Department of Microbiology, Soochow University, Taipei 111, Taiwan, ROC.
Int J Food Microbiol. 2010 Feb 28;137(2-3):137-42. doi: 10.1016/j.ijfoodmicro.2009.12.006. Epub 2009 Dec 13.
Vibrio vulnificus is an opportunistic pathogen commonly found in oyster and marine environments, which frequently encounters low salinity stress in its natural and food processing environment. In this study, the responses of a V. vulnificus wild-type strain C78140o and its rpoS isogenic mutant AH1 to sublethal low salinity were examined to investigate the role of rpoS in this response. Both strains, adapted in low salinity (0.4% NaCl), were protected against the lethal low salinity (0.1% NaCl), but were not protected against heat (45 degrees C) or acid stress (pH 3.5), and were sensitized against 5% bile. Protection of the adapted cells against the lethal low salinity was not inhibited by the addition of chloramphenicol. Hemolysis was detected only in the adapted C78140o cells and its spent medium, and was inhibited by chloramphenicol. Transcription of the mechanosensitive channels (VVl_1542 and VVl_2579) and an aquaporin gene (VVl_2010) was markedly increased in the wild-type cells adapted in low salinity medium, while transcription of these genes was slightly enhanced or inhibited in AH1 cells. Results of this study support the active role of rpoS in the low salinity adaptation of V. vulnificus by regulating the expression of virulence and low salinity-associated factors, although rpoS is not related to the immediate protection of the adapted cells against lethal low salinity.
创伤弧菌是一种机会致病菌，常见于牡蛎和海洋环境中，在其自然和食品加工环境中经常遇到低盐度应激。在这项研究中，研究了创伤弧菌野生型菌株 C78140o 和其 rpoS 同源突变体 AH1 对亚致死低盐度的反应，以研究 rpoS 在这种反应中的作用。两种菌株在低盐度（0.4% NaCl）下适应后，均可抵抗致死低盐度（0.1% NaCl），但不能抵抗热（45 摄氏度）或酸应激（pH3.5），并且对 5%胆汁敏感。适应细胞对致死低盐度的保护不受氯霉素的抑制。仅在适应的 C78140o 细胞及其耗尽的培养基中检测到溶血，且氯霉素可抑制溶血。在低盐度培养基中适应的野生型细胞中，机械敏感通道（VVl_1542 和 VVl_2579）和水通道蛋白基因（VVl_2010）的转录明显增加，而 AH1 细胞中这些基因的转录略有增强或抑制。这项研究的结果支持 rpoS 通过调节毒力和低盐度相关因子的表达，在创伤弧菌的低盐度适应中发挥积极作用，尽管 rpoS 与适应细胞对致死低盐度的即时保护无关。
