Haloanaerobacter salinarius sp. nov., a novel halophilic fermentative bacterium that reduces glycine-betaine to trimethylamine with hydrogen or serine as electron donors; emendation of the genus Haloanaerobacter

118

The diversity of microorganisms active within sedimentary rocks provides important controls on the geochemistry of many subsurface environments. In particular, biodegradation of organic matter in sedimentary rocks contributes to the biogeochemical cycling of carbon and other elements and strongly impacts the recovery and quality of fossil fuel resources. In this study, archaeal diversity was investigated along a salinity gradient spanning 8 to 3,490 mM Cl ؊ in a subsurface shale rich in CH 4 derived from biodegradation of sedimentary hydrocarbons. Shale pore waters collected from wells in the main CH 4 -producing zone lacked electron acceptors such as O 2 , NO 3 ؊ , Fe 3؉ , or SO 4 2؊ . Acetate was detected only in high-salinity waters, suggesting that acetoclastic methanogenesis is inhibited at Cl ؊ concentrations above ϳ1,000 mM. Most-probable-number series revealed differences in methanogen substrate utilization (acetate, trimethylamine, or H 2 /CO 2 ) associated with chlorinity. The greatest methane production in enrichment cultures was observed for incubations with salinity at or close to the native pore water salinity of the inoculum. Restriction fragment length polymorphism analyses of archaeal 16S rRNA genes from seven wells indicated that there were links between archaeal communities and pore water salinity. Archaeal clone libraries constructed from sequences from 16S rRNA genes isolated from two wells revealed phylotypes similar to a halophilic methylotrophic Methanohalophilus species and a hydrogenotrophic Methanoplanus species at high salinity and a single phylotype closely related to Methanocorpusculum bavaricum at low salinity. These results show that several distinct communities of methanogens persist in this subsurface, CH 4 -producing environment and that each community is adapted to particular conditions of salinity and preferential substrate use and each community induces distinct geochemical signatures in shale formation waters.

Section: Discussionmentioning

confidence: 99%

Salinity Constraints on Subsurface Archaeal Diversity and Methanogenesis in Sedimentary Rock Rich in Organic Matter

Waldron

Petsch

Martini

et al. 2007

118

“…Firmicutes of the Halanaerobiales are abundant in hypersaline environments, including the Great Salt Lake, the Dead Sea, oil wells, saltern ponds in France and California, and a variety of other locations (40,47,57,58,76). Known members are obligately anaerobic, moderately halophilic organisms that gain energy by fermentation of various organic compounds.…”

Section: Vol 71 2005 Phylogeny Of An Endoevaporitic Microbial Commumentioning

confidence: 99%

Community Composition of a Hypersaline Endoevaporitic Microbial Mat

Sørensen

Canfield

Teske

et al. 2005

168

148

A hypersaline, endoevaporitic microbial community in Eilat, Israel, was studied by microscopy and by PCR amplification of genes for 16S rRNA from different layers. In terms of biomass, the oxygenic layers of the community were dominated by Cyanobacteria of the Halothece, Spirulina, and Phormidium types, but cell counts (based on 4,6-diamidino-2-phenylindole staining) and molecular surveys (clone libraries of PCR-amplified genes for 16S rRNA) showed that oxygenic phototrophs were outnumbered by the other constituents of the community, including chemotrophs and anoxygenic phototrophs. Bacterial clone libraries were dominated by phylotypes affiliated with the Bacteroidetes group and both photo-and chemotrophic groups of ␣-proteobacteria. Green filaments related to the Chloroflexi were less abundant than reported from hypersaline microbial mats growing at lower salinities and were only detected in the deepest part of the anoxygenic phototrophic zone. Also detected were nonphototrophic ␥-and ␦-proteobacteria, Planctomycetes, the TM6 group, Firmicutes, and Spirochetes. Several of the phylotypes showed a distinct vertical distribution in the crust, suggesting specific adaptations to the presence or absence of oxygen and light. Archaea were less abundant than Bacteria, their diversity was lower, and the community was less stratified. Detected archaeal groups included organisms affiliated with the Methanosarcinales, the Halobacteriales, and uncultured groups of Euryarchaeota.

“…However, the transient formation of similar amounts of trimethylamine (TMA) and acetate indicates that the reduction of betaine, as found in members of the genera Clostridium and Halanaerobacter (9,10), is the first step in degradation. While acetate is utilized mainly by sulfate reducers, trimethylamine is a well-known noncompetitive substrate for methanogens (8,11), allowing them to thrive within the sulfate reduction zone.…”

mentioning

confidence: 99%

Glycine Betaine as a Direct Substrate for Methanogens (Methanococcoides spp.)

Watkins

Roussel

Parkes

et al. 2014

Nine marine methanogenic Methanococcoides strains, including the type strains of Methanococcoides methylutens, M. burtonii, and M. alaskense, were tested for the utilization of N-methylated glycines. Three strains (NM1, PM2, and MKM1) used glycine betaine (N,N,N-trimethylglycine) as a substrate for methanogenesis, partially demethylating it to N,N-dimethylglycine, whereas none of the strains used N,N-dimethylglycine or sarcosine (N-methylglycine). Growth rates and growth yields per mole of substrate with glycine betaine (3.96 g [dry weight] per mol) were similar to those with trimethylamine (4.11 g [dry weight] per mol). However, as glycine betaine is only partially demethylated, the yield per methyl group was significantly higher than with trimethylamine. If glycine betaine and trimethylamine are provided together, trimethylamine is demethylated to dimethyl-and methylamine with limited glycine betaine utilization. After trimethylamine is depleted, dimethylamine and glycine betaine are consumed rapidly, before methylamine. Glycine betaine extends the range of substrates that can be directly utilized by some methanogens, allowing them to gain energy from the substrate without the need for syntrophic partners.