Growth and flocculation of a marine photosynthetic bacterium Rhodovulum sp.

A. marine photosynthetic bacterium (PS88), identified as Rhondovulum sp., w ith flocculating ability was isolated from the sea sediment mud of a shrimp cultivation farm in Thailand. This bacterium flocculated in glutamate/mala te medium during aerobic dark or anaerobic light cultivation. The flocculat ing ability was enhanced with the increase of NaCl concentration to 6% (w/v ). When PS88 was grown in glutamate/malate medium containing 3.5% NaCl, pro tein, RNA and DNA were produced exocellularly and there was flocculation. T he yields of DNA, RNA and protein were 8.3, 62.5 and 48.5 mg/g dry cell, re spectively. The flocculated cells were deflocculated by treatment with a nu cleolytic enzyme such as RNase or DNase, while amylase, protease, trypsin, cellulase and pectinase had no deflocculating effect. These results suggest that the exocellular nucleic acids are active in flocculation.