Multiple-variant design for the enrichment of photosynthetic bacterial populations

A design for the simultaneous variation of acetate, sulfide, and sulfate concentrations in 11 related media is described. Selectivity of these media by a direct enumeration technique in solid culture was compared with that for enrichment in liquid culture. Variation of nutritional parameters resulted in the selection of Rhodospirillaceae at initial enrichment concentrations of 0.1 g or less of Na2S-9 H2O per litre and Chromatiaceae at 0.1 to 1.0 g of g of Na2S-9 H2O per litre. The survival of sulfate-reducing and coliform bacteria indicated interdependency of photosynthetic populations with the former and competition with the latter. Photosynthetic bacteria selectively cultivated in liquid enrichment were tentatively identified as Rhodopseudomonas capsulata, Rhodopseudomonas speroides. Chromatium warmingii, Chromatium okenii, Thiospirillum, and Rhabdomonas.