Under selective culture conditions, two pure cultures (strain G and strain SG) of the purple nonsulfur photosynthetic bacteria containing bacteriochlorophyll b were isolated from pulp effluent and sludge of sewage treatment plant by means of agar shake dilution. Although the cells of strain G and strain SG contained bacteriochlorophyll b and carotenoids, intra-cytoplasmic membranes were of lamellar type parallel to cytoplasmic membrane, the two strains differ in using various organic carbon sources, depending on reduced sulfur compounds and assimilate sulfate. According to Bergey's Manual of Systematic Bacteriology Volume 3, strain G was identified to be Rhodopseudomonas viridis,, strain SG was identified to be Rhodopseudomonas sulfoviridis.