Pathogens and Disease Transfer, Institute of Marine Research, Bergen, Norway.
J Fish Dis. 2022 Sep;45(9):1373-1388. doi: 10.1111/jfd.13668. Epub 2022 Jun 23.
Bacterial mutation and genetic diversity in aquaculture have led to increasing phenotypic variances, which can weaken or invalidate strategies for controlling diseases. However, few studies have monitored the degree of mutation in fish bacterial pathogens caused by environmental pressure within a short period. In this study, transcriptomic sequences from Edwardsiella piscicida, Vibrio harveyi and Streptococcus parauberis under stressed environments were used for investigating the emergence of variants. In detail, a sub-inhibitory concentration of formalin and phenol for E. piscicida, sea water at 30°C for V. harveyi and flounder serum for S. parauberis were used as stressed environments, and significant single-nucleotide polymorphisms (SNPs) and/or mutation sites were investigated after culture in the ordinary liquid media (control) and the stressed environment through a genome-wide association study. As results, several SNPs or mutations during incubation were observed under different environments in E. piscicida and/or V. harveyi in the genes relevant to flagella, fimbria type 3 secretion systems, and outer and inner membranes that have been directly exposed to external environments. In particular, given that flagella and fimbriae are considered important factors in differentiating the serotypes in some bacterial pathogens, it can be speculated that different environmental pressures are the source of phenotypic or serotypic differentiation from the same origin. On the other hands, S. parauberis did not exhibit notable changes for 4 h when inoculated in the serum from olive flounder. The results presented in this study provide examples of possible molecular evolution in pathogens relevant to the aquaculture industry as a response to different environmental pressure.
水产养殖中的细菌突变和遗传多样性导致表型变异增加，这可能削弱或使控制疾病的策略无效。然而，很少有研究监测在短时间内鱼类细菌病原体因环境压力而发生突变的程度。在这项研究中，使用爱德华氏菌、哈维氏弧菌和无乳链球菌在应激环境下的转录组序列来研究变异体的出现。详细地说，亚抑菌浓度的福尔马林和苯酚用于爱德华氏菌，30°C 的海水用于哈维氏弧菌，牙鲆血清用于无乳链球菌作为应激环境，通过全基因组关联研究，在普通液体培养基（对照）和应激环境中培养后，研究了与鞭毛、III 型菌毛分泌系统以及直接暴露于外部环境的外膜和内膜相关的基因中的显著单核苷酸多态性（SNP）和/或突变位点。结果表明，在爱德华氏菌和/或哈维氏弧菌的基因中，在不同环境下孵育过程中观察到了几个与鞭毛、III 型菌毛分泌系统以及外膜和内膜相关的 SNP 或突变，这些基因直接暴露于外部环境。特别是，由于鞭毛和菌毛被认为是一些细菌病原体血清型分化的重要因素，可以推测不同的环境压力是同一来源的表型或血清型分化的来源。另一方面，当在橄榄牙鲆血清中接种时，无乳链球菌在 4 小时内没有表现出明显的变化。本研究的结果提供了水产养殖相关病原体在应对不同环境压力时可能发生分子进化的实例。
