STUDIES ON PHOTOAUTOTROPHIC GROWTH OF NEW ISOLATED NONSULFUR PURPLE BACTERIA AT EXPENSE OF MOLECULAR HYDROGEN

By incubating samples of mud in a mineral salt medium containing 0.1% NH4Cl and 0.01% yeast extract under an atmosphere of 90% H2 and 10% CO2 in the light, eight strains of nonsulfur purple bacteria capable of photoautotrophic growth at the expense of H2-CO2 were enriched and isolated. The bacteria were characterized by their microscopical features and their ability to use various organic compounds for growth. Three strains of Rps. capsulata need thiamine as a growth factor and two strains of R. rubrum biotin. The Rps. gelatinosa strain is dependent on thiamine and nicotinic acid. One of two Rps. palustris strains grows slowly in a medium completely free of growth factors, the other strain is dependent on the presence of 0.01% yeast extract. The growth of all strains is markedly stimulated by small amounts (0.01%) of amino acids or yeast extract. The three Rps. capsulata strains differ significantly from the other strains with regards to their fast photoautotrophic growth (doubling time: 17-23 h in a mineral salt medium with thiamine, 10.5-11 h in a medium with 0.01% yeast extract). The hydrogenase activities of all strains are strongly dependent on the culture conditions. The lowest activities are obtained after photoheterotrophic growth in a medium with NH4Cl as the nitrogen source, moderate activities after photoheterotrophic growth in a medium with glutamate as the nitrogen source and maximum activities after photoautotrophic growth at the expense of H2-CO2. Maximum rates of CO2-fixation are also obtained after photoautotrophic growth. © 1968 Springer-Verlag.