2009 Volume 118 Issue 3 Pages 564-577
There have been many studies on the microbial ecology in methane-seep sites related to mud volcanoes. This microbial ecosystem is supported by chemosynthetic microorganisms which depend on not on sunlight but on high-flux methane and sulfate.
In the subseafloor at the methane-seep sites, anoxic methane oxidation (AOM) occurs in the mixing zone of methane and sulfate. The primary microorganisms causing AOM are anaerobic methanotrophic archaea (ANME) and sulfate-reducing δ-proteobacteria (SRB). It is known that there are three groups of ANME (ANME-1, ANME-2, ANME-3) in deep-sea environments. These ANMEs are taxonomically related to known methanogens. ANME-2 and ANME-3 form symbiotic consortia with SRB, while ANME-1 does not form the symbiotic consortia. However, none of these microorganisms has been isolated yet. Therefore, details about ANMEs such as energy-metabolisms are still unknown. However, information about these microorganisms has recently been collected by the culture-independent analyses, such as metagenomic analysis. From these analyses, it has been proposed that ANME performed AOM by reverse-methanogenesis that proceeded in the opposite direction of known methanogenesis by methanogens.
Hydrogen sulfide is produced through AOM. This supports other ecosystems at the sediment surface. At the sediment surface, H2S supports H2S-oxidizing microorganisms. There are also invertebrates including mussels, clams and tubeworms which harbor chemosynthetic bacteria in their bodies to gain organic compounds.
Here, I introduce the activities of microorganisms and invertebrates living at methane-seep sites related to mud volcanoes.
