Yang Yuwen, Fei Nuoya, Ji Weiqin, Qiao Pei, Yang Linlin, Liu Dehua, Guan Wei, Zhao Tingchang
State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
National Nanfan Research Institute (Sanya), Chinese Academy of Agricultural Sciences, Sanya 572024, China.
Microorganisms. 2023 Jul 14;11(7):1806. doi: 10.3390/microorganisms11071806.
, the causative agent of bacterial fruit blotch, can be divided into two main groups based on factors such as pathogenicity and host species preference. PilA is an important structural and functional component of type IV pili (T4P). Previous studies have found significant differences in DNA sequences between group I and group II strains of . In this study, we characterized in the group I strain pslb65 and the group II strain Aac5. mutants, complementation strains, and cross-complementation strains were generated, and their biological phenotypes were analyzed to identify functional differences between in the two groups. deletion mutants (pslb65Δ and Aac5Δ) showed significantly reduced pathogenicity compared with the wild-type (WT) strains; pslb65-Δ also completely lost twitching motility, whereas Aac5-Δ only partially lost motility. In King's B medium, there were no significant differences in biofilm formation between pslb65-Δ and WT pslb65, but Aac5-Δ showed significantly reduced biofilm formation compared to WT Aac5. In M9 minimal medium, both mutants showed significantly lower biofilm formation compared to the corresponding WT strains, although biofilm formation was recovered in the complementation strains. The biofilm formation capacity was somewhat recovered in the cross-complementation strains but remained significantly lower than in the WT strains. The interspecies competitive abilities of pslb65-Δ and Aac5-Δ were significantly lower than in the WT strains; Aac5-Δ was more strongly competitive than pslb65-Δ, and the complementation strains recovered competitiveness to WT levels. Furthermore, the cross-complementation strains showed stronger competitive abilities than the corresponding WT strains. The relative expression levels of genes related to T4P and the type VI secretion system were then assessed in the mutants via quantitative PCR. The results showed significant differences in the relative expression levels of multiple genes in pslb65-Δ and Aac5-Δ compared to the corresponding WT stains. This indicated the presence of specific differences in function between the two groups, but the regulatory mechanisms involved require further study.
细菌性果斑病的病原菌可根据致病性和寄主物种偏好等因素分为两个主要组。PilA是IV型菌毛（T4P）的重要结构和功能成分。先前的研究发现，该病原菌I组和II组菌株之间的DNA序列存在显著差异。在本研究中，我们对I组菌株pslb65和II组菌株Aac5进行了特性分析。构建了突变体、互补菌株和交叉互补菌株，并分析了它们的生物学表型，以确定两组中该病原菌的功能差异。与野生型（WT）菌株相比，缺失突变体（pslb65Δ和Aac5Δ）的致病性显著降低；pslb65-Δ也完全丧失了摆动运动能力，而Aac5-Δ仅部分丧失运动能力。在King's B培养基中，pslb65-Δ与WT pslb65之间的生物膜形成没有显著差异，但与WT Aac5相比，Aac5-Δ的生物膜形成显著减少。在M9基本培养基中，与相应的WT菌株相比，两个突变体的生物膜形成均显著降低，尽管互补菌株中生物膜形成有所恢复。交叉互补菌株的生物膜形成能力有所恢复，但仍显著低于WT菌株。pslb65-Δ和Aac5-Δ的种间竞争能力显著低于WT菌株；Aac5-Δ的竞争力比pslb65-Δ更强，互补菌株的竞争力恢复到WT水平。此外，交叉互补菌株表现出比相应WT菌株更强的竞争能力。然后通过定量PCR评估该病原菌突变体中与T4P和VI型分泌系统相关基因的相对表达水平。结果表明，与相应的WT菌株相比，pslb65-Δ和Aac5-Δ中多个基因的相对表达水平存在显著差异。这表明两组该病原菌在功能上存在特定差异，但涉及的调控机制需要进一步研究。
