College of Fisheries, Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Research Center for Aquatic Biodiversity Conservation in the Upper Reaches of Yangtze River, Southwest University, Chongqing 400715, China.
College of Fisheries, Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Research Center for Aquatic Biodiversity Conservation in the Upper Reaches of Yangtze River, Southwest University, Chongqing 400715, China.
Int J Biol Macromol. 2024 Aug;274(Pt 2):133270. doi: 10.1016/j.ijbiomac.2024.133270. Epub 2024 Jun 19.
Aeromonas veronii, an opportunistic pathogen, is known to cause serious infections across various species. In our previous study, we discovered that A. veronii GL2 exhibited a virulence up to ten times greater than that of FO1. To ascertain the factors contributing to the disparity in virulence between the two strains, we conducted a comparative transcriptome analysis. This analysis reveals a significant upregulation (P < 0.05) of the ascR gene in GL2 compared with FO1. Additionally, six differentially expressed genes (DEGs) were identified within the "Bacterial secretion system" pathway (map03070), with ascR being an essential component of type III secretion system (T3SS). AscR, considered as SctR family export apparatus subunit within the T3SS, has ambiguous roles in the biological properties, gene expression profiles, virulence and colonization of A. veronii. Therefore, we constructed a mutant strain (ΔascR) by homologous recombination. Comparative analysis with the wide-type GL2 reveals no significant differences in terms of colony morphology, growth curve, hemolytic activity and protease activity. However, significant reductions (P < 0.01) were observed in the abilities of biofilm formation and swimming mobility. No remarkable difference was noted in the lengths of flagella. The LD value of ΔascR was to be 5.15 times higher than that of GL2. Interestingly, the mRNA expression of ascC, ascD, ascJ and ascI genes in the T3SS, and mshB, mshE, mshK and mshP genes in the MSHA type pili were significantly upregulated (P < 0.05) in ΔascR, potentially due to transcriptional compensation. Further analysis of enzymatic biomarkers revealed that ΔascR might not destruct the recognition of innate immune response in host remarkably, but the colonization levels of A.veronii were significantly suppressed (P < 0.01) in ΔascR group. In conclusion, the ascR gene may be a key determinant in regulating the virulence of A. veronii, and the destruction of the T3SS caused by ascR deficiency results in these notable changes.
维氏气单胞菌是一种机会致病菌，已知可导致多种物种的严重感染。在我们之前的研究中，我们发现 A. veronii GL2 的毒力比 FO1 高出十倍。为了确定导致两株菌毒力差异的因素，我们进行了比较转录组分析。该分析表明，与 FO1 相比，GL2 中 ascR 基因的表达显著上调（P < 0.05）。此外，在“细菌分泌系统”途径（map03070）中鉴定出六个差异表达基因（DEGs），其中 ascR 是 III 型分泌系统（T3SS）的必需组成部分。AscR 被认为是 T3SS 中的 SctR 家族输出装置亚基，在 A. veronii 的生物学特性、基因表达谱、毒力和定植中具有模糊的作用。因此，我们通过同源重组构建了突变株（Δ ascR）。与野生型 GL2 的比较分析表明，菌落形态、生长曲线、溶血活性和蛋白酶活性没有显著差异。然而，生物膜形成和泳动能力显著降低（P < 0.01）。鞭毛长度没有明显差异。Δ ascR 的 LD 值是 GL2 的 5.15 倍。有趣的是，T3SS 中的 ascC、ascD、ascJ 和 ascI 基因以及 MSHA 型菌毛中的 mshB、mshE、mshK 和 mshP 基因的 mRNA 表达在Δ ascR 中显著上调（P < 0.05），这可能是由于转录补偿。对酶生物标志物的进一步分析表明，Δ ascR 可能不会显著破坏宿主固有免疫反应的识别，但 A. veronii 的定植水平在Δ ascR 组中显著降低（P < 0.01）。总之，ascR 基因可能是调节 A. veronii 毒力的关键决定因素，ascR 缺失导致 T3SS 破坏，导致这些显著变化。
