Abstract
There is a discussion of bacterial (Chlorobium and Chloropseudomonas) ecology, morphology and growth habits emphasizing the regulation of photo-pigments (chlorophylls and carotenoids) and membrane formation in response to the growth conditions. The photometabolism of reduced S compounds, photoxidation of thiosulfate, photoproduction of H2 photometabolism of H2 CO2 fixation and photometabolism of organic compounds are emphasized.