Chemosynthetic bacterial signatures in Frenulata tubeworm Oligobrachia sp. in an active mud volcano of the Canadian Beaufort Sea

Abstract

We performed bulk and compound-specific stable carbon isotope analyses to constrain specific carbon sources utilized for the chemosynthetic metabolisms of bacterial communities inhabiting the tube and worm of Oligobrachia sp. Together with bulk carbon isotopic compositions (-57.1 +/- 1.2 parts per thousand, mean +/- SD) observed in the worm, the most depleted C-13 values of predominant fatty acids (FAs) (i.e. C16:1 omega 7 [-71.4 +/- 2.9 parts per thousand] and C18:1 omega 7 [-76.7 +/- 4.3 parts per thousand]) indicated that sulfur-oxidizing symbionts were preferentially utilizing anaerobic oxidation of methane-derived dissolved inorganic carbon (-31.6 +/- 4.2 parts per thousand), rather than methane (-59.5 +/- 3.9 parts per thousand), as a carbon source. In contrast, the isotopic signatures of FAs of the tube sections indicated that both autotrophic and heterotrophic bacterial communities utilized dissolved inorganic carbon supplied from ambient bottom seawater and sediment porewater. In this regard, the metabolisms of chemosynthetic bacterial communities inhabiting the tube may be regarded as potentially supporting tubeworm nutrition. Given that the tubeworm host incorporates locally adapted microbial communities, the isotopic signatures suggest that different micro-niches identified from the tube and the worm, particularly in relation to complex metabolic interactions, may be correlated with in situ microbial processes in sediment and bottom seawater.