Bacterial communities are often highly diverse with several closely related species (or strains) coexisting together. These bacteria compete for resources and the competitive exclusion principle predicts that all but the fastest-growing bacteria will go extinct. When exposed to phage, it is predicted that bacterial strains with restriction-modification (RM) systems can circumvent the competitive exclusion principle and reach diversity on the order of the phage burst size. We show that with a trade-off between bacterial growth rates and the strength of their RM systems, the diversity of such an ecosystem can further increase several fold beyond the burst size limit. Moreover, we find that the ratio of the growth rate of a bacterial strain to the imperfection of its RM system is an excellent predictor of (i) whether the strain will go extinct or not, and (ii) the biomass of the strain if it survives. In contrast, the growth rate alone is not a determinant of either of these properties. Our work provides a quantitative example of a model ecosystem where the fitness of a species is determined not by growth rate, but by a trade-off between growth and defence against predators.

中文翻译：

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在敌对世界中防御与增长-噬菌体和细菌的教训

细菌群落通常高度多样性，几个紧密相关的物种（或菌株）并存。这些细菌争夺资源，竞争排斥原理预测，除了增长最快的细菌之外，所有细菌都将灭绝。当暴露于噬菌体时，可以预见具有限制性修饰（RM）系统的细菌菌株可以规避竞争排斥原理，并且可以达到噬菌体爆发量级的多样性。我们表明，在细菌生长速率与其RM系统强度之间进行权衡时，这种生态系统的多样性可以进一步增加超过爆发大小限制的几倍。此外，我们发现细菌菌株的生长速率与其RM系统缺陷之间的比率是（i）该菌株是否会灭绝的极佳预测指标，（ii）菌株的生物量（如果存活）。相反，仅增长率不是决定这些特性中的任一个。我们的工作提供了一个模型生态系统的定量示例，其中物种的适应性不是由增长率决定，而是由生长与对天敌的防御之间的权衡决定。