Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, PR China.
Vet Microbiol. 2010 Feb 24;141(1-2):149-54. doi: 10.1016/j.vetmic.2009.09.004. Epub 2009 Sep 11.
Edwardsiella tarda is a serious aquaculture pathogen that can infect many cultured fish species. The aim of this study was to investigate the potential importance of DNA adenine methylase (Dam) in E. tarda pathogenesis. The E. tarda dam gene (dam(Et)) was cloned from a pathogenic strain, TXD1, isolated from diseased fish. Dam(Et) shares high (70.2%) sequence identity with the Dam proteins of Yersinia enterocolitica and several other bacterial species. Recombinant Dam(Et) is able to complement a dam-deficient Escherichia coli strain and methylate the genomic DNA. Attenuation of dam(Et) expression by antisense RNA interference had no apparent effect on the growth of TXD1, but caused significant attenuation of overall bacterial virulence and altered several stress responses including spontaneous mutation, recovering from UV radiation and H(2)O(2) exposure, binding to host mucus, and dissemination in host blood and liver. In addition, attenuation of dam(Et) expression increased luxS expression and AI-2 activities in E. tarda. These results indicate that Dam(Et) is a virulence determinant and plays a role in the pathogenesis of TXD1, and that temporal expression of dam(Et) is essential for optimal bacterial infection.
迟缓爱德华氏菌是一种严重的水产养殖病原体，可感染许多养殖鱼类。本研究旨在探讨 DNA 腺嘌呤甲基化酶（Dam）在迟缓爱德华氏菌发病机制中的潜在重要性。从患病鱼类分离的病原菌 TXD1 中克隆了迟缓爱德华氏菌 dam 基因（dam(Et)）。Dam(Et)与肠侵袭性大肠杆菌和其他几种细菌的 Dam 蛋白具有高度的序列同一性（70.2%）。重组 Dam(Et)能够互补 dam 缺陷型大肠杆菌菌株，并使基因组 DNA 甲基化。反义 RNA 干扰对 dam(Et)表达的衰减对 TXD1 的生长没有明显影响，但显著降低了细菌的整体毒力，并改变了几种应激反应，包括自发突变、从 UV 辐射和 H₂O₂暴露中恢复、与宿主粘液结合以及在宿主血液和肝脏中的传播。此外，dam(Et)表达的衰减增加了迟缓爱德华氏菌中 luxS 的表达和 AI-2 活性。这些结果表明，Dam(Et)是一个毒力决定因素，在 TXD1 的发病机制中起作用，并且 dam(Et)的时间表达对于最佳细菌感染是必要的。
