Department of Biochemistry, University of Madras, Guindy Campus, Chennai, 600025 Tamilnadu, India.
Arch Microbiol. 2010 Aug;192(8):619-23. doi: 10.1007/s00203-010-0588-2. Epub 2010 May 30.
Vibrio shiloi is the first and well-documented bacterium which causes coral bleaching, particularly, during summer, when seawater temperature is between 26 and 31 degrees C. Coral bleaching is the disruption of the symbiotic association between coral hosts and their photosynthetic microalgae zooxanthellae. This is either due to lowered resistance in corals to infection or increased virulence of the bacterium at the higher sea surface temperature. The concentration of the oxygen and resulting oxygen radicals produced by the zooxanthellae during photosynthesis are highly toxic to bacteria, which also assist corals in resisting the infection. Hence, in this study we examined the effect of different temperatures on the activity of a novel extracellular SOD in V. shiloi. We also partially characterized the SOD and clearly confirmed that the extracellular SOD produced by V. shiloi is Mn-SOD type, as it was not inhibited by H2O2 or KCN. Performing chemical susceptibility killing assay, we confirmed that extracellular SOD may act as first line of defense for the bacteria against the reactive oxygen species. Since, increased activity of novel Mn-SOD at higher temperature, leads to the neutralization of radical toxicity and facilitates the survival of V. shiloi. Hence, the extracellular Mn-SOD may be considered as a virulence factor.
希洛弧菌是第一种也是有充分记录的导致珊瑚白化的细菌，特别是在夏季，当海水温度在 26 到 31 摄氏度之间时。珊瑚白化是珊瑚宿主与其光合作用的共生微藻虫黄藻之间共生关系的中断。这要么是由于珊瑚对感染的抵抗力降低，要么是由于更高的海水表面温度导致细菌的毒力增加。虫黄藻在光合作用过程中产生的氧气和由此产生的氧自由基的浓度对细菌具有高度毒性，这也有助于珊瑚抵抗感染。因此，在这项研究中，我们研究了不同温度对希洛弧菌新型细胞外 SOD 活性的影响。我们还对 SOD 进行了部分表征，并明确证实希洛弧菌产生的细胞外 SOD 是 Mn-SOD 型，因为它不受 H2O2 或 KCN 的抑制。通过进行化学敏感性杀伤试验，我们证实细胞外 SOD 可能是细菌对抗活性氧的第一道防线。由于新型 Mn-SOD 在较高温度下的活性增加，导致自由基毒性被中和，并促进了希洛弧菌的存活。因此，细胞外 Mn-SOD 可以被认为是一种毒力因子。
