Dataset Information

Growth and methane oxidation rates of anaerobic methanotrophic archaea in a continuous-flow bioreactor.

ABSTRACT: Anaerobic methanotrophic archaea have recently been identified in anoxic marine sediments, but have not yet been recovered in pure culture. Physiological studies on freshly collected samples containing archaea and their sulfate-reducing syntrophic partners have been conducted, but sample availability and viability can limit the scope of these experiments. To better study microbial anaerobic methane oxidation, we developed a novel continuous-flow anaerobic methane incubation system (AMIS) that simulates the majority of in situ conditions and supports the metabolism and growth of anaerobic methanotrophic archaea. We incubated sediments collected from within and outside a methane cold seep in Monterey Canyon, Calif., for 24 weeks on the AMIS system. Anaerobic methane oxidation was measured in all sediments after incubation on AMIS, and quantitative molecular techniques verified the increases in methane-oxidizing archaeal populations in both seep and nonseep sediments. Our results demonstrate that the AMIS system stimulated the maintenance and growth of anaerobic methanotrophic archaea, and possibly their syntrophic, sulfate-reducing partners. Our data demonstrate the utility of combining physiological and molecular techniques to quantify the growth and metabolic activity of anaerobic microbial consortia. Further experiments with the AMIS system should provide a better understanding of the biological mechanisms of methane oxidation in anoxic marine environments. The AMIS may also enable the enrichment, purification, and isolation of methanotrophic archaea as pure cultures or defined syntrophic consortia.

SUBMITTER: Girguis PR

PROVIDER: S-EPMC194967 | biostudies-literature | 2003 Sep

REPOSITORIES: biostudies-literature

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Growth and methane oxidation rates of anaerobic methanotrophic archaea in a continuous-flow bioreactor.

Girguis Peter R PR Orphan Victoria J VJ Hallam Steven J SJ DeLong Edward F EF

Applied and environmental microbiology 20030901 9

Anaerobic methanotrophic archaea have recently been identified in anoxic marine sediments, but have not yet been recovered in pure culture. Physiological studies on freshly collected samples containing archaea and their sulfate-reducing syntrophic partners have been conducted, but sample availability and viability can limit the scope of these experiments. To better study microbial anaerobic methane oxidation, we developed a novel continuous-flow anaerobic methane incubation system (AMIS) that si ...[more]

PMID: 12957936

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Project description:In this study, we investigated Mn3+-cycling microbial populations enriched from Lake Matano, Indonesia using metagenomics and metaproteomics. Lake Matano contains an active Mn cycle that links the oxic-anoxic interface with anoxic deep waters that are enriched in iron and manganese, and depleted in sulfate, phosphate, and oxidized nitrogen (Crowe et al., 2008; Jones et al., 2011). Sediments were incubated with sequential transfers for ~1 year with Mn3+ as the sole electron acceptor and methane as organic carbon until achieving sediment-free conditions. Here we investigate this novel species of Dechloromonas (Betaproteobacteria), “Candidatus Dechloromonas occultata,” which was the dominant population in enrichment cultures with active Mn3+ reduction. “Ca. D. occultata” expressed electron conduits related to those involved in Fe2+ oxidation (Mto-like), as well as a novel cytochrome c-rich gene cluster putatively involved in extracellular electron transfer, and an atypical nitrous oxide reductase. According to ribosomal counts, Dechloromonas outnumber Geobacter. In terms of functional genes, Dechloromonas expresses a wider variety and number of genes. Dechloromonas therefore seems to have a (selective?) advantage over Geobacter. Previous experiments revealed that Dechloromonas express nitrogen regulators, reductases and scavenging genes, as well as many carbon central metabolic pathways, and aromatic carbon degradation pathways. Dechloromonas is a beta proteobacteria, and these are "experts" in nitrogen metabolism. Geobacter, on the other hand, is well known for carbon degradation. Our previous experiments lead to our hypothesis that Dechloromonas is more active because they are more successful at acquiring nitrogen, a limiting nutrient for Geobacter. This would further suggest that carbon is not the limiting nutrient. We will test 2 hypotheses with the next suite of experiments 1) pyrophosphate supports the community, by allowing carbon fixation , 2)Dechloromonas has a (selective?) advantage over Geobacter. To test this hypothesis, bioreactors will be used to grow biotriplicate cultures of (1)- CH4 vs. pyrophosphate and (2)-CH4 vs. Mn(III) pyrophosphate. Here we have analyzed whole cell pellets using gas phase fractionations on the Q Exactive. Are Dechloromonas capable of out-competing Geobacter when grown in media with methane as the only carbon source bioreactors because they are capable of acquiring more nitrogen? Source of inoculum. Lake Matano is a metal-rich, ancient ocean analog (Crowe et al. 2011, Jones et al. 2011). Organic carbon in Lake Matano is mostly mineralized via methanogenesis before reaching the iron-rich sediments, limiting organic matter bioavailability for metal-reducers (Kuntz et al. 2015). A 15-cm sediment core from 200 m water depth in Lake Matano, Sulawesi Island, Indonesia (02°26′27.1′′S, 121°15′12.3′′E; in situ sediment temperature ~27°C) was sampled in November 2014 and sub-sampled at 5 cm increments. Sediments were sealed in gas-tight Mylar bags with no headspace (Hansen et al. 2000) and stored at 4°C until incubations began in December 2015.

Project description:The anaerobic oxidation of methane by anaerobic methanotrophic (ANME) archaea in syntrophic partnership with deltaproteobacterial sulfate-reducing bacteria (SRB) is the primary mechanism for methane removal in ocean sediments. The mechanism of their syntrophy has been the subject of much research as traditional intermediate compounds, such as hydrogen and formate, failed to decouple the partners. Recent findings have indicated the potential for extracellular electron transfer from ANME archaea to SRB, though it is unclear how extracellular electrons are integrated into the metabolism of the SRB partner. We used metagenomics to reconstruct eight genomes from the globally distributed SEEP-SRB1 clade of ANME partner bacteria to determine what genomic features are required for syntrophy. The SEEP-SRB1 genomes contain large multiheme cytochromes that were not found in previously described free-living SRB and also lack periplasmic hydrogenases that may prevent an independent lifestyle without an extracellular source of electrons from ANME archaea. Metaproteomics revealed the expression of these cytochromes at in situ methane seep sediments from three sites along the Pacific coast of the United States. Phylogenetic analysis showed that these cytochromes appear to have been horizontally transferred from metal-respiring members of the Deltaproteobacteria such as Geobacter and may allow these syntrophic SRB to accept extracellular electrons in place of other chemical/organic electron donors.IMPORTANCE Some archaea, known as anaerobic methanotrophs, are capable of converting methane into carbon dioxide when they are growing syntopically with sulfate-reducing bacteria. This partnership is the primary mechanism for methane removal in ocean sediments; however, there is still much to learn about how this syntrophy works. Previous studies have failed to identify the metabolic intermediate, such as hydrogen or formate, that is passed between partners. However, recent analysis of methanotrophic archaea has suggested that the syntrophy is formed through direct electron transfer. In this research, we analyzed the genomes of multiple partner bacteria and showed that they also contain the genes necessary to perform extracellular electron transfer, which are absent in related bacteria that do not form syntrophic partnerships with anaerobic methanotrophs. This genomic evidence shows a possible mechanism for direct electron transfer from methanotrophic archaea into the metabolism of the partner bacteria.

Dataset Information

Growth and methane oxidation rates of anaerobic methanotrophic archaea in a continuous-flow bioreactor.

Publications

Growth and methane oxidation rates of anaerobic methanotrophic archaea in a continuous-flow bioreactor.

Similar Datasets

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