유해성 적조생물 Cochlodinium polykrikoides에 대한 Brachybacterium sp. KB-1의 살조 효과

Abstract

In this study, I have investigated the distributions and algicidal effects of marine bacteria that tend to kill the red tide microalgae, Cochlodinium polykrikoides. C. polykrikoides was the most dominant species in September and several bacteria that showed the algicidal effect on the growth of C. polykrikoides was detected from the same samples of sea water in September. Using the method of biochemical analysis, a algicidal bacterium was identified as Brachybacterium sp. KB-1. To summarize, C. polykrikoides-algicidal bacteria were detected at 10 ² to 10 ³ cells/ml of seawater samples during the survey period, and the bloom was observed in September by containing 4.8×10³ cells/ml. It appears, however, that the number of these bacteria is decreased (2.0×10 ² cells/ml) in October. A total of 100 strains were isolated from seawater samples and seawater filter(pore size, 0.8 ㎛) containing mixed culture of C. polykrikoides. in which the mixed culture was grown in f/2-Si medium. As results, I have successfully isolated Brachybacterium sp. KB-1 which shows a remarkable algicidal effects against C. polykrikoides. 1.2×10² cells/ml of C. polykrikoides were decreased to less than 3×10² cells/ml within 24 hours after inoculation of Brachybacterium sp. KB-1 into C. polykrikoides. In addition, the killing effects were increased in accordance with bacterial cell densities inoculated in a dose dependent manner. Especially, the filtate of algicidal bacterium culture ( pore size, 0.1 ㎛ ) revealed a dramatic effect in which C. polykrikoides were decreased to less than 2×10² cells/ml of culture within 3hrs, 6hrs, 30hrs after inoculation of the culture filtrate with concentration of 5%, 10%, 15%, respectively. The result indicated that the algicidal effect was mediated by a certain substance released by Brachybacterium sp. KB-1.