HETEROTROPHIC BACTERIAL ABUNDANCE AND DIVERSITY IN THE FARMING ENVIRONMENT AND GUTS OF THE OYSTER CRASSOSTREA HONGKONGENSIS

摘要

Currently, the knowledge of ecology and function of bacteria harbored by molluscs is very limited. In this study, quantity and richness of culturable heterotrophic bacteria (CHB) in seawater of the farming environment and guts of the oyster Crassostrea hongkongensis were determined monthly, with classical, biochemical, and molecular methods. About 800 randomly selected bacterial strains were purified and identified. Quantities of CHB and vibrios, ranging from 2.3x10(3) to 2.2x10(5) CFU/ml and 1.6x10(2) to 3.0x10(3) CFU/ml, respectively, were present in the farming seawater, whereas those in the oyster C. hongkongensis ranged from 5.3x10(4) to 5.4x10(6) CFU/g and 6.0x10(3) to 1.4x10(5) CFU/g, respectively. Vibrio spp., Pseudoalteromonas spp., Bacillus spp., and Shewanella spp. appeared almost every month. Richness of heterotrophic microbial communities of the seawater and the oysters was very similar and peaked in August. Variation in the diversity (Shannon index) of CHB in the seawater and in the oysters was similar, a significant positive correlation was showed between them (r = 0.894), and their diversities were both peaked in August. Statistical analysis showed that salinity has more important impact on quantity of CHB in seawater. Similarly, temperature had more important impact on that in the oysters. Important threshold data were analyzed to further explain the relationships.