Isolation and Characterization of Novel Iron-Oxidizing Autotrophic and Mixotrophic Bacteria from Boiling Springs Lake, an Oligotrophic, Acidic Geothermal Habitat

Previous molecular surveys indicated Acidimicrobium sp. were abundant in samples from hot (52˚C), acidic (pH 2), oligotrophic Boiling Springs Lake (BSL) in Lassen Volcanic National Park. We isolated and characterized Acidimicrobium sp. and functionally related bacteria from BSL. The pH and temperature optima of all isolates correlate with the average summer conditions of BSL suggesting these organisms are capable of active growth in BSL. Acidimicrobium isolates were capable of oxidizing iron when grown mixotrophically or autotrophically. The isolates also oxidized iron after growth cessation, suggesting a possible role of iron oxidation in maintaining homeostasis in the absence of population growth.