Isolation and characterization of phototrophic purple nonsulfur bacteria from Chloroflexus and cyanobacterial mats in hot springs

Chloroflexus and cyanobacterial mats developing at 50-65 degrees C in Nakanoyu and Nakabusa hot springs, Japan, were collected and cultivated phototrophically at 50 and 37 degrees C. Chloroflexus organisms grew when incubated at 50 degrees C, whereas the incubation at 37 degrees C resulted in the enrichment of pink- to brown-colored cultures, from which different species of phototrophic purple nonsulfur (PPNS) bacteria were isolated. The majority of the isolates grew at temperatures of up to 45 degrees C and optimally at around 40 degrees C. The high frequencies of the occurrence of PPNS bacteria in hot spring microbial mats suggest that these environments offer a favorable ecological niche for these bacteria.