Growth and Genome Features of Non-O1/O139 <i>Vibrio cholerae</i> Isolated from Three Species of Common Freshwater Fish
Xinchi Qin | Lianzhi Yang | Yingwei Xu | Lu Xie | Yongjie Wang | Lanming Chen
<i>Vibrio cholerae</i> is the etiological agent of cholera in humans. The bacterium is frequently detected in aquatic products worldwide. However, the current literature on the genome evolution of <i>V. cholerae</i> of aquatic animal origins is limited. Here, we firstly characterized the growth and genome features of <i>V. cholerae</i> isolates with different resistance phenotypes from three species of common freshwater fish. The results revealed that the non-O1/O139 <i>V. cholerae</i> isolates (<i>n</i> = 4) were halophilic and grew optimally at 2% NaCl and pH 8.0. Their draft genome sequences were 3.89 Mb–4.15 Mb with an average GC content of 47.35–47.63%. Approximately 3366–3561 genes were predicted to encode proteins, but 14.9–17.3% of them were of an unknown function. A number of strain-specific genes (<i>n</i> = 221–311) were found in the four <i>V. cholerae</i> isolates, 3 of which belonged to none of any of the known sequence types (STs). Several putative mobile genetic elements (MGEs) existed in the <i>V. cholerae</i> isolates, including genomic islands (<i>n</i> = 4–9), prophages (<i>n</i> = 0–3), integrons (<i>n</i> = 1–1), and insertion sequences (<i>n</i> = 0–3). Notably, CRISPR-Cas system arrays (<i>n</i> = 2–10) were found in the <i>V. cholerae</i> genomes, whereby the potential immunity defense system could be active. Comparative genomic analyses also revealed many putative virulence-associated genes (<i>n</i> = 106–122) and antibiotic resistance-related genes (<i>n</i> = 6–9). Overall, the results of this study demonstrate the bacterial broader-spectrum growth traits and fill prior gaps in the genomes of <i>V. cholerae</i> originating from freshwater fish.
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