Abstract
Purple nonsulfur bacteria occurred in relatively high numbers (105 to 107 viable cells/ml) in surface waters of ditches, paddy fields, and tide pools under oxygen-limited conditions, whereas they were absent or found in small numbers in eutrophic pond and river waters in which too much oxygen was present. The phototrophic bacteria were recovered from all activated sludeg plants studied, with numbers of 102 to 105 viable cells/mgdry sludge. In general, food industrial wastewater activated sludge samples yielded higher numbers of the photorophic bacteria than did sewage activated sludge samples. These results suggest that the organic nutrient composition of the waste is an important factor controlling the occurrence of these bacteria in activated sludge. The phototrophic bacterial flora of the activated sludge and the other aquatic environments was mainly represented by facultatively aerobic species such as Rhodopseudomonas sphaeroides, Rhodopseudomonas palustris, Rhodopseudomonas gelatinosa, and Rhodopseudomonas capsulata.
