School of Physics, Georgia Institute of Technology, Atlanta, GA, USA.
Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA.
J R Soc Interface. 2020 Dec;17(173):20200486. doi: 10.1098/rsif.2020.0486. Epub 2020 Dec 9.
Bacterial communities are governed by a wide variety of social interactions, some of which are antagonistic with potential significance for bacterial warfare. Several antagonistic mechanisms, such as killing via the type VI secretion system (T6SS), require killer cells to directly contact target cells. The T6SS is hypothesized to be a highly potent weapon, capable of facilitating the invasion and defence of bacterial populations. However, we find that the efficacy of contact killing is severely limited by the material consequences of cell death. Through experiments with strains that kill via the T6SS, we show that dead cell debris quickly accumulates at the interface that forms between competing strains, preventing physical contact and thus preventing killing. While previous experiments have shown that T6SS killing can reduce a population of target cells by as much as 10-fold, we find that, as a result of the formation of dead cell debris barriers, the impact of contact killing depends sensitively on the initial concentration of killer cells. Killer cells are incapable of invading or eliminating competitors on a community level. Instead, bacterial warfare itself can facilitate coexistence between nominally antagonistic strains. While a variety of defensive strategies against microbial warfare exist, the material consequences of cell death provide target cells with their first line of defence.
细菌群落受到多种社交互动的影响，其中一些互动具有潜在的细菌战争意义。几种拮抗机制，如通过 VI 型分泌系统（T6SS）进行杀伤，需要杀伤细胞直接接触靶细胞。T6SS 被假设为一种非常有效的武器，能够促进细菌种群的入侵和防御。然而，我们发现，细胞死亡的物质后果严重限制了接触杀伤的效果。通过使用通过 T6SS 进行杀伤的 菌株进行实验，我们表明，死细胞碎片会迅速在竞争菌株形成的界面处积累，阻止物理接触，从而阻止杀伤。虽然之前的实验表明，T6SS 杀伤可以使靶细胞减少多达 10 倍，但我们发现，由于死细胞碎片屏障的形成，接触杀伤的影响对杀伤细胞的初始浓度非常敏感。杀伤细胞无法在群落水平上入侵或消除竞争者。相反，细菌战争本身可以促进名义上拮抗的菌株共存。虽然存在多种针对微生物战争的防御策略，但细胞死亡的物质后果为靶细胞提供了第一道防线。
