CHARACTERIZATION OF NEW PHOTOTROPHIC HELIOBACTERIA AND THEIR HABITATS

Specific enrichment culture methods were used to isolate new phototrop hic heliobacteria (anoxygenic phototrophic bacteria containing bacteri ochlorophyll g) from various natural samples. A survey of terrestrial and aquatic habitats yielded heliobacteria only from soils, in particu lar rice soils, and from certain hot springs. Thirteen nonthermophilic and 7 thermophilic (capable of growth above 50 degrees C) strains of heliobacteria were isolated from such habitats and characterized as to their basic cellular and nutritional properties. Phylogenetic studies of four strains showed them to be related to known species of helioba cteria. It is concluded that, unlike phototrophic purple and green bac teria, heliobacteria are primarily (if not exclusively) terrestrial, e xcept for hot spring species. This suggests that the ecology of heliob acteria is fundamentally different from that of other anoxyphototrophs .