Frank T. Robb, Juan M.Gonzalez, Tatyana Sokolova, Stephen M. Techtmann, Nicolai Chernyh, Alexander Lebedinski, Luke J. Tallon, Kristie Jones, Martin Wu, Jonathan A. Eisen
Geothermal Biology and Geochemistry in YNP [TBI Text!], 2005 1:163-170
Chemolithotrophic metabolism fuels primary production in many hydrothermal ecosystems, representing energy conservation
strategies that may be independent of sunlight. Many autotrophic metabolic pathways in geothermal communities depend
on H2; however, in this paper we focus on anaerobic carboxydotrophs that are capable of using CO as a carbon and energy
source, producing H2 and CO2. We have recently completed the genome sequence of an autotrophic carboxydotroph,
Carboxydothermus hydrogenoformans, which appears to be a specialist in CO-oxidation, encoding five unlinked genetic loci
capable of expressing CO dehydrogenase. Because of their global occurrence in geothermal environments, we propose that
CO-utilizing organisms play important roles in anaerobic microbial consortia. To understand the role of CO-utilizing bacteria
in Yellowstone hot springs we isolated and described a novel H2-producing bacterium (strain Nor1) from an Fe-rich site in
Norris Geyser Basin, YNP. Strain Nor1 is a low-G+C Gram-positive bacterium belonging to the division Firmicutes, and
grows chemolithotrophically at 75°C on CO (generation time 1.5 h), producing equimolar quantities of H2 and CO2. Strain
Nor1 is also capable of chemoautotrophic growth on FeIII and Se, as well as growing heterotrophically on glucose and several
sugars, producing acetate, H2, and CO2. We have proposed that strain Nor1 be assigned to a new genus, Thermosinus gen. nov.
The type species is Thermosinus carboxydivorans sp. nov. (type strain, Nor1T =DSM 14886T; Sokolova et al. 2004). It is evident
that CO-dependent hydrogenogenic metabolism occurs in a diverse phylogenetic context and can be accompanied by a varied
repertoire of alternative trophic strategies.
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