Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
BMC Microbiol. 2019 Jan 21;19(1):20. doi: 10.1186/s12866-019-1387-9.
The gram-negative Xanthomonas campestris pv. campestris is the pathogenic bacterium that causes black rot disease in crucifers. The virulence determinants of this bacterium include extracellular enzymes, exopolysaccharides, and biofilm formation. Here, one transposon mutant of X. campestris pv. campestris strain 17 that affects biofilm formation was isolated, and subsequent analyses led to the identification of the lolA gene, which encodes an outer membrane lipoprotein chaperone.
The lolA mutant exhibited significant reductions in bacterial attachment, extracellular enzyme production, virulence, and tolerance in the presence of myriad membrane-perturbing agents. These phenotypic changes of the mutant could be complemented to the wild-type level through the intact lolA gene. Proteomic analysis revealed that 109 proteins were differentially expressed after lolA mutation. These differentially expressed proteins were categorized in various functional groups and were mainly associated with the membrane component, were involved in transport, and contained receptor activity. Through reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) analysis, deletion of lolA was determined to have caused significantly reduced expression of genes that encode the major extracellular enzymes, the biofilm-related proteins, and the virulence-related proteins. The RT-qPCR analysis also indicated that the expression of several genes that encode putative outer membrane lipoproteins and TonB-dependent receptors was reduced after lolA mutation.
This is the first report to define the lolA gene as a virulence factor and to contribute to the functional understanding of, and provide new information concerning, the role of lolA in Xanthomonas. Furthermore, the results of this study provide and extend new insights into the function of lolA in bacteria.
革兰氏阴性黄单胞菌（Xanthomonas campestris pv. campestris）是引起十字花科黑腐病的致病菌。该菌的毒力决定因子包括细胞外酶、胞外多糖和生物膜形成。本研究分离到一株影响生物膜形成的黄单胞菌 pv. campestris 17 转座子突变体，并对 lolA 基因进行了鉴定，该基因编码一个外膜脂蛋白伴侣。
LolA 突变体的细菌附着、胞外酶产生、毒力和对多种膜扰动剂的耐受性显著降低。通过完整的 lolA 基因，突变体的这些表型变化可以被互补到野生型水平。蛋白质组学分析显示，lolA 突变后有 109 种蛋白差异表达。这些差异表达的蛋白可分为多个功能组，主要与膜成分相关，参与运输，并具有受体活性。通过反转录定量实时聚合酶链反应（RT-qPCR）分析，发现 lolA 缺失导致编码主要胞外酶、生物膜相关蛋白和毒力相关蛋白的基因表达显著降低。RT-qPCR 分析还表明，lolA 突变后编码假定外膜脂蛋白和 TonB 依赖性受体的几个基因的表达降低。
这是首次将 lolA 基因定义为毒力因子，并有助于对 Xanthomonas 的功能理解，并为 lolA 在黄单胞菌中的作用提供新的信息。此外，本研究的结果为 lolA 在细菌中的功能提供了新的见解并加以扩展。
