Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
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DOI：
10.1128/mbio.03060-19
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发表时间：
2020-01-01
期刊：
影响因子：
6.4
通讯作者：
Septer, Alecia N.
中科院分区：
文献类型：
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作者：
Speare, Lauren;Smith, Stephanie;Septer, Alecia N.
共生细菌使用不同的策略来竞争宿主的定殖位点。然而，当细菌在自由生活和与宿主相关的生活方式之间转变时，调节细菌间竞争的环境因素却知之甚少。我们利用Eupyrmna scolopes 鱿鱼和费氏弧菌细菌之间的互利关系来研究当共生体从海水转移到类似宿主的环境时如何调节种内竞争。我们最近报道了 V. fischeri 在宿主定植期间使用 VI 型分泌系统 (T6SS) 进行种内竞争。在这里，我们通过使用模拟粘性宿主环境的液体水凝胶介质研究了环境粘度如何影响 T6SS 介导的竞争。我们的数据表明，尽管当细胞在类似于海水的低粘度液体条件下生长时，T6SS 在功能上不活跃，但暴露于类似宿主的高粘度水凝胶会增强 T6SS 表达和鞘形成，在短短 30 分钟内激活 T6SS 介导的杀伤，并促进竞争基因型的共聚集。最后，基于质谱的蛋白质组学的使用揭示了细胞如何在栖息地转变期间为 T6SS 竞争做好准备的见解。这些发现建立了使用新的水凝胶培养条件来研究 T6SS 相互作用的方法，表明费氏弧菌快速响应物理环境，激活宿主定植期间使用的竞争机制。 重要性 细菌经常参与干扰竞争，以获得进入生态位的机会，例如宿主。然而，人们对自由生活或宿主相关细菌所经历的物理环境如何影响这种竞争知之甚少。我们使用生物发光鱿鱼共生体费氏弧菌来研究环境粘度如何影响细菌竞争。我们的结果表明，从浮游环境过渡到类宿主环境时，费氏弧菌细胞会激活其 VI 型分泌系统（一种依赖于接触的细菌间纳米武器），以消除天然竞争者。这项工作表明，竞争细胞在类似宿主的条件下形成聚集体，从而促进杀伤所需的接触，并揭示了费氏弧菌如何调节响应物理环境的关键竞争机制。
Symbiotic bacteria use diverse strategies to compete for host colonization sites. However, little is known about the environmental cues that modulate interbacterial competition as they transition between free-living and host-associated lifestyles. We used the mutualistic relationship between Eupyrmna scolopes squid and Vibrio fischeri bacteria to investigate how intraspecific competition is regulated as symbionts move from the seawater to a host-like environment. We recently reported that V. fischeri uses a type VI secretion system (T6SS) for intraspecific competition during host colonization. Here, we investigated how environmental viscosity impacts T6SS-mediated competition by using a liquid hydrogel medium that mimics the viscous host environment. Our data demonstrate that although the T6SS is functionally inactive when cells are grown under low-viscosity liquid conditions similar to those found in seawater, exposure to a host-like high-viscosity hydrogel enhances T6SS expression and sheath formation, activates T6SS-mediated killing in as little as 30 min, and promotes the coaggregation of competing genotypes. Finally, the use of mass spectrometry-based proteomics revealed insights into how cells may prepare for T6SS competition during this habitat transition. These findings, which establish the use of a new hydrogel culture condition for studying T6SS interactions, indicate that V. fischeri rapidly responds to the physical environment to activate the competitive mechanisms used during host colonization.IMPORTANCE Bacteria often engage in interference competition to gain access to an ecological niche, such as a host. However, little is known about how the physical environment experienced by free-living or host-associated bacteria influences such competition. We used the bioluminescent squid symbiont Vibrio fischeri to study how environmental viscosity impacts bacterial competition. Our results suggest that upon transition from a planktonic environment to a host-like environment, V. fischeri cells activate their type VI secretion system, a contact-dependent interbacterial nanoweapon, to eliminate natural competitors. This work shows that competitor cells form aggregates under host-like conditions, thereby facilitating the contact required for killing, and reveals how V. fischeri regulates a key competitive mechanism in response to the physical environment.