OCCURRENCE AND DISTRIBUTION OF HETEROTROPHIC BACTERIA IN SEA WATER FROM THE KAMOGAWA BAY

An investigation of the bacterial flora of the sea water from the inshore environment of the Kamogawa Bay (Fig. 1) was carried out at the four seasons of 1961. The bacterial population seemed to decrease in winter and increase in other seasons (Table 2). Some 475 strains of bacteria were isolated by membrane filter method and investigated their morphological and cultural characteristics using test media containing 3% of NaCl. For cultures isolated in winter, optimun temperatures for growth were relatively low and the greater part of them failed to grow at 37°C. (Table 5). Most of them (82% of the isolates) were sea-water-loving (halophilic) species showing the optimal growth at about 3% of NaCI concentration and no visible growth of these isolates was occurred at NaC1 concentration lower than 0.1%. Remaining one fifth of the cultures showed good growth on the media oontaining less than 0.1% of NaCl and had no marked optimum growth range for NaCl concentration. Distinct differences in the distribution of bacterial genera was observed between halophilic and non-halophilic bacteria, halophilic group was mainly consisted of Pseudomonas, Achromo-bacter, Vibrio, and Photobacterium, while dominant genera in non-halophilic group were Pseudomonas, Achromobacter, Bacillus and Flavobacterium. (Table 6). The composition of the bacterial flora analyzed according to the scheme of Fig. 3 was as follows; Vibrio 37.3%, Pseudomonas 29.8%, Achromobacter 21.3%, Aeromonas 0.4%, Photobacterium 0.4%, Flavobacterium 2.1%, Bacillus 5.5%, Micrococcus 0.4%, Coryneforms (Pseudobacterium) 0.4% and Miscellaneous 2.3% (Table 6). Among the isolated cultures, a species of Vivrio, possessing the charecteristics similar to those of the “pathogenic halophile which was isolated from the patients of a gastroenteric disease”, constituted considerable proportions through a year.