Variations in Archaeal and Bacterial Diversity Associated with the Sulfate-Methane Transition Zone in Continental Margin Sediments (Santa Barbara Basin, California)

Abstract

The sulfate-methane transition zone (SMTZ) is a widespread feature of continental margins, representing a diffusion-controlled interface where there is enhanced microbial activity. SMTZ microbial activity is commonly associated with the anaerobic oxidation of methane (AOM), which is carried out by syntrophic associations between sulfate-reducing bacteria and methane-oxidizing archaea. While our understanding of the microorganisms catalyzing AOM has advanced, the diversity and ecological role of the greater microbial assemblage associated with the SMTZ have not been well characterized. In this study, the microbial diversity above, within, and beneath the Santa Barbara Basin SMTZ was described. ANME-1-related archaeal phylotypes appear to be the primary methane oxidizers in the Santa Barbara Basin SMTZ, which was independently supported by exclusive recovery of related methyl coenzyme M reductase genes (mcrA). Sulfate-reducing Deltaproteobacteria phylotypes affiliated with the Desulfobacterales and Desulfosarcina-Desulfococcus clades were also enriched in the SMTZ, as confirmed by analysis of dissimilatory sulfite reductase (dsr) gene diversity. Statistical methods demonstrated that there was a close relationship between the microbial assemblages recovered from the two horizons associated with the geochemically defined SMTZ, which could be distinguished from microbial diversity recovered from the sulfate-replete overlying horizons and methane-rich sediment beneath the transition zone. Comparison of the Santa Barbara Basin SMTZ microbial assemblage to microbial assemblages of methane seeps and other organic matter-rich sedimentary environments suggests that bacterial groups not typically associated with AOM, such as Planctomycetes and candidate division JS1, are additionally enriched within the SMTZ and may represent a common bacterial signature of many SMTZ environments worldwide.

Ocean currents shape the microbiome of Arctic marine sediments

“…Along with sulfate reducers, methanogens and methanotrophs, the Japan Sea candidates, Obsidian pool candidates and Chloroflexi, all of which have unclear biogeochemical roles, are routinely observed in high abundance in methane-containing sediments (Orphan et al, 2001;Webster et al, 2004;Inagaki et al, 2006;Liao et al, 2009;Hamdan et al, 2011). These observations suggest that communities in methane-containing sediments in the global ocean bear similar characteristics (Harrison et al, 2009;Knittel and Boetius, 2009). The phylogenetic and biogeochemical commonalities in these habitats imply that lineages have been conserved over time, possibly due to physical isolation and stable environmental conditions.…”

“…Many studies have characterized the composition and ecological role of microorganisms in methanecontaining marine sediments around the world (Inagaki et al, 2006;Heijs et al, 2007;Parkes et al, 2007;Pernthaler et al, 2008;Wegener et al, 2008;Harrison et al, 2009;Hamdan et al, 2012). These works assist in understanding the biological controls on oceanic methane and may contribute to establishing baselines to monitor change in marine sediments.…”

Thermophilic anaerobic oxidation of methane by marine microbial consortia

“…Cells of both groups form dense consortia with specific bacterial phylotypes clustering with sulfate-reducing Deltaproteobacteria (most often within Desulfosarcinales, Seep-SRB-1a; Schreiber et al, 2010) or relatives of Desulfobulbus Lösekann et al, 2007;Pernthaler et al, 2008;Schreiber et al, 2010), respectively. A third phylogenetic group, ANME-1, is dominant in the microbial mats covering chimney structures at methane seeps in the Black Sea (Michaelis et al, 2002; in situ temperature of B10 1C), and in several diffusive methane interfaces (Thomsen et al, 2001;Lanoil et al, 2005;Harrison et al, 2009;Aquilina et al, 2010). The anaerobic oxidation of methane (AOM) habitats with these ANME types exhibit temperatures between À1.5 and 20 1C Supplementary Table 1).…”

Stratified Communities of Methanogens in the Jiulong River Estuarine Sediments, Southern China

“…However, nearly all methane is oxidized microbially in the marine sediment [4]. Till date, numerous studies on methanogen communities mainly focused on seep, gas hydrate, continental-margin, lake and tidal sediments with universal archaeal primers which were not specific to methanogen [4][5][6][7]. These results failed to detect the whole methanogen communities because they only represented a minor part of archaea in these environments.…”