Photoautotrophy by the purple nonsulfur bacterium Rhodopila globiformis in an acidic, moderately sulfidic warm spring

Populations of the acidophilic purple nonsulfur bacterium Rhodopila globiformis were identifiedin two geographically distinct thermal areas in Yellowstone National Park (Wyoming, USA), asconfirmed by 16S rRNA gene sequencing and detection of unique ketocarotenoids. Though originally isolated and grown in culture-dependent studies photoheterotrophically, in nature R. globiformis appears to prefer photoautotrophy, utilizing a stable supply of DIC afforded by injection of CO 2 -rich gases. To ourknowledge, these are the most acidic conditions under which photoautotrophy has been observedin the domain Bacteria.