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.

蛭弧菌弧菌，属于革兰氏阴性细菌掠夺蛭弧菌和样微生物（BALOs），对革兰阴性菌早。BALO 品系在猎物范围上有所不同，但到目前为止，几乎不了解抵抗 BALO 捕食的遗传基础。我们开发了一种功能丧失方法来筛选 M6 菌株库中的敏感突变体，M6 菌株是植物病原体Acidovorax citrulli 的抗捕食菌株。该屏幕基于跟踪B. bacteriovorus的生长在突变池中表达荧光报告基因 Tdtomato 的菌株，以揭示捕食敏感变体。在对捕食者表现出显着易感性的突变株中鉴定出两个独立的位点。使用蛋白质序列同源性和蛋白质结构模型分析了两个基因座中的基因。两者都是分泌相关蛋白，因此与细菌细胞壁相关。成功互补gspK ，编码未成年pseudopilin蛋白的基因证实了II型分泌系统的参与A. citrulliM6电阻。这一概念验证研究表明，我们的方法可以识别 BALO 与猎物相互作用的关键要素，并验证了单个基因的突变变化可以极大地影响猎物对 BALO 捕食的抵抗力的假设。