Aharon Einav, Mookherjee Abhirup, Pérez-Montaño Francisco, Mateus da Silva Gustavo, Sathyamoorthy Rajesh, Burdman Saul, Jurkevitch Edouard
Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Institute of Environmental Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food and Environment, The Institute of Environmental Sciences, The Hebrew University of Jerusalem, Rehovot, Israel; Department of Microbiology, University of Seville, Seville, Spain.
Res Microbiol. 2021 Nov-Dec;172(7-8):103878. doi: 10.1016/j.resmic.2021.103878. Epub 2021 Sep 4.
Bdellovibrio bacteriovorus, a Gram-negative predatory bacterium belonging to the Bdellovibrio and like organisms (BALOs), predates on Gram-negative bacteria. BALO strains differ in prey range but so far, the genetic basis of resistance against BALO predation is hardly understood. We developed a loss-of-function approach to screen for sensitive mutants in a library of strain M6, a predation-resistant strain of the plant pathogen Acidovorax citrulli. The screen is based on tracking the growth of a B. bacteriovorus strain expressing the fluorescent reporter Tdtomato in mutant pools to reveal predation-sensitive variants. Two independent loci were identified in mutant strains exhibiting significant levels of susceptibility to the predator. Genes in the two loci were analysed using both protein sequence homology and protein structure modeling. Both were secretion-related proteins and thus associated to the bacterial cell wall. Successful complementation of gspK, a gene encoding for a minor pseudopilin protein confirmed the involvement of the type II secretion system in A. citrulli M6 resistance. This proof of concept study shows that our approach can identify key elements of the BALO-prey interaction, and it validates the hypothesis that mutational changes in a single gene can drastically impact prey resistance to BALO predation.
食菌蛭弧菌是一种革兰氏阴性捕食性细菌，属于蛭弧菌类生物（BALOs），以革兰氏阴性细菌为食。BALO菌株的猎物范围有所不同，但到目前为止，对BALO捕食产生抗性的遗传基础几乎还不清楚。我们开发了一种功能丧失方法，在植物病原菌西瓜嗜酸菌的捕食抗性菌株M6的文库中筛选敏感突变体。该筛选基于追踪在突变体库中表达荧光报告基因Tdtomato的食菌蛭弧菌菌株的生长情况，以揭示捕食敏感变体。在对捕食者表现出显著易感性水平的突变菌株中鉴定出两个独立的基因座。使用蛋白质序列同源性和蛋白质结构建模对这两个基因座中的基因进行了分析。两者都是与分泌相关的蛋白质，因此与细菌细胞壁有关。编码次要假菌毛蛋白的基因gspK的成功互补证实了II型分泌系统参与了西瓜嗜酸菌M6的抗性。这项概念验证研究表明，我们的方法可以识别BALO与猎物相互作用的关键要素，并验证了单个基因突变会极大影响猎物对BALO捕食抗性的假设。
