Department of Microbiology, University of Washington, Seattle, WA, USA.
Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA.
Nat Microbiol. 2018 Apr;3(4):440-446. doi: 10.1038/s41564-018-0113-y. Epub 2018 Feb 19.
Bacteria in polymicrobial habitats contend with a persistent barrage of competitors, often under rapidly changing environmental conditions . The direct antagonism of competitor cells is thus an important bacterial survival strategy . 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.
在多微生物栖息地中，细菌面临着持续不断的竞争者的冲击，通常处于快速变化的环境条件下。因此，直接对抗竞争细胞是细菌生存的重要策略。为此，许多细菌物种利用多种具有多种活性的抗菌效应物库；然而，同时部署多种毒素所带来的益处尚不清楚。在这里，我们表明，铜绿假单胞菌的 VI 型分泌系统（T6SS）向竞争细菌输送的多种效应物显示出条件功效，并协同作用。这些效应物之一，Tse4，在高盐环境中活性最高，并与细胞壁降解或细胞内电子载体失活的效应物协同作用。我们发现 Tse4 通过形成破坏质子动力势的ΔΨ 组分的孔来与这些不同的机制协同作用。我们的结果提供了证据，表明同时输送效应物混合物可作为一种风险分散策略，以促进细菌在面对不可预测和多变的环境条件时的竞争力。
