Vibrio plasmids harboring vhv gene associated with shrimp translucent post-larvae disease: Coexistence of two types of T4SS and multiple transposons.

Translucent post-larvae disease (TPD), known as "glass post-larvae disease" is an emerging threat characterized by high mortality rates and severe economic losses. The pathogenesis of TPD has been linked to the Vibrio high virulent (vhv) gene by virulent strains of V. parahaemolyticus. This study presents a comparative genomic analysis of 16 Vibrio plasmids carrying the vhv gene, associated with TPD in shrimp. Specifically, the analysis identified secretion systems and transposons within these plasmids, revealing that all 16 harbor the Type IV Secretion System (T4SS), with distinct T4SS_typeT and T4SS_typeF gene clusters in seven and nine plasmids, respectively. And it was found that the two types of plasmids can coexist within a single bacterial strain. A diverse array of transposons, classified into seven families, was also identified. The study unveils the genetic intricacies of two plasmid types carrying the vhv gene, which are implicated in TPD pathogenesis. The findings underscore the importance of these plasmids' classification based on their secretion systems and highlight their genetic diversity and the presence of transposons, key factors in bacterial adaptability and virulence. This understanding is crucial for developing strategies to mitigate TPD's impact on shrimp aquaculture and ensure food safety.