Construction of the flagellin F mutant of Vibrio parahaemolyticus and its toxic effects on silver pomfret (Pampus argenteus) cells.

Vibrio parahaemolyticus causes diseases in aquatic organisms, leading to substantial financial losses to the aquaculture industry; its flagellin F (flaF) protein triggers severe inflammation in host cells. To enhance the understanding of the function of flaF in V. parahaemolyticus infection, in this study, a flaF-deficient mutant was constructed by employing two-step homologous recombination. The flaF-deficient mutant induced a significantly lower toll-like receptor 5 (TLR5) expression and apoptosis in fish intestinal epithelial cells than the wild-type V. parahaemolyticus. Furthermore, fluorescence labelling and microscopy analysis of TLR5 showed that V. parahaemolyticus and its mutant strain significantly enhanced TLR5 expression. Additionally, the findings suggest that flaF deletion did not significantly affect the expression of myeloid differentiation factor 88 (MyD88) and interleukin-8 (IL-8) induced by V.parahaemolyticus. In summary, V. parahaemolyticus induced a TLR5-dependent inflammatory response and apoptosis through MyD88, which was observed to be influenced by flaF deletion. In this study, we obtained stable mutants of V. parahaemolyticus via target gene deletion-which is a rapid and effective approach-and compared the induction of inflammatory response and apoptosis by V. parahaemolyticus and its mutant strain, providing novel perspectives for functional gene research in V. parahaemolyticus.

[Multivariate analysis of planktonic Ostracoda communities during autumn and winter in the Beibu Gulf].

Base on the zooplankton samples collected in two cruises for studying the change tendency of ecological environment in the Beibu Gulf, planktonic Ostracoda communities in autumn and winter in the Beibu Gulf were investigated by multivariate analysis. A total of 11 planktonic Ostracoda species were identified and grouped into three ecotypes, i.e., Huposaline and warm-water group, Eurythermal and eurysaline group, as well as Hyperthermal and hysaline group. The average abundance of all species was low, and Euconchoecia aculeate was the most abundant one. Based on the cluster analysis and multidimensional scaling analysis, planktonic Ostracoda in the Beibu Gulf was a community of stable structure, while in autumn and winter, the community also could be divided into two different sub-communities. To understand the relationship between the community structure and the environmental factors, correlation coefficients for the abundance and the environmental factors were calculated. It indicated that water temperature and salinity had tiny impact on planktonic Ostracoda communities, but there was some rule in its change rhythms. Sub-water temperature and salinity had strong impact on community II in winter.