Abstract
Two large-celled bacterial species, Macromonas sp. and Chromatium sp., densely populate an upper boundary of the H2S layer of Lake Kaiike (bacterial plate). Growth of Macromonas sp. was examined from the laboratory incubations of the bacterial plate samples under different conditions. Enrichment of the bacterium was achieved in a medium of DUBININA and GRABOVICH (1984) which contained CH3COONa, casamino acids and yeast extract. H2S was inhibitory for the bacterial growth. Without addition of such organic matter into the bacterial plate sample, the bacterium could grow as long as Chromatium sp. existed in considerable quantity, and growth of Chromatium sp. was H2S-limited.
