Conflicting selection alters the trajectory of molecular evolution in a tripartite bacteria–plasmid–phage interaction

Bacteria engage in a complex network of ecological interactions, which includes mobile genetic elements (MGEs) such as phages and plasmids. These elements play a key role in microbial communities as vectors of horizontal gene transfer but can also be important sources of selection for their bacterial hosts. In natural communities, bacteria are likely to encounter multiple MGEs simultaneously and conflicting selection among MGEs could alter the bacterial evolutionary response to each MGE. Here, we test the effect of interactions with multiple MGEs on bacterial molecular evolution in the tripartite interaction between the bacterium, Pseudomonas fluorescens, the lytic bacteriophage, SBW25φ2, and conjugative plasmid, pQBR103, using genome sequencing of experimentally evolved bacteria. We show that individually, both plasmids and phages impose selection leading to bacterial evolutionary responses that are distinct from bacterial populations evolving without MGEs, but that together, plasmids ...细菌参与构成复杂的生态互作网络，该网络包含噬菌体、质粒等可移动遗传元件（mobile genetic elements, MGEs）。这类元件作为水平基因转移的载体，在微生物群落中发挥关键作用，同时也可成为其细菌宿主的重要选择压力来源。在自然群落中，细菌往往会同时接触多种可移动遗传元件，而不同可移动遗传元件间的选择压力冲突，可能会改变细菌对每种元件的进化响应。本研究以实验进化菌株的基因组测序数据为基础，针对荧光假单胞菌（Pseudomonas fluorescens）、裂解性噬菌体SBW25φ2与接合性质粒pQBR103之间的三方互作体系，探究多种可移动遗传元件的互作对细菌分子进化的影响。研究结果表明，质粒与噬菌体单独存在时均会施加选择压力，使细菌产生的进化响应与未接触可移动遗传元件的细菌种群显著不同；而当二者共存时，质粒……