Bacteriophages (phages) are currently available for use by the food industry to control the foodborne pathogen Listeria monocytogenes. Although phage biocontrols are effective under specific conditions, their use can select for phage-resistant bacteria that repopulate phage-treated environments. Here, we performed short-term coevolution experiments to investigate the impact of single phages and a two-phage cocktail on the regrowth of phage-resistant L. monocytogenes and the adaptation of the phages to overcome this resistance. We used whole-genome sequencing to identify mutations in the target host that confer phage resistance and in the phages that alter host range. We found that infections with Listeria phages LP-048, LP-125, or a combination of both select for different populations of phage-resistant L. monocytogenes bacteria with different regrowth times. Phages isolated from the end of the coevolution experiments were found to have gained the ability to infect phage-resistant mutants of L. monocytogenes and L. monocytogenes strains previously found to be broadly resistant to phage infection. Phages isolated from coinfected cultures were identified as recombinants of LP-048 and LP-125. Interestingly, recombination events occurred twice independently in a locus encoding two proteins putatively involved in DNA binding. We show that short-term coevolution of phages and their hosts can be utilized to obtain mutant and recombinant phages with adapted host ranges. These laboratory-evolved phages may be useful for limiting the emergence of phage resistance and for targeting strains that show general resistance to wild-type (WT) phages.

中文翻译：

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选自体外协同进化条件的突变和重组噬菌体克服了噬菌体抗性李斯特菌。

噬菌体（噬菌体）目前可用于食品工业，以控制食源性单核细胞增生李斯特氏菌。尽管噬菌体生物控制在特定条件下是有效的，但它们的使用可以选择重新在噬菌体处理过的环境中繁殖的抗噬菌体细菌。在这里，我们进行了短期的协同进化实验，以研究单一噬菌体和两个噬菌体混合物对噬菌体抗性单核细胞增生李斯特菌的再生和噬菌体适应克服这种抗性的影响。我们使用全基因组测序来鉴定靶宿主中赋予噬菌体抗性的突变和改变宿主范围的噬菌体中的突变。我们发现李斯特菌感染噬菌体LP-048，LP-125或两者的组合针对具有不同再生时间的噬菌体抗性单核细胞增生李斯特菌的不同群体进行选择。发现从协同进化实验结束时分离出的噬菌体具有感染单核细胞增生李斯特菌和单核细胞增生李斯特菌的噬菌体抗性突变体的能力。以前发现它们对噬菌体感染具有广泛的抵抗力。从共感染培养物中分离的噬菌体被鉴定为LP-048和LP-125的重组体。有趣的是，重组事件在编码推测与DNA结合有关的两种蛋白质的基因座中独立发生两次。我们表明，噬菌体及其宿主的短期协同进化可用于获得具有适应宿主范围的突变和重组噬菌体。这些实验室进化的噬菌体可用于限制噬菌体抗性的出现，并靶向显示对野生型（WT）噬菌体具有一般抗性的菌株。