一株溶藻细菌对海洋原甲藻的溶藻效应

从深圳大鹏湾南澳赤潮爆发海域的表层海水中分离得到1株对海洋原甲藻(Prorocentrum micans)具有溶藻活性的海洋细菌,菌株编号为N10。利用液相感染法研究了该溶藻细菌的溶藻效果和溶藻作用方式。结果表明,菌株N10能使藻细胞失去运动活性,并膨胀变形,细胞膜内物质聚集于一端,藻细胞最终破裂死亡。菌悬液接种到藻液中的量越大,初始细菌密度越高,其溶藻效果越强。菌悬液以1∶10的体积比接种到藻液中时,藻细胞在24 h的死亡率为83%,至72 h全部溶解死亡;体积比为1∶20的藻细胞在24 h的死亡率为71%,之后藻细胞密度略有波动,120 h时死亡率达77%;而体积比为1∶100的藻细胞密度在前24 h有所下降,死亡率达39%,之后藻细胞密度又开始明显上升;对照组的藻细胞密度均呈明显上升趋势。菌悬液过滤液和高温加热处理后的菌悬液过滤液对海洋原甲藻均无溶藻活性,表明菌株N10的溶藻方式为直接溶藻。通过16S rRNA序列分析并与GenBank数据进行同源性检索,并结合细菌形态及生理生化特征,菌株N10隶属于黄杆菌科(Flavobacteriaceae)中的Muricauda sp.。

Algicidal activity against Prorocentrum micans by a marine bacterium isolated from a HABs area, South China

Harmful algal blooms (HABs) in coastal waters have made a great negative impact on marine environment and ecosystem, aquaculture industry and human health worldwide. There are a number of strategies that can mitigate HABs, including physical and chemical means, but none of these methods has been totally successful due to the high cost and potential hazard to the aquatic ecosystems. Therefore, it is urgent and beneficial to develop a more economical and environment-friendly algicidal agents to control HABs. It has been reported that certain marine bacteria play an important role in inhibiting the growth of red tide phytoplankton. Many bacterial strains isolated from HABs affected waters have algicidal effects on several HABs species. Thus, the algicidal bacteria could potentially be of great use in HABs controlling. In this paper, a marine algicidal bacterial strain N10 against Prorocentrum micans was isolated from a HABs area in Mirs Bay in south China. The algicidal activity and algicidal mode of strain N10 were tested using 48-well microplate liquid infection methods. Results showed that P. micans which exposed to strain N10 lost its moveability, then inflated and cellular components aggregated, and finally lysed. The algicidal activity was in a concentration-dependent manner. The test of bacterial cultures added to algal cultures at volume ratio of 1: 10 showed the strongest algicidal activity, 83% P. micans lysed within 24 h, and all lysed at 72 h, simultaneously, bacterial density decreased slowly from 7.6×10⁸ CFU/mL to 5.3×10⁸ CFU/mL in 72 h, then decreased sharply to 2.5×10⁶ CFU/mL at 120 h. In the test of 1: 20, 71% P. micans lysed within 24 h, and 77% lysed at the end of 120 h, companied by the bacterial density increasing from 4.0×10⁸ CFU/mL to 5.8×10⁸ CFU/mL within 24 h, then decreasing sharply to 9.0×10⁵ CFU/mL at 120 h. In the test of 1: 100, 39% P. micans lysed within 24 h, then alga cells kept increasing, and only showed a significant inhibiting effect on the growth of alga comparing to that of control test, while the bacterial density decreased sharply from 8.3×10⁷ CFU/mL to 8.8×10⁵ CFU/mL within 48 h, and maintaining at this low density level to the end with 1.2×10⁶ CFU/mL. The density of P. micans exposed to bacterial cultures decreased from (1.75±0.3)×10⁴ cells/mL to (0.53±0.1)×10⁴ cells/mL within 48 h, while that of bacterial culture filtrates, heated bacterial filtrates and control test increased to (4.7±0.2)×10⁴ cells/mL, (5.0±0.6)×10⁴ cells/mL and (5.0±0.3)×10⁴ cells/mL, respectively. It indicated that P. micans lysed by strain N10 in a direct manner. Sequence analysis based on 16S rRNA and performed by BLAST, combined with morphological and physiological biochemical characteristics of bacterium showed the strain N10 belonged to genus of Muricauda sp. in Flavobacteriaceae.