Investigations of potential microbial methanogenic and carbon monoxide utilization pathways in ultra-basic reducing springs associated with present-day continental serpentinization: the Tablelands, NL, CAN

Abstract

Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface environment with H2 and CH4 present. Very little, however, is known about the carbon substrate utilization, energy sources, and metabolic pathways of the microorganisms that live in this ultra-basic environment. The potential for microbial methanogenesis with bicarbonate, formate, acetate, and propionate precursors and carbon monoxide (CO) utilization pathways were tested in laboratory experiments by adding substrates to water and sediment from the Tablelands, NL, CAD, a site of present-day continental serpentinization. Microbial methanogenesis was not observed after bicarbonate, formate, acetate, or propionate addition. CO was consumed in the live experiments but not in the killed controls and the residual CO in the live experiments became enriched in 13C. The average isotopic enrichment factor resulting from this microbial utilization of CO was estimated to be 11.2 ± 0.2‰. Phospholipid fatty acid concentrations and δ13C values suggest limited incorporation of carbon from CO into microbial lipids. This indicates that in our experiments, CO was used primarily as an energy source, but not for biomass growth. Environmental DNA sequencing of spring fluids collected at the same time as the addition experiments yielded a large proportion of Hydrogenophaga-related sequences, which is consistent with previous metagenomic data indicating the potential for these taxa to utilize CO.

Continental smokers couple mantle degassing and distinctive microbiology within continents

“…The results reported here contribute to the growing body of literature that suggests lowtemperature continental springs and lakes sustained by deeply sourced fluids harbor distinctive microbial ecosystems (e.g Antony et al 2013;Suzuki et al 2013;Crespo-Medina et al 2014;Morrill et al 2014;Meyer-Dombard et al 2015). These low-temperature systems hold promise for understanding novel biodiversity and the geobiological processes that are influenced by deep subsurface geologic processes.…”

Carbon Assimilation Strategies in Ultrabasic Groundwater: Clues from the Integrated Study of a Serpentinization-Influenced Aquifer

“…5), this step could likely be bypassed as well in wells where the CO concentration is sufficiently high (Table S3). Evidence for carbon monoxide uptake (28) and the reductive acetyl-CoA pathway (27) as important carbon assimilation pathways was previously found in the Tablelands, Canada, and The Cedars, CA, respectively. In the Samail Ophiolite, it appears that carbon limitation outweighs energy limitation for the autotrophic members of microbial communities at high pH (29), making carbon compounds important as both a feedstock for biosynthesis and a source of electrons.…”

“…Biological methanogenesis appears to be occurring in other continental serpentinizing sites, such as the Voltri Massif (26) and The Cedars (19). In the Tablelands, however, no evidence of biological methane production has been detected (28), and methane production genes in metagenomes recovered from the Samail Ophiolite are likewise sparse (29). Methane cycling in ophiolite-hosted microbial communities therefore seems to vary from site to site, and further work will be required to uncover the geochemical conditions that drive its production and uptake.…”

“…Fermentation of organic matter may also lead to acetate production (19). Carbon monoxide may be used as a substrate by microbial communities in the Tablelands, Canada, but it appears to be primarily used as a source of energy rather than carbon (28). The carbonate chimneys of the Lost City Hydrothermal Field are dominated by a single species of archaea that may be capable of both production and consumption of methane in tandem (21).…”

Latitudinal distribution of microbial communities in anaerobic biological stabilization ponds: effect of the mean annual temperature

“…For example, Clostridiaceae , Flavobacteriaaceae , Turicibacteraceae , Anaerolinaceae , Actinomycetales and Synergistales (Fernandez et al ., ; Overmann, ; Jumas‐Bilak et al ., ; Ito et al ., ; Wang et al ., ), which were well known for their roles in the fermentation of macromolecular organic matter (lipid, cellulose, propionate, glucose, fatty acid and amino acid) into acetate, showed a higher abundance in the bacterial community of the sediment samples from LM area than HM area. Comamonadaceae and Pseudomonadaceae , which were known to be homo‐acetogens and could provide acetate for acetoclastic methanogens by consuming H 2 and CO 2 (Morrill et al ., ), were enriched in the sediment samples from LM area. In contrast, in the sediment samples from HM area, more than 31.9% of bacteria mainly belonged to the phylum of Bacteroidetes (Qiu et al ., ) and Proteobacteria such as Syntrophaceae (Briones et al ., ) and Syntrophorhabdaceae (Gray et al ., ), and are known to have a syntrophic relationship with hydrogenotrophic methanogens.…”