Data from: Parasites and competitors suppress bacterial pathogen synergistically due to evolutionary trade-offs

Parasites and competitors are important for regulating pathogen densities and subsequent disease dynamics. It is, however, unclear to what extent this is driven by ecological and evolutionary processes. Here we used experimental evolution to study the eco-evolutionary feedbacks between Ralstonia solanacearum bacterial pathogen, Ralstonia-specific phage parasite and Bacillus amyloliquefaciens competitor bacterium in the laboratory and plant rhizosphere. We found that while the phage had a small effect on pathogen densities on its own, it considerably increased the R. solanacearum sensitivity to antibiotics produced by B. amyloliquefaciens. Instead of density effects, this synergy was due to phage-driven increase in phage resistance that led to trade-off with the resistance to B. amyloliquefaciens antibiotics. While no evidence was found for pathogen resistance evolution to B. amyloliquefaciens antibiotics, the fitness cost of adaptation (reduced growth) was highest when the pathogen had evolved in the presence of both parasite and competitor. Qualitatively similar patterns were found between laboratory and greenhouse experiments even though the evolution of phage resistance was considerably attenuated in the tomato rhizosphere. These results suggest that evolutionary trade-offs can impose strong constraints on disease dynamics and that combining phages and antibiotic-producing bacteria could be an efficient way to control agricultural pathogens.

寄生生物与竞争微生物对于调控病原物密度及后续病害动态具有重要意义。然而，目前尚不清楚该调控作用在多大程度上由生态过程与进化过程共同驱动。
本研究采用实验进化(experimental evolution)方法，在实验室体系与植物根际(rhizosphere)环境中，探究了细菌性病原物青枯雷尔氏菌(Ralstonia solanacearum)、其专一性寄生噬菌体(phage)以及竞争细菌解淀粉芽孢杆菌(Bacillus amyloliquefaciens)三者之间的生态-进化反馈(eco-evolutionary feedbacks)关系。
研究结果显示，尽管噬菌体单独作用时对病原物密度的影响微弱，但其可显著提升青枯雷尔氏菌对解淀粉芽孢杆菌所产抗生素的敏感性。该协同效应并非通过改变病原物密度实现，而是源于噬菌体诱导的噬菌体抗性增强——这一变化使得青枯雷尔氏菌在解淀粉芽孢杆菌抗生素抗性方面产生了适合度权衡(trade-off)。
尽管未发现病原物对解淀粉芽孢杆菌抗生素产生抗性进化的证据，但当病原物同时暴露于寄生噬菌体与竞争细菌时，其适应性的适合度代价(fitness cost，即生长速率降低)最为显著。
尽管在番茄根际环境中噬菌体抗性的进化程度显著减弱，但实验室体系与温室试验中观测到的变化模式在定性上保持一致。
本研究结果表明，进化权衡可对病害动态施加较强的约束作用，而将噬菌体与产抗生素细菌联合使用，有望成为防控农业病原物的高效策略。