Bacteria in polymicrobial habitats contend with a persistent barrage of competitors, often under rapidly changing environmental conditions ¹ . The direct antagonism of competitor cells is thus an important bacterial survival strategy ² . Towards this end, many bacterial species employ an arsenal of antimicrobial effectors with multiple activities; however, the benefits conferred by the simultaneous deployment of diverse toxins are unknown. Here we show that the multiple effectors delivered to competitor bacteria by the type VI secretion system (T6SS) of Pseudomonas aeruginosa display conditional efficacy and act synergistically. One of these effectors, Tse4, is most active in high-salinity environments and synergizes with effectors that degrade the cell wall or inactivate intracellular electron carriers. We find Tse4 synergizes with these disparate mechanisms by forming pores that disrupt the ΔΨ component of the proton motive force. Our results provide evidence that the concomitant delivery of a cocktail of effectors serves as a bet-hedging strategy to promote bacterial competitiveness in the face of unpredictable and variable environmental conditions.

中文翻译：

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条件毒性和协同作用推动了抗菌效应物的多样性。

多微生物栖息地中的细菌经常在快速变化的环境条件下¹与持续不断的竞争者抗衡。因此，直接拮抗竞争细胞是一种重要的细菌生存策略². 为此，许多细菌物种采用了具有多种活性的抗菌效应器库；然而，同时部署多种毒素所带来的好处尚不清楚。在这里，我们显示通过铜绿假单胞菌的 VI 型分泌系统 (T6SS) 传递给竞争细菌的多种效应器显示出条件功效并协同作用。其中一种效应器 Tse4 在高盐度环境中最为活跃，并与降解细胞壁或使细胞内电子载体失活的效应器协同作用。我们发现 Tse4 通过形成破坏质子动力的 ΔΨ 分量的孔隙与这些不同的机制协同作用。