Genome sequencing of a type strain 41 of Carboxydocella thermautotrophica, anaerobic, thermophilic, CO-utilizing autotrophic bacterium, isolated from a terrestrial hot spring at the Geyser valley, Kamchatka Peninsula, Russia.. Carboxydocella thermautotrophica type strain 41 genome

Genus Carboxydocella forms a deeply branching family Incertae Sedis XVI in the class Clostridia and is represented by.three species capable of different modes of anaerobic metabolism, autotrophic or organotrophic. The type strain of the type species, Carboxydocella thermautotrophica, was first described as an obligate chemolithoautotroph growing exclusively by hydrogenogenic CO-oxidation. Here we describe a novel strain of C. thermautotrophica designated 019 isolated form a core sample taken at a thermal field at Uzon Caldera, Kamchatka. Metabolism of new isolate is much more versatile, together with the ability to hydrogengenic CO oxidation sharing some features with other Сarboxydocella species, e.g., the ability to organotrophic growth, acetogenesis, nitrate and Fe(III) reduction, the capacities absent in the type strain of this species. Ferric iron-containing silicate minerals glauconite and diatomite could also be used as the electron acceptors for strain 019, Fe being reduced to Fe(II) in the form of siderite. To give insights into these important metabolic features of C. thermautotrtophica, genomes of both strains of the species were sequenced using Illumina and PGM technologies. Genome analysis revealed both strains to possess gene clusters encoding an energy-converting hydrogenase and a CO-dehydrogenase (CODH), similar to those previously described in thermophilic hydrogenogenic carboxydothrophs. Six different CODH-encoding genes (maximum among known prokaryotic genomes) have been identified in each strain suggesting crucial role of CO for the metabolism of this organism. Also, a set of ca. 40 multiheme c-type cytochromes highly similar in both genomes has been identified, while only one 17-heme cytochrome gene exclusively appeared in the Fe(III)-reducing strain 019. This gene is proposed to represent a novel type of determinants of dissimilatory Fe(III) reduction in prokaryotes. Our results represent the first genome analysis of the deep phylogenetic branch Clostridia Incertae Sedis XVI family and gives insights into metabolic diversity of Carboxydocella thermautotrophica with special emphasis on its energy metabolism which might have significant ecological implications in hot terrestrial sedimentary habitats.