ANOXYGENIC PHOTOTROPHIC BACTERIA IN EUTROPHIC COASTAL LAGOONS OF THE FRENCH MEDITERRANEAN AND ATLANTIC COASTS (PREVOST LAGOON, ARCACHON BAY, CERTES FISHPONDS)

Sediment samples collected from coastal lagoons on the French Mediterr anean (Prevost Lagoon) and Atlantic coasts (Arcachon Bay and Certes fi shponds) have been studied in order to determine the population densit ies and the species diversity of the different groups of anoxygenic ph ototrophic bacteria (purple sulfur bacteria, purple nonsulfur bacteria and green sulfur bacteria) present in these ecosystems. Several strai ns of each group were isolated in pure culture and characterized by th eir physiological properties. The occurrence of purple nonsulfur bacte ria in organic rich sediments of the Arcachon Bay and the dominance of purple sulfur bacteria in the Prevost lagoon and Certes fishponds are discussed with respect to their community structure and abundance. Th e diversity differences of the phototrophic bacterial strains isolated from both environments are also discussed.