BACKGROUND Phages are thought to play a crucial role in the maintenance of diversity in natural bacterial communities. Theory suggests that phages impose density dependent regulation on bacterial populations, preventing competitive dominants from excluding less competitive species. To test this, we constructed experimental communities containing two bacterial species (Pseudomonas fluorescens and Pseudomonas aeruginosa) and their phage parasites. Communities were propagated at two environmental temperatures that reversed the outcome of competition in the absence of phage. RESULTS The evenness of coexistence was enhanced in the presence of a phage infecting the superior competitor and in the presence of phage infecting both competitors. This occurred because phage altered the balance of competitive interactions through reductions in density of the superior competitor, allowing concomitant increases in density of the weaker competitor. However, even coexistence was not equally stable at the two environmental temperatures. CONCLUSION Phage can alter competitive interactions between bacterial species in a way that is consistent with the maintenance of coexistence. However, the stability of coexistence is likely to depend upon the nature of the constituent bacteria-bacteriophage interactions and environmental conditions.

中文翻译：

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噬菌体对细菌实验种群中种间竞争的影响。

背景技术噬菌体被认为在维持天然细菌群落的多样性中起着至关重要的作用。理论表明，噬菌体对细菌种群施加密度依赖性调节，从而防止竞争优势基因排除竞争性较弱的物种。为了测试这一点，我们构建了包含两个细菌物种（荧光假单胞菌和铜绿假单胞菌）及其噬菌体寄生虫的实验群落。社区在两个环境温度下繁殖，这在缺乏噬菌体的情况下逆转了竞争结果。结果在噬菌体感染优势竞争者和噬菌体感染两个竞争者的情况下，共存的均匀性得到了提高。发生这种情况是因为噬菌体通过降低上等竞争者的密度来改变竞争相互作用的平衡，从而使较弱竞争者的密度随之增加。但是，在两个环境温度下，即使共存也同样不稳定。结论噬菌体可以改变细菌种类之间的竞争性相互作用，与维持共存一致。但是，共存的稳定性可能取决于组成细菌-噬菌体相互作用的性质和环境条件。结论噬菌体可以改变细菌种类之间的竞争性相互作用，与维持共存一致。但是，共存的稳定性可能取决于组成细菌-噬菌体相互作用的性质和环境条件。结论噬菌体可以改变细菌种类之间的竞争性相互作用，与维持共存一致。但是，共存的稳定性可能取决于组成细菌-噬菌体相互作用的性质和环境条件。