Fig. 5. Depth profiles of cell abundance, taxonomic composition of microbial communities, potential activities, and in situ energy yields in sediments of KMV#5.
(A) Cell abundance in the mud volcano samples (black dots) and the Kumano Basin sediment at Site C0002 (white dots), approximately 30 km south of KMV#5. The dashed line indicates the minimum quantification limit of sedimentary microbial cells, representing the upper limit of 95% confidence intervals of negative controls. (B and C) Taxonomic compositions of bacterial (B) and archaeal (C) communities in mud volcano sediments based on 16S ribosomal RNA (rRNA) gene sequences. Number in parentheses indicates the sample depth. nd, not detected. (D) Potential activities of homoacetogenesis, hydrogenotrophic methanogenesis, acetoclastic methanogenesis, and hydrogenase assessed by radiotracer incubation experiments. (E) Gibbs free energy yields of homoacetogenesis and hydrogenotrophic methanogenesis under in situ conditions (H2, 28.1 mM) and headspace H2 concentrations.