Physiological Heterogeneity Triggers Sibling Conflict Mediated by the Type VI Secretion System in an Aggregative Multicellular Bacterium.
Physiological Heterogeneity Triggers Sibling Conflict Mediated by the Type VI Secretion System in an Aggregative Multicellular Bacterium.
复制标题
生理异质性引发聚集性多细胞细菌中 VI 型分泌系统介导的兄弟冲突。
作者：
Troselj,Vera;Treuner-Lange,Anke;Søgaard-Andersen,Lotte;Wall,Daniel
社会微生物的一个标志是它们能够参与复杂和协调的行为，这些行为取决于许多细胞之间的合作和同步行动。例如，粘细菌使用聚集策略来形成多细胞，充满孢子的子实体以应对饥饿。同步化过程的一个障碍是克隆种群内的生理异质性。粘细菌如何科普这些生理差异知之甚少。在这里，我们研究了密切相关，但生理上不同的Myxococcus xanthuspopulations之间的相互作用。我们使用遗传方法来创建氨基酸营养缺陷型，并测试它们如何与亲本原养型菌株相互作用。重要的是，我们发现，营养缺陷型被杀死时，前者是饥饿的氨基酸，但不是当生长在丰富的培养基或当两个菌株饥饿的原养型兄弟。这种拮抗作用依赖于VI型分泌系统（T6 SS）以及滑行运动;特别是，我们确定了效应免疫对（TsxEI）作为这种杀伤的介质。这种同胞拮抗作用是由于饥饿人群中TsxI免疫蛋白水平较低所致。因此，当饥饿的营养缺陷型与非饥饿的原养型混合时，营养缺陷型容易受到由T6 SS从原养型递送的TsxE效应物的毒害。此外，我们的研究结果表明，均匀饥饿的人口减少T6 SS的活性，因此，不相互拮抗。我们得出结论，异质种群ofM. xanthususe T6 SS依赖性杀伤消除饥饿或不太适合的细胞，从而促进实现人口内的稳态和同步的behaviors.IMPORTANCESocial细菌采用精心设计的战略，以适应环境的挑战。为不可预测的变化做准备的一种方法是让克隆种群包含具有不同生理状态的个体。这些亚群将对新的环境条件做出不同的反应，确保某些细胞能够更好地适应。然而，对于社会性细菌，生理异质性可能会阻碍克隆种群同步其行为的能力。通过使用一种高度合作和同步的模式生物，M. xanthus，我们询问了相互作用的兄弟姐妹之间的生理差异如何影响他们的集体行为。生理异质性的实验设计，使一个人口饥饿，而其他增长时混合。我们发现，这些差异导致了社会冲突，更健康的个体杀死了他们不太健康的兄弟姐妹。这是第一次，我们报告说，T6 SS的粘细菌介导的兄弟姐妹之间的拮抗作用，导致粘细菌种群变得更加同步进行社会行为。
A hallmark of social microorganisms is their ability to engage in complex and coordinated behaviors that depend on cooperative and synchronized actions among many cells. For instance, myxobacteria use an aggregation strategy to form multicellular, spore-filled fruiting bodies in response to starvation. One barrier to the synchronization process is physiological heterogeneity within clonal populations. How myxobacteria cope with these physiological differences is poorly understood. Here, we investigated the interactions between closely related but physiologically distinctMyxococcus xanthuspopulations. We used a genetic approach to create amino acid auxotrophs and tested how they interact with a parental prototroph strain. Importantly, we found that auxotrophs were killed by their prototroph siblings when the former were starved for amino acids but not when grown on rich medium or when both strains were starved. This antagonism depended on the type VI secretion system (T6SS) as well as gliding motility; in particular, we identified the effector-immunity pair (TsxEI) as the mediator of this killing. This sibling antagonism resulted from lower levels of the TsxI immunity protein in the starved population. Thus, when starving auxotrophs were mixed with nonstarving prototrophs, the auxotrophs were susceptible to intoxication by the TsxE effector delivered by the T6SS from the prototrophs. Furthermore, our results suggested that homogeneously starving populations have reduced T6SS activity and, therefore, do not antagonize each other. We conclude that heterogeneous populations ofM. xanthususe T6SS-dependent killing to eliminate starving or less-fit cells, thus facilitating the attainment of homeostasis within a population and the synchronization of behaviors.IMPORTANCESocial bacteria employ elaborate strategies to adapt to environmental challenges. One means to prepare for unpredictable changes is for clonal populations to contain individuals with diverse physiological states. These subpopulations will differentially respond to new environmental conditions, ensuring that some cells will better adapt. However, for social bacteria physiological heterogeneity may impede the ability of a clonal population to synchronize their behaviors. By using a highly cooperative and synchronizable model organism,M. xanthus, we asked how physiological differences between interacting siblings impacted their collective behaviors. Physiological heterogeneity was experimentally designed such that one population starved while the other grew when mixed. We found that these differences led to social conflict where more-fit individuals killed their less-fit siblings. For the first time, we report that the T6SS nanoweapon mediates antagonism between siblings, resulting in myxobacterial populations becoming more synchronized to conduct social behaviors.