Bacteriological Studies on the Unusually High Mortality of Ostrea gigas in Hiroshima Bay-II

The authors have bacteriologically studied on the causes of high mortality of oyster, isolating some bacteria from it in Hiroshima Bay. The results were as follows. 1. Bacterial population cultured from normal oyster from April to June 1954, was higher at room temperature than at 37°C., and higher on blood agar than on agar-agar. 2. Bacterial population cultured from abnormally dead oyster was almost same degree with that previously reported. 3. The three strains isolated from dead oyster belonged to genus Achromobacter, were pathogenic against normal oyster and induced same pathological and bacteriological changes as shown in abnormally dead oyster. 4. The virulence of these strains became lower with subcultures on artificial medium.