain SCR17T is considered to represent a novel species in a new genus of the family 'Rhodobacteraceae', for which the name Carideicomes alvinocaridis gen. nov., sp. nov. is proposed. The type strain of Carideicomes alvinocaridis is SCR17T (=JCM 33426T=MCCC 1K03732T). The discovery of a novel host-associated bacterium in hydrothermal fields provides an opportunity for the study of host-bacterial symbiosis in extreme environments.
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Affiliation(s)
- Yiting Wang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Lijun Liu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Min Yu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China.,Laboratory for Marine Ecology and Environmental Science, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266071, PR China.,Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, PR China
| | - Shun Zhou
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Tianyu Fu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Wen Sun
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Rui Du
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
| | - Xiao-Hua Zhang
- Institute of Evolution & Marine Biodiversity, Ocean University of China, Qingdao 266003, PR China.,Laboratory for Marine Ecology and Environmental Science, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266071, PR China.,MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266003, PR China
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Molecular characterization of Bathymodiolus mussels and gill symbionts associated with chemosynthetic habitats from the U.S. Atlantic margin. PLoS One 2019; 14:e0211616. [PMID: 30870419 PMCID: PMC6417655 DOI: 10.1371/journal.pone.0211616] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 01/17/2019] [Indexed: 01/22/2023] Open
Abstract
Mussels of the genus Bathymodiolus are among the most widespread colonizers of hydrothermal vent and cold seep environments, sustained by endosymbiosis with chemosynthetic bacteria. Presumed species of Bathymodiolus are abundant at newly discovered cold seeps on the Mid-Atlantic continental slope, however morphological taxonomy is challenging, and their phylogenetic affinities remain unestablished. Here we used mitochondrial sequence to classify species found at three seep sites (Baltimore Canyon seep (BCS; ~400m); Norfolk Canyon seep (NCS; ~1520m); and Chincoteague Island seep (CTS; ~1000m)). Mitochondrial COI (N = 162) and ND4 (N = 39) data suggest that Bathymodiolus childressi predominates at these sites, although single B. mauritanicus and B. heckerae individuals were detected. As previous work had suggested that methanotrophic and thiotrophic interactions can both occur at a site, and within an individual mussel, we investigated the symbiont communities in gill tissues of a subset of mussels from BCS and NCS. We constructed metabarcode libraries with four different primer sets spanning the 16S gene. A methanotrophic phylotype dominated all gill microbial samples from BCS, but sulfur-oxidizing Campylobacterota were represented by a notable minority of sequences from NCS. The methanotroph phylotype shared a clade with globally distributed Bathymodiolus spp. symbionts from methane seeps and hydrothermal vents. Two distinct Campylobacterota phylotypes were prevalent in NCS samples, one of which shares a clade with Campylobacterota associated with B. childressi from the Gulf of Mexico and the other with Campylobacterota associated with other deep-sea fauna. Variation in chemosynthetic symbiont communities among sites and individuals has important ecological and geochemical implications and suggests shifting reliance on methanotrophy. Continued characterization of symbionts from cold seeps will provide a greater understanding of the ecology of these unique environments as well and their geochemical footprint in elemental cycling and energy flux.
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Takishita K, Takaki Y, Chikaraishi Y, Ikuta T, Ozawa G, Yoshida T, Ohkouchi N, Fujikura K. Genomic Evidence that Methanotrophic Endosymbionts Likely Provide Deep-Sea Bathymodiolus Mussels with a Sterol Intermediate in Cholesterol Biosynthesis. Genome Biol Evol 2017; 9:1148-1160. [PMID: 28453654 PMCID: PMC5421315 DOI: 10.1093/gbe/evx082] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2017] [Indexed: 12/17/2022] Open
Abstract
Sterols are key cyclic triterpenoid lipid components of eukaryotic cellular membranes, which are synthesized through complex multi-enzyme pathways. Similar to most animals, Bathymodiolus mussels, which inhabit deep-sea chemosynthetic ecosystems and harbor methanotrophic and/or thiotrophic bacterial endosymbionts, possess cholesterol as their main sterol. Based on the stable carbon isotope analyses, it has been suggested that host Bathymodiolus mussels synthesize cholesterol using a sterol intermediate derived from the methanotrophic endosymbionts. To test this hypothesis, we sequenced the genome of the methanotrophic endosymbiont in Bathymodiolus platifrons. The genome sequence data demonstrated that the endosymbiont potentially generates up to 4,4-dimethyl-cholesta-8,14,24-trienol, a sterol intermediate in cholesterol biosynthesis, from methane. In addition, transcripts for a subset of the enzymes of the biosynthetic pathway to cholesterol downstream from a sterol intermediate derived from methanotroph endosymbionts were detected in our transcriptome data for B. platifrons. These findings suggest that this mussel can de novo synthesize cholesterol from methane in cooperation with the symbionts. By in situ hybridization analyses, we showed that genes associated with cholesterol biosynthesis from both host and endosymbionts were expressed exclusively in the gill epithelial bacteriocytes containing endosymbionts. Thus, cholesterol production is probably localized within these specialized cells of the gill. Considering that the host mussel cannot de novo synthesize cholesterol and depends largely on endosymbionts for nutrition, the capacity of endosymbionts to synthesize sterols may be important in establishing symbiont–host relationships in these chemosynthetic mussels.
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Affiliation(s)
- Kiyotaka Takishita
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan
| | - Yoshihiro Takaki
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan
| | - Yoshito Chikaraishi
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.,Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan
| | - Tetsuro Ikuta
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan
| | - Genki Ozawa
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.,Department of Marine Biosciences, School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa, Japan
| | - Takao Yoshida
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan
| | - Naohiko Ohkouchi
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan
| | - Katsunori Fujikura
- Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan
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10
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Paul BG, Ding H, Bagby SC, Kellermann MY, Redmond MC, Andersen GL, Valentine DL. Methane-Oxidizing Bacteria Shunt Carbon to Microbial Mats at a Marine Hydrocarbon Seep. Front Microbiol 2017; 8:186. [PMID: 28289403 PMCID: PMC5326789 DOI: 10.3389/fmicb.2017.00186] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 01/25/2017] [Indexed: 01/11/2023] Open
Abstract
The marine subsurface is a reservoir of the greenhouse gas methane. While microorganisms living in water column and seafloor ecosystems are known to be a major sink limiting net methane transport from the marine subsurface to the atmosphere, few studies have assessed the flow of methane-derived carbon through the benthic mat communities that line the seafloor on the continental shelf where methane is emitted. We analyzed the abundance and isotope composition of fatty acids in microbial mats grown in the shallow Coal Oil Point seep field off Santa Barbara, CA, USA, where seep gas is a mixture of methane and CO2. We further used stable isotope probing (SIP) to track methane incorporation into mat biomass. We found evidence that multiple allochthonous substrates supported the rich growth of these mats, with notable contributions from bacterial methanotrophs and sulfur-oxidizers as well as eukaryotic phototrophs. Fatty acids characteristic of methanotrophs were shown to be abundant and 13C-enriched in SIP samples, and DNA-SIP identified members of the methanotrophic family Methylococcaceae as major 13CH4 consumers. Members of Sulfuricurvaceae, Sulfurospirillaceae, and Sulfurovumaceae are implicated in fixation of seep CO2. The mats’ autotrophs support a diverse assemblage of co-occurring bacteria and protozoa, with Methylophaga as key consumers of methane-derived organic matter. This study identifies the taxa contributing to the flow of seep-derived carbon through microbial mat biomass, revealing the bacterial and eukaryotic diversity of these remarkable ecosystems.
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Affiliation(s)
- Blair G Paul
- Department of Earth Science, University of California, Santa Barbara, Santa BarbaraCA, USA; Marine Science Institute, University of California, Santa Barbara, Santa BarbaraCA, USA
| | - Haibing Ding
- Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China Qingdao, China
| | - Sarah C Bagby
- Department of Earth Science, University of California, Santa Barbara, Santa BarbaraCA, USA; Marine Science Institute, University of California, Santa Barbara, Santa BarbaraCA, USA
| | - Matthias Y Kellermann
- Department of Earth Science, University of California, Santa Barbara, Santa BarbaraCA, USA; Marine Science Institute, University of California, Santa Barbara, Santa BarbaraCA, USA
| | - Molly C Redmond
- Department of Earth Science, University of California, Santa Barbara, Santa BarbaraCA, USA; Marine Science Institute, University of California, Santa Barbara, Santa BarbaraCA, USA
| | - Gary L Andersen
- Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley CA, USA
| | - David L Valentine
- Department of Earth Science, University of California, Santa Barbara, Santa BarbaraCA, USA; Marine Science Institute, University of California, Santa Barbara, Santa BarbaraCA, USA
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Hestetun JT, Dahle H, Jørgensen SL, Olsen BR, Rapp HT. The Microbiome and Occurrence of Methanotrophy in Carnivorous Sponges. Front Microbiol 2016; 7:1781. [PMID: 27881974 PMCID: PMC5101230 DOI: 10.3389/fmicb.2016.01781] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/24/2016] [Indexed: 12/03/2022] Open
Abstract
As shown by recent studies, filter-feeding sponges are known to host a wide variety of microorganisms. However, the microbial community of the non-filtering carnivorous sponges (Porifera, Cladorhizidae) has been the subject of less scrutiny. Here, we present the results from a comparative study of the methanotrophic carnivorous sponge Cladorhiza methanophila from a mud volcano-rich area at the Barbados Accretionary Prism, and five carnivorous species from the Jan Mayen Vent Field (JMVF) at the Arctic Mid-Ocean Ridge. Results from 16S rRNA microbiome data indicate the presence of a diverse assemblage of associated microorganisms in carnivorous sponges mainly from the Gamma- and Alphaproteobacteria, Flavobacteriaceae, and Thaumarchaeota. While the abundance of particular groups varied throughout the dataset, we found interesting similarities to previous microbiome results from non-carnivorous deep sea sponges, suggesting that the carnivorous sponges share characteristics of a previously hypothesized putative deep-sea sponge microbial community. Chemolithoautotrophic symbiosis was confirmed for C. methanophila through a microbial community with a high abundance of Methylococcales and very light isotopic δ13C and δ15N ratios (-60 to -66‰/3.5 to 5.2‰) compared to the other cladorhizid species (-22 to -24‰/8.5 to 10.5‰). We provide evidence for the presence of putative sulfur-oxidizing Gammaproteobacteria in the arctic cladorhizids; however, δ13C and δ15N signatures did not provide evidence for significant chemoautotrophic symbiosis in this case, and the slightly higher abundance of cladorhizids at the JMVF site compared to the nearby deep sea likely stem from an increased abundance of prey rather than a more direct vent association. The phylogenetic position of C. methanophila in relation to other carnivorous sponges was established using a three-gene phylogenetic analysis, and it was found to be closely related to other non-methanotrophic Cladorhiza species with a similar morphology included in the dataset, suggesting a recent origin for methanotrophy in this species. C. methanophila remains the only known carnivorous sponge with a strong, chemolithoautotrophic symbiont association, and methanotrophic symbiosis does not seem to be a widespread property within the Cladorhizidae.
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Affiliation(s)
- Jon T. Hestetun
- Marine Biodiversity Group, Department of Biology, University of BergenBergen, Norway
- Centre for Geobiology, University of BergenBergen, Norway
| | - Håkon Dahle
- Centre for Geobiology, University of BergenBergen, Norway
| | | | - Bernt R. Olsen
- Marine Biodiversity Group, Department of Biology, University of BergenBergen, Norway
- Centre for Geobiology, University of BergenBergen, Norway
| | - Hans T. Rapp
- Marine Biodiversity Group, Department of Biology, University of BergenBergen, Norway
- Centre for Geobiology, University of BergenBergen, Norway
- Uni Research Environment, Uni Research ASBergen, Norway
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Sun QL, Zeng ZG, Chen S, Sun L. First Comparative Analysis of the Community Structures and Carbon Metabolic Pathways of the Bacteria Associated with Alvinocaris longirostris in a Hydrothermal Vent of Okinawa Trough. PLoS One 2016; 11:e0154359. [PMID: 27111851 PMCID: PMC4844111 DOI: 10.1371/journal.pone.0154359] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 04/12/2016] [Indexed: 11/19/2022] Open
Abstract
Alvinocaris longirostris is a species of shrimp existing in the hydrothermal fields of Okinawa Trough. To date the structure and function of the microbial community associated with A. longirostris are essentially unknown. In this study, by employment of the techniques of high through-put sequencing and clone library construction and analysis, we compared for the first time the community structures and metabolic profiles of microbes associated with the gill and gut of A. longirostris in a hydrothermal field of Okinawa Trough. Fourteen phyla were detected in the gill and gut communities, of which 11 phyla were shared by both tissues. Proteobacteria made up a substantial proportion in both tissues, while Firmicutes was abundant only in gut. Although gill and gut communities were similar in bacterial diversities, the bacterial community structures in these two tissues were significantly different. Further, we discovered for the first time the existence in the gill and gut communities of A. longirostris the genes (cbbM and aclB) encoding the key enzymes of Calvin-Benson-Bassham (CBB) cycle and the reductive tricarboxylic acid (rTCA) cycle, and that both cbbM and aclB were significantly more abundant in gill than in gut. Taken together, these results provide the first evidence that at least two carbon fixation pathways are present in both the gill and the gut communities of A. longirostris, and that the communities in different tissues likely differ in autotrophic productivity.
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Affiliation(s)
- Qing-lei Sun
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhi-gang Zeng
- Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Shuai Chen
- Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
| | - Li Sun
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
- * E-mail:
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Detree C, Chabenat A, Lallier FH, Satoh N, Shoguchi E, Tanguy A, Mary J. Multiple I-Type Lysozymes in the Hydrothermal Vent Mussel Bathymodiolus azoricus and Their Role in Symbiotic Plasticity. PLoS One 2016; 11:e0148988. [PMID: 26882089 PMCID: PMC4755537 DOI: 10.1371/journal.pone.0148988] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 01/26/2016] [Indexed: 11/18/2022] Open
Abstract
The aim of this study was first to identify lysozymes paralogs in the deep sea mussel Bathymodiolus azoricus then to measure their relative expression or activity in different tissue or conditions. B. azoricus is a bivalve that lives close to hydrothermal chimney in the Mid-Atlantic Ridge (MAR). They harbour in specialized gill cells two types of endosymbiont (gram-bacteria): sulphide oxidizing bacteria (SOX) and methanotrophic bacteria (MOX). This association is thought to be ruled by specific mechanism or actors of regulation to deal with the presence of symbiont but these mechanisms are still poorly understood. Here, we focused on the implication of lysozyme, a bactericidal enzyme, in this endosymbiosis. The relative expression of Ba-lysozymes paralogs and the global anti-microbial activity, were measured in natural population (Lucky Strike--1700 m, Mid-Atlantic Ridge), and in in situ experimental conditions. B. azoricus individuals were moved away from the hydrothermal fluid to induce a loss of symbiont. Then after 6 days some mussels were brought back to the mussel bed to induce a re-acquisition of symbiotic bacteria. Results show the presence of 6 paralogs in B. azoricus. In absence of symbionts, 3 paralogs are up-regulated while others are not differentially expressed. Moreover the global activity of lysozyme is increasing with the loss of symbiont. All together these results suggest that lysozyme may play a crucial role in symbiont regulation.
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Affiliation(s)
- Camille Detree
- Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7144, Adaptation et Diversité en Milieu Marin, Equipe ABICE, Station Biologique de Roscoff, 29680 Roscoff, France
| | - Apolline Chabenat
- Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7144, Adaptation et Diversité en Milieu Marin, Equipe ABICE, Station Biologique de Roscoff, 29680 Roscoff, France
| | - François H. Lallier
- Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7144, Adaptation et Diversité en Milieu Marin, Equipe ABICE, Station Biologique de Roscoff, 29680 Roscoff, France
| | - Nori Satoh
- Marine Genomics Unit, Okinawa Institute of Science and Technology, Onna, Japan
| | - Eiichi Shoguchi
- Marine Genomics Unit, Okinawa Institute of Science and Technology, Onna, Japan
| | - Arnaud Tanguy
- Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7144, Adaptation et Diversité en Milieu Marin, Equipe ABICE, Station Biologique de Roscoff, 29680 Roscoff, France
| | - Jean Mary
- Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7144, Adaptation et Diversité en Milieu Marin, Equipe ABICE, Station Biologique de Roscoff, 29680 Roscoff, France
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Molecular evidence of digestion and absorption of epibiotic bacterial community by deep-sea crab Shinkaia crosnieri. ISME JOURNAL 2015; 9:821-31. [PMID: 25314318 DOI: 10.1038/ismej.2014.178] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 08/28/2014] [Accepted: 08/30/2014] [Indexed: 11/08/2022]
Abstract
The hydrothermal vent crab Shinkaia crosnieri is considered to obtain nutrition from the epibiotic bacteria found on the setae, but previous studies have not shown how nutrients can be transferred from the epibionts to the host. In this study, microscopic observations of S. crosnieri intestinal components detected autofluorescent setae fragments and pigmentation derived from the digestion of epibionts in a dye-stained epibiont tracer experiment. An in vitro digestion experiment with epibiotic populations using an intestinal extract demonstrated the degradation of epibiotic cells by digestive enzymes. A phylogenetic analysis showed that many of the bacterial 16S ribosomal RNA gene sequences obtained from the intestine were closely related to the sequences of the epibionts, thus they were probably derived from the epibionts. A stable isotope tracer experiment also indicated that (13)C assimilated by the epibionts provided a carbon (nutrition) source for the host. Both activity measurements and isotope studies showed that chemosynthetic metabolism by the gut microbial components were inactive. Together with the feeding behaviour of living S. crosnieri, these results indicate that S. crosnieri ingests the epibionts using maxillipeds and assimilates them via its digestive organs as a nutrient source. The results of this study elucidate the mechanism of nutritional transfer in ectosymbiosis between chemosynthetic bacteria and deep-sea invertebrates.
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Meena KK, Kumar M, Mishra S, Ojha SK, Wakchaure GC, Sarkar B. Phylogenetic study of methanol oxidizers from chilika-lake sediments using genomic and metagenomic approaches. Indian J Microbiol 2015; 55:151-62. [PMID: 25805901 DOI: 10.1007/s12088-015-0510-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 01/03/2015] [Indexed: 01/13/2023] Open
Abstract
Group-wise diversity of sediment methylotrophs of Chilika lake (Lat. 19°28'-19°54'N; Long. 85°06'-85°35'E) Odisha, India at various identified sites was studied. Both the culturable and unculturable (metagenome) methylotrophs were investigated in the lake sediments employing both mxaF and 16S rRNA genes as markers. ARDRA profiling, 16S rRNA gene sequencing, PAGE profiling of HaeIII, EcoRI restricted mxaF gene and the mxaF gene sequences using culture-dependent approach revealed the relatedness of α-proteobacteria and Methylobacterium, Hyphomicrobium and Ancyclobacter sp. The total viable counts of the culturable aerobic methylotrophs were relatively higher in sediments near the sea mouth (S3; Panaspada), also demonstrated relatively high salinity (0.1 M NaCl) tolerance. Metagenomic DNA from the sediments, amplified using GC clamp mxaF primers and resolved through DGGE, revealed the diversity within the unculturable methylotrophic bacterium Methylobacterium organophilum, Ancyclobacter aquaticus, Burkholderiales and Hyphomicrobium sp. Culture-independent analyses revealed that up to 90 % of the methylotrophs were unculturable. The study enhances the general understandings of the metagenomic methylotrophs from such a special ecological niche.
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Affiliation(s)
- Kamlesh K Meena
- National Bureau of Agriculturally Important Microorganisms, Mau Nath Bhanjan, 275 101 UP India ; National Institute of Abiotic Stress Management, Malegaon, Baramati, Pune, Maharashtra India
| | - Manish Kumar
- National Bureau of Agriculturally Important Microorganisms, Mau Nath Bhanjan, 275 101 UP India
| | - Snehasish Mishra
- School of Biotechnology, KIIT University, Campus-11, Bhubaneswar, 751024 Odisha India
| | - Sanjay Kumar Ojha
- School of Biotechnology, KIIT University, Campus-11, Bhubaneswar, 751024 Odisha India
| | - Goraksha C Wakchaure
- National Institute of Abiotic Stress Management, Baramati, Pune, 413115 Maharashtra India
| | - Biplab Sarkar
- National Institute of Abiotic Stress Management, Baramati, Pune, 413115 Maharashtra India
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16
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Characterization of Bacterial Symbionts in Deep-Sea Fauna: Protocols for Sample Conditioning, Fluorescence In Situ Hybridization, and Image Analysis. SPRINGER PROTOCOLS HANDBOOKS 2015. [DOI: 10.1007/8623_2015_73] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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17
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Elisabeth NH, Caro A, Césaire T, Mansot JL, Escalas A, Sylvestre MN, Jean-Louis P, Gros O. Comparative modifications in bacterial gill-endosymbiotic populations of the two bivalves Codakia orbiculata and Lucina pensylvanica during bacterial loss and reacquisition. FEMS Microbiol Ecol 2014; 89:646-58. [PMID: 24939560 DOI: 10.1111/1574-6941.12366] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 05/21/2014] [Accepted: 06/05/2014] [Indexed: 11/27/2022] Open
Abstract
Until now, the culture of sulphur-oxidizing bacterial symbionts associated with marine invertebrates remains impossible. Therefore, few studies focused on symbiont's physiology under stress conditions. In this study, we carried out a comparative experiment based on two different species of lucinid bivalves (Codakia orbiculata and Lucina pensylvanica) under comparable stress factors. The bivalves were starved for 6 months in sulphide-free filtered seawater. For C. orbiculata only, starved individuals were then put back to the field, in natural sediment. We used in situ hybridization, flow cytometry and X-ray fluorescence to characterize the symbiont population hosted in the gills of both species. In L. pensylvanica, no decrease in symbiont abundance was observed throughout the starvation experiment, whereas elemental sulphur slowly decreased to zero after 3 months of starvation. Conversely, in C. orbiculata, symbiont abundance within bacteriocytes decreased rapidly and sulphur from symbionts disappeared during the first weeks of the experiment. The modifications of the cellular characteristics (SSC--relative cell size and FL1--genomic content) of the symbiotic populations along starvation were not comparable between species. Return to the sediment of starved C. orbiculata individuals led to a rapid (2-4 weeks) recovery of symbiotic cellular characteristics, comparable with unstressed symbionts. These results suggest that endosymbiotic population regulation is host-species-dependent in lucinids.
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Affiliation(s)
- Nathalie H Elisabeth
- UMR 7138 UPMC-CNRS, Equipe "Biologie de la Mangrove", Département de Biologie, UFR des Sciences Exactes et Naturelles, Université des Antilles et de la Guyane, Pointe-à-Pitre Cedex, Guadeloupe, France
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18
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Cole C, Coelho AV, James RH, Connelly D, Sheehan D. Proteomic responses to metal-induced oxidative stress in hydrothermal vent-living mussels, Bathymodiolus sp., on the Southwest Indian Ridge. MARINE ENVIRONMENTAL RESEARCH 2014; 96:29-37. [PMID: 24080408 DOI: 10.1016/j.marenvres.2013.09.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/03/2013] [Accepted: 09/09/2013] [Indexed: 06/02/2023]
Abstract
Bathymodiolin mussels are amongst the dominant fauna occupying hydrothermal vent ecosystems throughout the World's oceans. This subfamily inhabits a highly ephemeral and variable environment, where exceptionally high concentrations of reduced sulphur species and heavy metals necessitate adaptation of specialised detoxification mechanisms. Whilst cellular responses to common anthropogenic pollutants are well-studied in shallow-water species, they remain limited in deep-sea vent fauna. Bathymodiolus sp. were sampled from two newly-discovered vent sites on the Southwest Indian Ridge (Tiamat and Knuckers Gaff) by the remotely operated vehicle (ROV) Kiel 6000 during the RRS James Cook cruise, JC 067 in November 2011. Here, we use redox proteomics to investigate the effects of tissue metal accumulation on protein expression and thiol oxidation in gill. Following 2D PAGE, we demonstrate a significant difference in intensity in 30 protein spots in this organ between the two vent sites out of 205 matched spots. We also see significant variations in thiol oxidation in 15 spots, out of 143 matched. At Tiamat, 23 protein spots are up-regulated compared to Knuckers Gaff and we identify 5 of these with important roles in metabolism, cell structure, stress response, and redox homeostasis. We suggest that increased metal exposure triggers changes in the proteome, regulating tissue uptake. This is evident both between vent sites and across a chemical gradient within the Knuckers Gaff vent site. Our findings highlight the importance of proteomic plasticity in successful adaptation to the spatially and temporally fluctuating chemical environments that are characteristic of hydrothermal vent habitats.
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Affiliation(s)
- Catherine Cole
- Department of Ocean and Earth Science, University of Southampton, European Way, Waterfront Campus, Southampton SO14 3ZH, UK.
| | - Ana Varela Coelho
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Rachael H James
- National Oceanography Centre, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK
| | - Doug Connelly
- National Oceanography Centre, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK
| | - David Sheehan
- School of Biochemistry and Cell Biology, Environmental Research Institute, University College Cork, Ireland
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Becker EL, Cordes EE, Macko SA, Lee RW, Fisher CR. Using stable isotope compositions of animal tissues to infer trophic interactions in Gulf of Mexico lower slope seep communities. PLoS One 2013; 8:e74459. [PMID: 24324572 PMCID: PMC3855623 DOI: 10.1371/journal.pone.0074459] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 07/31/2013] [Indexed: 11/25/2022] Open
Abstract
We analyzed the tissue carbon, nitrogen, and sulfur stable isotope contents of macrofaunal communities associated with vestimentiferan tubeworms and bathymodiolin mussels from the Gulf of Mexico lower continental slope (970-2800 m). Shrimp in the genus Alvinocaris associated with vestimentiferans from shallow (530 m) and deep (1400-2800 m) sites were used to test the hypothesis that seep animals derive a greater proportion of their nutrition from seeps (i.e. a lower proportion from the surface) at greater depths. To account for spatial variability in the inorganic source pool, we used the differences between the mean tissue δ13C and δ15N of the shrimp in each collection and the mean δ 13C and δ15N values of the vestimentiferans from the same collection, since vestimentiferans are functionally autotrophic and serve as a baseline for environmental isotopic variation. There was a significant negative relationship between this difference and depth for both δ13C and δ15N (p=0.02 and 0.007, respectively), which supports the hypothesis of higher dependence on seep nutrition with depth. The small polychaete worm Protomystides sp. was hypothesized to be a blood parasite of the vestimentiferan Escarpialaminata. There was a highly significant linear relationship between the δ13C values of Protomystides sp. and the E. laminata individuals to which they were attached across all collections (p < 0.001) and within a single collection (p = 0.01), although this relationship was not significant for δ15N and δ34S. We made several other qualitative inferences with respect to the feeding biology of the taxa occurring in these lower slope seeps, some of which have not been described prior to this study.
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Affiliation(s)
- Erin L. Becker
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail:
| | - Erik E. Cordes
- Biology Department, Temple University, Philadelphia, Pennsylvania, United States of America
| | - Stephen A. Macko
- Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia, United States of America
| | - Raymond W. Lee
- School of Biological Sciences, Washington State University, Pullman, Washington, United States of America
| | - Charles R. Fisher
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
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20
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Exploration and prediction of interactions between methanotrophs and heterotrophs. Res Microbiol 2013; 164:1045-54. [DOI: 10.1016/j.resmic.2013.08.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 08/27/2013] [Indexed: 01/28/2023]
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21
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Sulfur oxidizers dominate carbon fixation at a biogeochemical hot spot in the dark ocean. ISME JOURNAL 2013; 7:2349-60. [PMID: 23842654 DOI: 10.1038/ismej.2013.113] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 05/25/2013] [Accepted: 05/31/2013] [Indexed: 11/09/2022]
Abstract
Bacteria and archaea in the dark ocean (>200 m) comprise 0.3-1.3 billion tons of actively cycled marine carbon. Many of these microorganisms have the genetic potential to fix inorganic carbon (autotrophs) or assimilate single-carbon compounds (methylotrophs). We identified the functions of autotrophic and methylotrophic microorganisms in a vent plume at Axial Seamount, where hydrothermal activity provides a biogeochemical hot spot for carbon fixation in the dark ocean. Free-living members of the SUP05/Arctic96BD-19 clade of marine gamma-proteobacterial sulfur oxidizers (GSOs) are distributed throughout the northeastern Pacific Ocean and dominated hydrothermal plume waters at Axial Seamount. Marine GSOs expressed proteins for sulfur oxidation (adenosine phosphosulfate reductase, sox (sulfur oxidizing system), dissimilatory sulfite reductase and ATP sulfurylase), carbon fixation (ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO)), aerobic respiration (cytochrome c oxidase) and nitrogen regulation (PII). Methylotrophs and iron oxidizers were also active in plume waters and expressed key proteins for methane oxidation and inorganic carbon fixation (particulate methane monooxygenase/methanol dehydrogenase and RuBisCO, respectively). Proteomic data suggest that free-living sulfur oxidizers and methylotrophs are among the dominant primary producers in vent plume waters in the northeastern Pacific Ocean.
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22
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Toward an Appreciation of Hydrothennal-Vent Animals: Their Environment, Physiological Ecology, and Tissue Stable Isotope Values. ACTA ACUST UNITED AC 2013. [DOI: 10.1029/gm091p0297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
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23
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Mills CT, Slater GF, Dias RF, Carr SA, Reddy CM, Schmidt R, Mandernack KW. The relative contribution of methanotrophs to microbial communities and carbon cycling in soil overlying a coal-bed methane seep. FEMS Microbiol Ecol 2013; 84:474-94. [PMID: 23346979 DOI: 10.1111/1574-6941.12079] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 01/17/2013] [Accepted: 01/18/2013] [Indexed: 11/30/2022] Open
Abstract
Seepage of coal-bed methane (CBM) through soils is a potential source of atmospheric CH4 and also a likely source of ancient (i.e. (14) C-dead) carbon to soil microbial communities. Natural abundance (13) C and (14) C compositions of bacterial membrane phospholipid fatty acids (PLFAs) and soil gas CO2 and CH4 were used to assess the incorporation of CBM-derived carbon into methanotrophs and other members of the soil microbial community. Concentrations of type I and type II methanotroph PLFA biomarkers (16:1ω8c and 18:1ω8c, respectively) were elevated in CBM-impacted soils compared with a control site. Comparison of PLFA and 16s rDNA data suggested type I and II methanotroph populations were well estimated and overestimated by their PLFA biomarkers, respectively. The δ(13) C values of PLFAs common in type I and II methanotrophs were as negative as -67‰ and consistent with the assimilation of CBM. PLFAs more indicative of nonmethanotrophic bacteria had δ(13) C values that were intermediate indicating assimilation of both plant- and CBM-derived carbon. Δ(14) C values of select PLFAs (-351 to -936‰) indicated similar patterns of CBM assimilation by methanotrophs and nonmethanotrophs and were used to estimate that 35-91% of carbon assimilated by nonmethanotrophs was derived from CBM depending on time of sampling and soil depth.
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Affiliation(s)
- Christopher T Mills
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO, USA
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Roeselers G, Newton ILG. On the evolutionary ecology of symbioses between chemosynthetic bacteria and bivalves. Appl Microbiol Biotechnol 2012; 94:1-10. [PMID: 22354364 PMCID: PMC3304057 DOI: 10.1007/s00253-011-3819-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 12/03/2011] [Accepted: 12/05/2011] [Indexed: 11/28/2022]
Abstract
Mutualistic associations between bacteria and eukaryotes occur ubiquitously in nature, forming the basis for key ecological and evolutionary innovations. Some of the most prominent examples of these symbioses are chemosynthetic bacteria and marine invertebrates living in the absence of sunlight at deep-sea hydrothermal vents and in sediments rich in reduced sulfur compounds. Here, chemosynthetic bacteria living in close association with their hosts convert CO2 or CH4 into organic compounds and provide the host with necessary nutrients. The dominant macrofauna of hydrothermal vent and cold seep ecosystems all depend on the metabolic activity of chemosynthetic bacteria, which accounts for almost all primary production in these complex ecosystems. Many of these enigmatic mutualistic associations are found within the molluscan class Bivalvia. Currently, chemosynthetic symbioses have been reported from five distinct bivalve families (Lucinidae, Mytilidae, Solemyidae, Thyasiridae, and Vesicomyidae). This brief review aims to provide an overview of the diverse physiological and genetic adaptations of symbiotic chemosynthetic bacteria and their bivalve hosts.
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Affiliation(s)
- Guus Roeselers
- Microbiology and Systems Biology Group, TNO, Utrechtseweg 48, 3700 AJ Zeist, The Netherlands.
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Boutet I, Ripp R, Lecompte O, Dossat C, Corre E, Tanguy A, Lallier FH. Conjugating effects of symbionts and environmental factors on gene expression in deep-sea hydrothermal vent mussels. BMC Genomics 2011; 12:530. [PMID: 22034982 PMCID: PMC3218092 DOI: 10.1186/1471-2164-12-530] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 10/28/2011] [Indexed: 11/17/2022] Open
Abstract
Background The deep-sea hydrothermal vent mussel Bathymodiolus azoricus harbors thiotrophic and methanotrophic symbiotic bacteria in its gills. While the symbiotic relationship between this hydrothermal mussel and these chemoautotrophic bacteria has been described, the molecular processes involved in the cross-talking between symbionts and host, in the maintenance of the symbiois, in the influence of environmental parameters on gene expression, and in transcriptome variation across individuals remain poorly understood. In an attempt to understand how, and to what extent, this double symbiosis affects host gene expression, we used a transcriptomic approach to identify genes potentially regulated by symbiont characteristics, environmental conditions or both. This study was done on mussels from two contrasting populations. Results Subtractive libraries allowed the identification of about 1000 genes putatively regulated by symbiosis and/or environmental factors. Microarray analysis showed that 120 genes (3.5% of all genes) were differentially expressed between the Menez Gwen (MG) and Rainbow (Rb) vent fields. The total number of regulated genes in mussels harboring a high versus a low symbiont content did not differ significantly. With regard to the impact of symbiont content, only 1% of all genes were regulated by thiotrophic (SOX) and methanotrophic (MOX) bacteria content in MG mussels whereas 5.6% were regulated in mussels collected at Rb. MOX symbionts also impacted a higher proportion of genes than SOX in both vent fields. When host transcriptome expression was analyzed with respect to symbiont gene expression, it was related to symbiont quantity in each field. Conclusions Our study has produced a preliminary description of a transcriptomic response in a hydrothermal vent mussel host of both thiotrophic and methanotrophic symbiotic bacteria. This model can help to identify genes involved in the maintenance of symbiosis or regulated by environmental parameters. Our results provide evidence of symbiont effect on transcriptome regulation, with differences related to type of symbiont, even though the relative percentage of genes involved remains limited. Differences observed between the vent site indicate that environment strongly influences transcriptome regulation and impacts both activity and relative abundance of each symbiont. Among all these genes, those participating in recognition, the immune system, oxidative stress, and energy metabolism constitute new promising targets for extended studies on symbiosis and the effect of environmental parameters on the symbiotic relationships in B. azoricus.
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Affiliation(s)
- Isabelle Boutet
- CNRS, UMR 7144, Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, 29682 Roscoff, France.
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Hydrogen is an energy source for hydrothermal vent symbioses. Nature 2011; 476:176-80. [PMID: 21833083 DOI: 10.1038/nature10325] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 06/20/2011] [Indexed: 11/08/2022]
Abstract
The discovery of deep-sea hydrothermal vents in 1977 revolutionized our understanding of the energy sources that fuel primary productivity on Earth. Hydrothermal vent ecosystems are dominated by animals that live in symbiosis with chemosynthetic bacteria. So far, only two energy sources have been shown to power chemosynthetic symbioses: reduced sulphur compounds and methane. Using metagenome sequencing, single-gene fluorescence in situ hybridization, immunohistochemistry, shipboard incubations and in situ mass spectrometry, we show here that the symbionts of the hydrothermal vent mussel Bathymodiolus from the Mid-Atlantic Ridge use hydrogen to power primary production. In addition, we show that the symbionts of Bathymodiolus mussels from Pacific vents have hupL, the key gene for hydrogen oxidation. Furthermore, the symbionts of other vent animals such as the tubeworm Riftia pachyptila and the shrimp Rimicaris exoculata also have hupL. We propose that the ability to use hydrogen as an energy source is widespread in hydrothermal vent symbioses, particularly at sites where hydrogen is abundant.
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Direct image-based correlative microscopy technique for coupling identification and structural investigation of bacterial symbionts associated with metazoans. Appl Environ Microbiol 2011; 77:4172-9. [PMID: 21515722 DOI: 10.1128/aem.02461-10] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Coupling prokaryote identification with ultrastructural investigation of bacterial communities has proven difficult in environmental samples. Prokaryotes can be identified by using specific probes and fluorescence in situ hybridization (FISH), but resolution achieved by light microscopes does not allow ultrastructural investigation. In the case of symbioses involving bacteria associated with metazoan tissues, FISH-based studies often indicate the co-occurrence of several bacterial types within a single host species. The ultrastructure is then relevant to address host and bacterial morphology and the intra- or extracellular localization of symbionts. A simple protocol for correlative light and electron microscopy (CLEM) is presented here which allows FISH-based identification of specific 16S rRNA phylotypes and transmission electron microscopy to be performed on a same sample. Image analysis tools are provided to superimpose images obtained and generate overlays. This procedure has been applied to two symbiont-bearing metazoans, namely, aphids and deep-sea mussels. The FISH protocol was modified to take into account constraints associated with the use of electron microscopy grids, and intense and specific signals were obtained. FISH signals were successfully overlaid with bacterial morphotypes in aphids. We thus used the method to address the question of symbiont morphology and localization in a deep-sea mussel. Signals from a type I methanotroph-related phylotype were associated with morphotypes displaying the stacked internal membranes typical for this group and three-dimensional electron tomography was performed, confirming for the first time the correspondence between morphology and phylotype. CLEM is thus feasible and reliable and could emerge as a potent tool for the study of prokaryotic communities.
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Childress JJ, Girguis PR. The metabolic demands of endosymbiotic chemoautotrophic metabolism on host physiological capacities. ACTA ACUST UNITED AC 2011; 214:312-25. [PMID: 21177951 DOI: 10.1242/jeb.049023] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
While chemoautotrophic endosymbioses of hydrothermal vents and other reducing environments have been well studied, little attention has been paid to the magnitude of the metabolic demands placed upon the host by symbiont metabolism and the adaptations necessary to meet such demands. Here we make the first attempt at such an evaluation, and show that moderate to high rates of chemoautotrophic or methanotrophic metabolism impose oxygen uptake and proton equivalent elimination demands upon the hosts that are much higher than is typical for the non-symbiotic annelid, bivalve and gastropod lineages to which they are related. The properties of the hosts are described and compared to determine which properties are associated with and predictive of the highest rates. We suggest that the high oxygen demand of these symbionts is perhaps the most limiting flux for the symbioses. Among the consequences of such demands has been the widespread presence of circulating and/or tissue hemoglobins in these symbioses that are necessary to support high metabolic rates in thioautotrophic endosymbioses. We also compare photoautotrophic with chemoautotrophic and methanotrophic endosymbioses to evaluate the differences and similarities in physiologies. These analyses suggest that the high demand for oxygen by chemoautotrophic and methanotrophic symbionts is likely a major factor precluding their endosymbiosis with cnidarians.
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Affiliation(s)
- J J Childress
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA.
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Extracellular and mixotrophic symbiosis in the whale-fall mussel Adipicola pacifica: a trend in evolution from extra- to intracellular symbiosis. PLoS One 2010; 5:e11808. [PMID: 20676405 PMCID: PMC2910738 DOI: 10.1371/journal.pone.0011808] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2009] [Accepted: 06/24/2010] [Indexed: 11/19/2022] Open
Abstract
Background Deep-sea mussels harboring chemoautotrophic symbionts from hydrothermal vents and seeps are assumed to have evolved from shallow-water asymbiotic relatives by way of biogenic reducing environments such as sunken wood and whale falls. Such symbiotic associations have been well characterized in mussels collected from vents, seeps and sunken wood but in only a few from whale falls. Methodology/Principal Finding Here we report symbioses in the gill tissues of two mussels, Adipicola crypta and Adipicola pacifica, collected from whale-falls on the continental shelf in the northwestern Pacific. The molecular, morphological and stable isotopic characteristics of bacterial symbionts were analyzed. A single phylotype of thioautotrophic bacteria was found in A. crypta gill tissue and two distinct phylotypes of bacteria (referred to as Symbiont A and Symbiont C) in A. pacifica. Symbiont A and the A. crypta symbiont were affiliated with thioautotrophic symbionts of bathymodiolin mussels from deep-sea reducing environments, while Symbiont C was closely related to free-living heterotrophic bacteria. The symbionts in A. crypta were intracellular within epithelial cells of the apical region of the gills and were extracellular in A. pacifica. No spatial partitioning was observed between the two phylotypes in A. pacifica in fluorescence in situ hybridization experiments. Stable isotopic analyses of carbon and sulfur indicated the chemoautotrophic nature of A. crypta and mixotrophic nature of A. pacifica. Molecular phylogenetic analyses of the host mussels showed that A. crypta constituted a monophyletic clade with other intracellular symbiotic (endosymbiotic) mussels and that A. pacifica was the sister group of all endosymbiotic mussels. Conclusions/Significance These results strongly suggest that the symbiosis in A. pacifica is at an earlier stage in evolution than other endosymbiotic mussels. Whale falls and other modern biogenic reducing environments may act as refugia for primal chemoautotrophic symbioses between eukaryotes and prokaryotes since the extinction of ancient large marine vertebrates.
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Pond DW, Bell MV, Dixon DR, Fallick AE, Segonzac M, Sargent JR. Stable-carbon-isotope composition of Fatty acids in hydrothermal vent mussels containing methanotrophic and thiotrophic bacterial endosymbionts. Appl Environ Microbiol 2010; 64:370-5. [PMID: 16349492 PMCID: PMC124722 DOI: 10.1128/aem.64.1.370-375.1998] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fatty acid biomarker analysis coupled with gas chromatography-isotope ratio mass spectrometry was used to confirm the presence of methanotrophic and thiotrophic bacterial endosymbionts in the tissues of a hydrothermal vent mussel (Bathymodiolus sp.), collected from the Menez Gwen vent field on the mid-Atlantic ridge. Monounsaturated (n-8) fatty acids, which are diagnostic of methanotrophic bacteria, were detected in all three types of tissues examined (gill, posterior adductor, and mantle), although levels were highest in gill tissues where the bacteria were found. Stable-carbon-isotope compositions (delta-C per mille relative to that of Peedee belemnite) of fatty acids for all three tissues ranged from -24.9 to -34.9 per thousand, which encompasses the range predicted for both thiotroph- and methanotroph-based nutrition. The data suggest that these thio- and methanotrophic bacterial endosymbionts are equally important in the nutrition of the vent mussel at this particular vent site.
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Affiliation(s)
- D W Pond
- NERC Unit of Aquatic Biochemistry, Department of Biological and Molecular Sciences, University of Stirling, Stirling FK9 4LA, Plymouth Marine Laboratory, Plymouth PL1 3DH, and Isotope Geosciences Unit, SURRC, East Kilbride, Glasgow G75 OQF, United Kingdom, and IFREMER, F-29280 Plouzané, Brest, France
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Brooks JM, Kennicutt MC, Fisher CR, Macko SA, Cole K, Childress JJ, Bidigare RR, Vetter RD. Deep-sea hydrocarbon seep communities: evidence for energy and nutritional carbon sources. Science 2010; 238:1138-42. [PMID: 17839368 DOI: 10.1126/science.238.4830.1138] [Citation(s) in RCA: 239] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Mussels, clams, and tube worms collected in the vicinity of hydrocarbon seeps on the Louisiana slope contain mostly "dead" carbon, indicating that dietary carbon is largely derived from seeping oil and gas. Enzyme assays, elemental sulfur analysis, and carbon dioxide fixation studies demonstrate that vestimentiferan tube worms and three clam species contain intracellular, autotrophic sulfur bacterial symbionts. Carbon isotopic ratios of 246 individual animal tissues were used to differentiate heterotrophic (8(13)C = -14 to -20 per mil), sulfur-based (8(13)C = -30 to -42 per mil), and methane-based (8(13)C = <-40 per mil) energy sources. Mussels with symbiotic methanotrophic bacteria reflect the carbon isotopic composition of the methane source. Isotopically light nitrogen and sulfur confirm the chemoautotrophic nature of the seep animals. Sulfur-based chemosynthetic animals contain isotopically light sulfur, whereas methane-based symbiotic mussels more closely reflect the heavier oceanic sulfate pool. The nitrogen requirement of some seep animals may be supported by nitrogen-fixing bacteria. Some grazing neogastropods have isotopic values characteristic of chemosynthetic animals, suggesting the transfer of carbon into the background deep-sea fauna.
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Cary SC, Fisher CR, Felbeck H. Mussel growth supported by methane as sole carbon and energy source. Science 2010; 240:78-80. [PMID: 17748823 DOI: 10.1126/science.240.4848.78] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Symbioses between chemoautotrophic bacteria and several specialized marine invertebrates are well documented. However, none of these symbioses have been demonstrated to provide sufficient energy and carbon to the host to enable it to grow. Growth rates of seep mussels collected from hydrocarbon seeps off the coast of Louisiana were measured in a controlled environment where methane was the sole carbon and energy source. The growth rates increased to a maximum of 17.2 micrometers per day in response to methane and approached zero in the absence of methane. These mussels contain methanotrophic symbiotic bacteria in their gills, which suggests that these bacteria provide their hosts with a net carbon flux originating from methane.
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Abstract
Methanotrophs, cells that consume methane (CH(4)) as their sole source of carbon and energy, play key roles in the global carbon cycle, including controlling anthropogenic and natural emissions of CH(4), the second-most important greenhouse gas after carbon dioxide. These cells have also been widely used for bioremediation of chlorinated solvents, and help sustain diverse microbial communities as well as higher organisms through the conversion of CH(4) to complex organic compounds (e.g. in deep ocean and subterranean environments with substantial CH(4) fluxes). It has been well-known for over 30 years that copper (Cu) plays a key role in the physiology and activity of methanotrophs, but it is only recently that we have begun to understand how these cells collect Cu, the role Cu plays in CH(4) oxidation by the particulate CH(4) monooxygenase, the effect of Cu on the proteome, and how Cu affects the ability of methanotrophs to oxidize different substrates. Here we summarize the current state of knowledge of the phylogeny, environmental distribution, and potential applications of methanotrophs for regional and global issues, as well as the role of Cu in regulating gene expression and proteome in these cells, its effects on enzymatic and whole-cell activity, and the novel Cu uptake system used by methanotrophs.
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Affiliation(s)
- Jeremy D Semrau
- Department of Civil and Environmental Engineering, The University of Michigan, Ann Arbor, MI, USA.
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Le Bris N, Duperron S. Chemosynthetic communities and biogeochemical energy pathways along the Mid-Atlantic Ridge: The case of Bathymodiolus azoricus. GEOPHYSICAL MONOGRAPH SERIES 2010. [DOI: 10.1029/2008gm000712] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Petersen JM, Dubilier N. Methanotrophic symbioses in marine invertebrates. ENVIRONMENTAL MICROBIOLOGY REPORTS 2009; 1:319-335. [PMID: 23765884 DOI: 10.1111/j.1758-2229.2009.00081.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Symbioses between marine animals and aerobic methane-oxidizing bacteria are found at hydrothermal vents and cold seeps in the deep sea where reduced, methane-rich fluids mix with the surrounding oxidized seawater. These habitats are 'oases' in the otherwise nutrient-poor deep sea, where entire ecosystems are fueled by microbial chemosynthesis. By associating with bacteria that gain energy from the oxidation of CH4 with O2 , the animal host is indirectly able to gain nutrition from methane, an energy source that is otherwise only available to methanotrophic microorganisms. The host, in turn, provides its symbionts with continuous access to both electron acceptors and donors that are only available at a narrow oxic - anoxic interface for free-living methanotrophs. Symbiotic methane oxidizers have resisted all attempts at cultivation, so that all evidence for these symbiotic associations comes from ultrastructural, enzymatic, physiological, stable isotope and molecular biological studies of the symbiotic host tissues. In this review, we present an overview of the habitats and invertebrate hosts in which symbiotic methane oxidizers have been found, and the methods used to investigate these symbioses, focusing on the symbioses of bathymodiolin mussels that have received the most attention among methanotrophic associations.
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Affiliation(s)
- Jillian M Petersen
- Symbiosis Group, Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359, Bremen, Germany
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Duperron S, Lorion J, Samadi S, Gros O, Gaill F. Symbioses between deep-sea mussels (Mytilidae: Bathymodiolinae) and chemosynthetic bacteria: diversity, function and evolution. C R Biol 2009; 332:298-310. [DOI: 10.1016/j.crvi.2008.08.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Accepted: 08/05/2008] [Indexed: 11/16/2022]
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Cordes EE, Bergquist DC, Fisher CR. Macro-ecology of Gulf of Mexico cold seeps. ANNUAL REVIEW OF MARINE SCIENCE 2009; 1:143-168. [PMID: 21141033 DOI: 10.1146/annurev.marine.010908.163912] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Shortly after the discovery of chemosynthetic ecosystems at deep-sea hydrothermal vents, similar ecosystems were found at cold seeps in the Gulf of Mexico. Over the past two decades, these sites have become model systems for understanding the physiology of the symbiont-containing megafauna and the ecology of seep communities worldwide. Symbiont-containing bi-valves and siboglinid polychaetes dominate the communities, including five bathymodiolin mussel species and six vestimentiferan (siboglinid polychaete) species in the Gulf of Mexico. The mussels include the first described examples of methanotrophic symbiosis and dual methanotrophic/thiotrophic symbiosis. Studies with the vestimentiferans have demonstrated their potential for extreme longevity and their ability to use posterior structures for subsurface exchange of dissolved metabolites. Ecological investigations have demonstrated that the vestimentiferans function as ecosystem engineers and identified a community succession sequence from a specialized high-biomass endemic community to a low-biomass community of background fauna over the life of a hydrocarbon seep site.
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Affiliation(s)
- Erik E Cordes
- Biology Department, Temple University, Philadelphia, Pennsylvania 19122, USA.
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Trotsenko YA, Murrell JC. Metabolic aspects of aerobic obligate methanotrophy. ADVANCES IN APPLIED MICROBIOLOGY 2008; 63:183-229. [PMID: 18395128 DOI: 10.1016/s0065-2164(07)00005-6] [Citation(s) in RCA: 248] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Yuri A Trotsenko
- G.K.Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Pushchino, Moscow 142290, Russia
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Duperron S, Halary S, Lorion J, Sibuet M, Gaill F. Unexpected co-occurrence of six bacterial symbionts in the gills of the cold seep mussel Idas sp. (Bivalvia: Mytilidae). Environ Microbiol 2008; 10:433-45. [DOI: 10.1111/j.1462-2920.2007.01465.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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3D FISH for the quantification of methane- and sulphur-oxidizing endosymbionts in bacteriocytes of the hydrothermal vent mussel Bathymodiolus azoricus. ISME JOURNAL 2008; 2:284-92. [DOI: 10.1038/ismej.2008.3] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Duperron S, Laurent MCZ, Gaill F, Gros O. Sulphur-oxidizing extracellular bacteria in the gills of Mytilidae associated with wood falls. FEMS Microbiol Ecol 2008; 63:338-49. [PMID: 18218025 DOI: 10.1111/j.1574-6941.2008.00438.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Six morphotypes of small mussels (Bivalvia: Mytilidae) were found attached to naturally sunken wood collected in the Bohol Sea (Philippines). These specimens are related to the large Bathymodiolus mussels that are found worldwide at cold seeps and hydrothermal vents. In these habitats, the mytilids harbour sulphur- and methane-oxidizing endosymbionts in their gills and depend on the energy and carbon provided by the symbionts. In this study, bacteria associated with the gills of wood-associated mussels are characterized using molecular and microscopic techniques. The existence of bacteria in the lateral zone of gill filaments in all specimens is demonstrated. Comparative analyses of 16S rRNA gene and adenosine 5'-phosphosulphate (APS) reductase gene sequences indicate that the bacteria are closely related to sulphur-oxidizing endosymbionts of Bathymodiolus. FISHs using specific probes confirm that sulphur oxidizers are by far the most abundant, if not the only bacteria present. Electron micrographs displayed mostly extracellular bacteria located between microvilli at the apical surface of host gill epithelial cells all along the lateral zone of each gill filament. In some specimens, occasional occurrence of intracellular bacteria with similar morphology was noted. This study provides the first molecular evidence for the presence of possible thiotrophic symbiosis in sunken wood ecosystems. With their epibiotic bacteria, wood-associated mussels display a less integrated type of interaction than described in their seep, vent and whale fall relatives.
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Affiliation(s)
- Sébastien Duperron
- UMR 7138 Systématique-Adaptation-Evolution, Equipe adaptation aux milieux extrêmes, Université Pierre et Marie Curie, Paris, France.
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Gros O, Guibert J, Gaill F. Gill-symbiosis in mytilidae associated with wood fall environments. ZOOMORPHOLOGY 2007. [DOI: 10.1007/s00435-007-0035-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Duperron S, Sibuet M, MacGregor BJ, Kuypers MMM, Fisher CR, Dubilier N. Diversity, relative abundance and metabolic potential of bacterial endosymbionts in three Bathymodiolus mussel species from cold seeps in the Gulf of Mexico. Environ Microbiol 2007; 9:1423-38. [PMID: 17504480 DOI: 10.1111/j.1462-2920.2007.01259.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cold seeps in the Gulf of Mexico are often dominated by mussels of the genus Bathymodiolus that harbour symbiotic bacteria in their gills. In this study, we analysed symbiont diversity, abundance and metabolic potential in three mussel species from the northern Gulf of Mexico: Bathymodiolus heckerae from the West Florida Escarpment, Bathymodiolus brooksi from Atwater Valley and Alaminos Canyon, and 'Bathymodiolus' childressi, which co-occurs with B. brooksi in Alaminos Canyon. Comparative 16S rRNA sequence analysis confirmed a single methanotroph-related symbiont in 'B.' childressi and a dual symbiosis with a methanotroph- and thiotroph-related symbiont in B. brooksi. A previously unknown diversity of four co-occurring symbionts was discovered in B. heckerae: a methanotroph, two phylogenetically distinct thiotrophs and a methylotroph-related phylotype not previously described from any marine invertebrate symbiosis. A gene characteristic of methane-oxidzing bacteria, pmoA, was identified in all three mussel species confirming the methanotrophic potential of their symbionts. Stable isotope analyses of lipids and whole tissue also confirmed the importance of methanotrophy in the carbon nutrition of all of the mussels. Analyses of absolute and relative symbiont abundance in B. heckerae and B. brooksi using fluorescence in situ hybridization (FISH) and rRNA slot blot hybridization indicated a clear dominance of methanotrophic over thiotrophic symbionts in their gill tissues. A site-dependent variability in total symbiont abundance was observed in B. brooksi, with specimens from Alaminos Canyon harbouring much lower densities than those from Atwater Valley. This shows that symbiont abundance is not species-specific but can vary considerably between populations.
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Stolyar S, Van Dien S, Hillesland KL, Pinel N, Lie TJ, Leigh JA, Stahl DA. Metabolic modeling of a mutualistic microbial community. Mol Syst Biol 2007; 3:92. [PMID: 17353934 PMCID: PMC1847946 DOI: 10.1038/msb4100131] [Citation(s) in RCA: 332] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 12/21/2006] [Indexed: 11/24/2022] Open
Abstract
The rate of production of methane in many environments depends upon mutualistic interactions between sulfate-reducing bacteria and methanogens. To enhance our understanding of these relationships, we took advantage of the fully sequenced genomes of Desulfovibrio vulgaris and Methanococcus maripaludis to produce and analyze the first multispecies stoichiometric metabolic model. Model results were compared to data on growth of the co-culture on lactate in the absence of sulfate. The model accurately predicted several ecologically relevant characteristics, including the flux of metabolites and the ratio of D. vulgaris to M. maripaludis cells during growth. In addition, the model and our data suggested that it was possible to eliminate formate as an interspecies electron shuttle, but hydrogen transfer was essential for syntrophic growth. Our work demonstrated that reconstructed metabolic networks and stoichiometric models can serve not only to predict metabolic fluxes and growth phenotypes of single organisms, but also to capture growth parameters and community composition of simple bacterial communities.
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Affiliation(s)
- Sergey Stolyar
- Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, USA
- Civil and Environmental Engineering, University of Washington, 478 Benjamin Hall Interdisciplinary Research Building, Box 355014, Seattle, WA 98195, USA. Tel.: +1 206 543 2094; Fax: +1 206 685 3836;
| | - Steve Van Dien
- Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, USA
| | | | - Nicolas Pinel
- Department of Microbiology, University of Washington, Seattle WA, USA
| | - Thomas J Lie
- Department of Microbiology, University of Washington, Seattle WA, USA
| | - John A Leigh
- Department of Microbiology, University of Washington, Seattle WA, USA
| | - David A Stahl
- Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, USA
- Civil and Environmental Engineering, University of Washington, 302 More Hall, Seattle, WA, USA. Tel.: +1 206 685 3464; Fax: +1 206 685 3836;
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Elsaied HE, Kaneko R, Naganuma T. Molecular characterization of a deep-sea methanotrophic mussel symbiont that carries a RuBisCO gene. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2006; 8:511-20. [PMID: 16761196 DOI: 10.1007/s10126-005-6135-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Accepted: 03/15/2006] [Indexed: 05/10/2023]
Abstract
In our previous investigation on the genes of 1,5-ribulose bisphosphate carboxylase/oxygenase (RuBisCO; EC 4.1.1.39) in deep-sea chemoautotrophic and methanotrophic endosymbioses, the gene encoding the large subunit of RuBisCO form I (cbbL) had been detected in the gill of a mussel belonging to the genus Bathymodiolus from a western Pacific back-arc hydrothermal vent. This study further examined the symbiont source of the RuBisCO cbbL gene along with the genes of 16S ribosomal RNA (16S rDNA) and particulate methane monooxygenase (EC 1.14.13.25; pmoA) and probed for the presence of the ATP sulfurylase gene (EC 2.7.7.4; sopT). The 16S rDNA sequence analysis indicated that the mussel harbors a monospecific methanotrophic Gammaproteobacterium. This was confirmed by amplification and sequencing of the methanotrophic pmoA, while thiotrophic sopT was not amplified from the same symbiotic genome DNA. Fluorescence in situ hybridization demonstrated simultaneous occurrence of the symbiont-specific 16S rDNA, cbbL and pmoA, but not sopT, in the mussel gill. This is the first molecular and visual evidence for a methanotrophic bacterial endosymbiont that bears the RuBisCO cbbL gene relevant to autotrophic CO(2) fixation.
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Affiliation(s)
- Hosam Easa Elsaied
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, Japan
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Duperron S, Bergin C, Zielinski F, Blazejak A, Pernthaler A, McKiness ZP, DeChaine E, Cavanaugh CM, Dubilier N. A dual symbiosis shared by two mussel species, Bathymodiolus azoricus and Bathymodiolus puteoserpentis (Bivalvia: Mytilidae), from hydrothermal vents along the northern Mid-Atlantic Ridge. Environ Microbiol 2006; 8:1441-7. [PMID: 16872406 DOI: 10.1111/j.1462-2920.2006.01038.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Bathymodiolus azoricus and Bathymodiolus puteoserpentis are symbiont-bearing mussels that dominate hydrothermal vent sites along the northern Mid-Atlantic Ridge (MAR). Both species live in symbiosis with two physiologically and phylogenetically distinct Gammaproteobacteria: a sulfur-oxidizing chemoautotroph and a methane-oxidizer. A detailed analysis of mussels collected from four MAR vent sites (Menez Gwen, Lucky Strike, Rainbow, and Logatchev) using comparative 16S rRNA sequence analysis and fluorescence in situ hybridization (FISH) showed that the two mussel species share highly similar to identical symbiont phylotypes. FISH observations of symbiont distribution and relative abundances showed no obvious differences between the two host species. In contrast, distinct differences in relative symbiont abundances were observed between mussels from different sites, indicating that vent chemistry may influence the relative abundance of thiotrophs and methanotrophs in these dual symbioses.
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Affiliation(s)
- Sébastien Duperron
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany
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DeChaine EG, Cavanaugh CM. Symbioses of methanotrophs and deep-sea mussels (Mytilidae: Bathymodiolinae). PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2006; 41:227-49. [PMID: 16623396 DOI: 10.1007/3-540-28221-1_11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The symbioses between invertebrates and chemosynthetic bacteria allow both host and symbiont to colonize and thrive in otherwise inhospitable deep-sea habitats. Given the global distribution of the bathymodioline symbioses, this association is an excellent model for evaluating co-speciation and evolution of symbioses. Thus far, the methanotroph and chemoautotroph endosymbionts of mussels are tightly clustered within two independent clades of gamma Proteobacteria, respectively. Further physiological and genomic studies will elucidate the ecological and evolutionary roles that these bacterial clades play in the symbiosis and chemosynthetic community. Due to the overall abundance of the methanotrophic symbioses at hydrothermal vents and hydrocarbon seeps, they likely play a significant, but as of yet unquantified, role in the biogeochemical cycling of methane. With this in mind, the search for methanotrophic symbioses should not be restricted to these known deep-sea habitats, but rather should be expanded to include methane-rich coastal marine and freshwater environments inhabited by methanotrophs and bivalves. Our current understanding of the bathymodioline symbioses provides a strong foundation for future explorations into the origin, ecology, and evolution of methanotroph symbioses, which are now becoming possible through a combination of classical and advanced molecular techniques.
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Affiliation(s)
- Eric G DeChaine
- Department of Organismic and Evolutionary Biology, Havard University, The Biological Laboratories, 16 Divinity Avenue, Cambridge, MA 02138, USA
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Duperron S, Nadalig T, Caprais JC, Sibuet M, Fiala-Médioni A, Amann R, Dubilier N. Dual symbiosis in a Bathymodiolus sp. mussel from a methane seep on the Gabon continental margin (Southeast Atlantic): 16S rRNA phylogeny and distribution of the symbionts in gills. Appl Environ Microbiol 2005; 71:1694-700. [PMID: 15811991 PMCID: PMC1082522 DOI: 10.1128/aem.71.4.1694-1700.2005] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Deep-sea mussels of the genus Bathymodiolus (Bivalvia: Mytilidae) harbor symbiotic bacteria in their gills and are among the dominant invertebrate species at cold seeps and hydrothermal vents. An undescribed Bathymodiolus species was collected at a depth of 3,150 m in a newly discovered cold seep area on the southeast Atlantic margin, close to the Zaire channel. Transmission electron microscopy, comparative 16S rRNA analysis, and fluorescence in situ hybridization indicated that this Bathymodiolus sp. lives in a dual symbiosis with sulfide- and methane-oxidizing bacteria. A distinct distribution pattern of the symbiotic bacteria in the gill epithelium was observed, with the thiotrophic symbiont dominating the apical region and the methanotrophic symbiont more abundant in the basal region of the bacteriocytes. No variations in this distribution pattern or in the relative abundances of the two symbionts were observed in mussels collected from three different mussel beds with methane concentrations ranging from 0.7 to 33.7 microM. The 16S rRNA sequence of the methanotrophic symbiont is most closely related to those of known methanotrophic symbionts from other bathymodiolid mussels. Surprisingly, the thiotrophic Bathymodiolus sp. 16S rRNA sequence does not fall into the monophyletic group of sequences from thiotrophic symbionts of all other Bathymodiolus hosts. While these mussel species all come from vents, this study describes the first thiotrophic sequence from a seep mussel and shows that it is most closely related (99% sequence identity) to an environmental clone sequence obtained from a hydrothermal plume near Japan.
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Affiliation(s)
- Sébastien Duperron
- IFREMER Départment Environnement Profond, Centre de Brest, Plouzané, Germany
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Dalton H. The Leeuwenhoek Lecture 2000 the natural and unnatural history of methane-oxidizing bacteria. Philos Trans R Soc Lond B Biol Sci 2005; 360:1207-22. [PMID: 16147517 PMCID: PMC1569495 DOI: 10.1098/rstb.2005.1657] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2000] [Accepted: 12/17/2004] [Indexed: 11/12/2022] Open
Abstract
Methane gas is produced from many natural and anthropogenic sources. As such, methane gas plays a significant role in the Earth's climate, being 25 times more effective as a greenhouse gas than carbon dioxide. As with nearly all other naturally produced organic molecules on Earth, there are also micro-organisms capable of using methane as their sole source of carbon and energy. The microbes responsible (methanotrophs) are ubiquitous and, for the most part, aerobic. Although anaerobic methanotrophs are believed to exist, so far, none have been isolated in pure culture. Methanotrophs have been known to exist for over 100 years; however, it is only in the last 30 years that we have begun to understand their physiology and biochemistry. Their unique ability to use methane for growth is attributed to the presence of a multicomponent enzyme system-methane monooxygenase (MMO)-which has two distinct forms: soluble (sMMO) and membrane-associated (pMMO); however, both convert methane into the readily assimilable product, methanol. Our understanding of how bacteria are capable of effecting one of the most difficult reactions in chemistry-namely, the controlled oxidation of methane to methanol-has been made possible by the isolation, in pure form, of the enzyme components.The mechanism by which methane is activated by sMMO involves abstraction of a hydrogen atom from methane by a high-valence iron species (FeIV or possibly FeV) in the hydroxylase component of the MMO complex to form a methyl radical. The radical combines with a captive oxygen atom from dioxygen to form the reaction product, methanol, which is further metabolized by the cell to produce multicarbon intermediates. Regulation of the sMMO system relies on the remarkable properties of an effector protein, protein B. This protein is capable of facilitating component interactions in the presence of substrate, modifying the redox potential of the diiron species at the active site. These interactions permit access of substrates to the hydroxylase, coupling electron transfer by the reductase with substrate oxidation and affecting the rate and regioselectivity of the overall reaction. The membrane-associated form is less well researched than the soluble enzyme, but is known to contain copper at the active site and probably iron. From an applied perspective, methanotrophs have enjoyed variable successes. Whole cells have been used as a source of single-cell protein (SCP) since the 1970s, and although most plants have been mothballed, there is still one currently in production. Our earlier observations that sMMO was capable of inserting an oxygen atom from dioxygen into a wide variety of hydrocarbon (and some non-hydrocarbon) substrates has been exploited to either produce value added products (e.g. epoxypropane from propene), or in the bioremediation of pollutants such as chlorinated hydrocarbons. Because we have shown that it is now possible to drive the reaction using electricity instead of expensive chemicals, there is promise that the system could be exploited as a sensor for any of the substrates of the enzyme.
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Affiliation(s)
- Howard Dalton
- Department of Biological Sciences, University of Warwick, Coventry, UK.
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