패류(Scapharca broughtonii) 유래의 용혈활성 미생물 다양성 분석

Abstract

The southern coast of Korea is important for the ark shell (Scapharca broughtonii) aquaculture, but the productivity was rapidly reduced during the previous decade by mass mortality. To overcome this economic loss, investigations only focused on environmental factors, and microbiological researches were performed insufficiently. In this study, two sites (Gangjin and Jinhae bay) were selected for their high and low rate of mortality, respectively, and the existence of microflora from underwater sediments in the bodies of S. broughtonii was analyzed. We screened the whole body of each sample and chose unique colonies, which exhibit alpha- and beta-hemolytic activity, for identification. The microflora in S. broughtonii was less variable than sediments, and restricted species were isolated. We identified 17 genera of 88 species and 16 genera of 64 species from the two bays, respectively. A major proportion was comprised of Bacillus species, with the Bacillus cereus group being the most common species among the Bacillus strains, while Paenibacillus, Lynsilbacillus, and Vibrio species were the second most abundant species. At the genus level, there were no significant microbial differences between the two coastal regions. 64 species were isolated from rare site (Jinhae bay), but more species (88) with greater variety were isolated from the frequent site (Gangjin bay). Therefore, it was assumed that the cause of mass mortality lay in the difference in specie-level diversity, and conducting investigations on the diagnosis of pathogenic species by challenging tests using isolated unique species.