ABSTRACT
Roseiflexus sp. strains were cultivated from a microbial mat of an alkaline siliceous hot spring in Yellowstone National Park. These strains are closely related to predominant filamentous anoxygenic phototrophs found in the mat, as judged by the similarity of small-subunit rRNA, lipid distributions, and genomic and metagenomic sequences. Like a Japanese isolate, R. castenholzii, the Yellowstone isolates contain bacteriochlorophyll a, but not bacteriochlorophyll c or chlorosomes, and grow photoheterotrophically or chemoheterotrophically under dark aerobic conditions. The genome of one isolate, Roseiflexus sp. strain RS1, contains genes necessary to support these metabolisms. This genome also contains genes encoding the 3-hydroxypropionate pathway for CO2 fixation and a hydrogenase, which might enable photoautotrophic metabolism, even though neither isolate could be grown photoautotrophically with H2 or H2S as a possible electron donor. The isolates exhibit temperature, pH, and sulfide preferences typical of their habitat. Lipids produced by these isolates matched much better with mat lipids than do lipids produced by R. castenholzii or Chloroflexus isolates.
Phylogenetic characterization of microbial mats and streamers from a Japanese alkaline hot spring with a thermal gradient.
