Genome-wide expanding of genetic evolution and potential pathogenicity in <i>Vibrio alginolyticus</i>
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<i>Vibrio alginolyticus</i>, an emergent species of <i>Vibrio</i> genus, exists in aquatic and marine environments. It has undergone genetic diversification, but its detailed genomic diversity is still unclear. Here, we performed a multi-dimensional comparative genomic analysis to explore the population phylogeny, virulence-related genes and potential drug resistance genes of 184 <i>V. alginolyticus</i> isolates. Although genetic diversity is complex, we analysed the population structure using three sub-datasets, including the subdivision for three lineages into sublineages and the distribution of strains in the marine ecological niche. Accessory genes, most of which reclassified <i>V. alginolyticus</i> genomes as different but with relatively close affinities, were nonuniformly distributed among these isolates. We demonstrated that the spread of some post-evolutionary isolates (mainly L3 strains isolated from Chinese territorial seas) was likely to be closely related to human activities, whereas other more ancestral strains (strains in the L1 and L2) tended to be locally endemic and formed clonal complex groups. In terms of pathogenicity, the potential virulence factors were mainly associated with toxin, adherence, motility, chemotaxis, and the type III secretion system (T3SS). We also found five types of antibacterial drug resistance genes. The prevalence of β-lactam resistance genes was 100%, which indicated that there may be a potential risk of natural resistance to β-lactam drugs. Our study reveals insights into genomic characteristics, evolution and potential virulence-associated gene profiles of <i>V. alginolyticus</i>.
溶藻弧菌（Vibrio alginolyticus）是弧菌属（Vibrio）的新兴物种，生存于水生与海洋环境中。该菌已发生遗传分化，但其详细的基因组多样性特征仍未明确。本研究通过多维度比较基因组学分析，对184株溶藻弧菌分离株的种群系统发育、毒力相关基因及潜在耐药基因进行了探究。尽管该菌的遗传多样性较为复杂，本研究借助三个子数据集对其种群结构进行了解析，其中包括将3个进化分支划分为亚分支的分析，以及菌株在海洋生态位中的分布特征。附属基因在这些分离株中呈非均匀分布，这类基因大多可将溶藻弧菌基因组划分为亲缘关系较近的不同类群。研究表明，部分进化后期的分离株（主要为源自中国领海的L3型菌株）的传播可能与人类活动密切相关；而更为古老的菌株（L1与L2型菌株）则多呈地方流行性，并形成了克隆复合群。在致病性方面，潜在毒力因子主要与毒素、黏附、运动、趋化作用以及三型分泌系统（Type III Secretion System, T3SS）相关。本研究还鉴定出5类抗菌药物耐药基因。β-内酰胺类耐药基因的检出率达100%，这提示溶藻弧菌可能存在对β-内酰胺类药物的天然耐药风险。本研究为解析溶藻弧菌的基因组特征、进化过程及潜在毒力相关基因谱提供了新的认知。
