Characteristics of a phototrophic bacterium isolated from the bacterial plate of Lake Kaiike.

A Phototrophic bacterium was isolated from the bacterial plate of Lake Kaiike (surface, 0.15 km2; max. depth, 11.6 m) by use of the medium of KÄMPF and PFENNIG (1980). The bacterium was coccoid or diplococcoid, 1-3 μm in length, and contained bacteriochlorophyll a. When much H2S was present, the bacterium united to large sedimentary aggregates, and all cells contained sulfur globules. With decreasing H2S concentration, the cells became motile and changed into a purple suspension. At depletion of H2S, the bacterium consumed sulfur globules, and it entered the stationary growth phase. The bacterium was similar to Thiocystis violacea. Effects of some environmental factors such as pH, light intensity, temperature, NaCl concentration and sulfur compounds on the bacterial growth were examined.