유해성 침편모조류 Chattonella marina에 대한 Bacillus sp. C-4의 살조 효과

Abstract

본 논문은 적조대책의 일환으로 적조 원인 생물인 Chattonella marina를 살조시키는 세균을 분리하여 C. marina에 대한 살조력을 검증하였다. 울진 해수 중의 살조세균을 100여종 분리하였으며, 이 중 살조력이 가장 우수한 Bacillus sp. C-4를 선별하였다. Bacillus sp. C-4의 최적 배양조건은 30℃, 3% NaCI, pH 7.0이었다. 이 살조세균은 최적 조건에서 6시간 정도의 유도기를 거친 후 대수증식기로 접어들어, 20시간 후 정지기로 접어들었다. Bacillus sp. C-4 는 C. marina에 살조인자를 분비하였으며,Bacillus sp. C-4 의 균수에 따른 살조 효과는 초기 세균 밀도가 102 cell/㎖이 되도록 접종한 후, 약 18시간 후 C. marina의 세포수가 50% 반감하여 31×102cells/㎖로 줄어들었으며 48시간 후에는 10×102cells/㎖ 이하로 감소하였다. Bacillus sp. C-4 의 배양 여과액의 최종농도가 1%, 5%, 10%가 되도록 첨가한 경우, 18시간 후의 C. marina의 개체수는 control에 비해 10%에서는 88%가 사멸되었으며, 5%에서는 82%가, 1%에서는 74%가 사멸되었다. 그리고 살조물질은 열과 pH에 안정한 것으로 나타났다. 따라서 2차 오염이 없는 자연 생태조화형, 환경 친화적인 적조 방제 기술의 기초 자료를 제공한다.

In order to isolate the bioactive compounds exhibiting algicidal effects from the marine bacterium Chattonella marina, seawater was collected from the coastal water at Uljin from June to October 2006. A total of 100 strains were isolated from the seawater samples. Seawater was filterated with the mesh having a 0.2 μm. The mixed culture of C. marina was grown in f/2-Si medium and we successfully isolated bacteria which show a remarkable algicidal effects against C. marina. One strain of marine bacteria, showing strong algicidal activity for C. marina, was isolated by Cell Culture Insert. This microorganisms were tested by examining its morphological, biochemical properties. Also we have analyzed 16S rRNA gene sequencing for identification. Isolated strain was tentatively identified to be Bacillus sp. and designated as Bacillus sp. C-4. The optimum culture conditions of Bacillus sp. C-4 for growth and production of algicide against C. marina were initial pH 7, 3% NaCl and 200 rpm agitation at 30℃. And Bacillus sp. C-4 relatively grew in conditions which were 20 ~ 50℃, pH 5 ~ 9, NaCl 0 ~ 7%. Algicidal activity of Bacillus sp. C-4 against C. marina was 99% at lately log phase, 84% at early log phase, 60% at stationary, respectively. In cell densities, C. marina 0.7 × 10³ cells/ml was decreased to less than 0.3 × 10³ cells/mL within 18 hours after incubation of 102 Bacillus sp. C-4. C. marina were reduced by half within 6 hours after incubation of 10³ Bacillus sp. C-4. In addition, the killing effects were increased in accordance with bacterial cell densities. Especially, the filtrate of algicidal bacterium culture (pore size, 0.1 μm) revealed a dramatic effect in which C. marina were decreased to less than 50 cells/ml of culture within 42 hrs, 30 hrs, 25 hrs after incubations of the culture filtrate with the addition of concentration of 1%, 5%, 10%, respectively. The result indicated that the algicidal effect was mediated by certain substances released by Bacillus sp. C-4. The algicides produced by Bacillus sp. C-4 were stable within the pH range of 3~10 and temperature range of 4℃~100℃, respectively.