Microbes live in complex microniches within host tissues, but how symbiotic partners communicate to create such niches during development remains largely unexplored. Using confocal microscopy and symbiont genetics, we characterized the shaping of host microenvironments during light organ colonization of the squid Euprymna scolopes by the bacterium Vibrio fischeri. During embryogenesis, three pairs of invaginations form sequentially on the organ’s surface, producing pores that lead to interior compressed tubules at different stages of development. After hatching, these areas expand, allowing V. fischeri cells to enter and migrate ∼120 μm through three anatomically distinct regions before reaching blind-ended crypt spaces. A dynamic gatekeeper, or bottleneck, connects these crypts with the migration path. Once V. fischeri cells have entered the crypts, the bottlenecks narrow, and colonization by the symbiont population becomes spatially restricted. The actual timing of constriction and restriction varies with crypt maturity and with different V. fischeri strains. Subsequently, starting with the first dawn following colonization, the bottleneck controls a lifelong cycle of dawn-triggered expulsions of most of the symbionts into the environment and a subsequent regrowth in the crypts. Unlike other developmental phenotypes, bottleneck constriction is not induced by known microbe-associated molecular patterns (MAMPs) or by V. fischeri-produced bioluminescence, but it does require metabolically active symbionts. Further, while symbionts in the most mature crypts have a higher proportion of live cells and a greater likelihood of expulsion at dawn, they have a lower resistance to antibiotics. The overall dynamics of these distinct microenvironments reflect the complexity of the host-symbiont dialogue.

中文翻译：

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共生伙伴之间的相互作用推动了鱿鱼弧菌共生中复杂生物地理学的发展。

微生物生活在宿主组织内的复杂微生态位中，但共生伙伴如何在发育过程中进行交流以形成这样的生态位仍未得到充分的研究。使用共聚焦显微镜和共生遗传学，我们表征了由费氏弧菌对鱿鱼Euprymna瓢虫的轻器官定殖过程中宿主微环境的塑造。在胚胎发生过程中，在器官表面上依次形成三对插入物，产生的毛孔导致在发育的不同阶段产生内部压缩的小管。孵化后，这些区域会扩大，从而允许费氏弧菌细胞进入并迁移穿过三个解剖学上不同的区域约120μm，然后到达盲端隐窝空间。动态的网守或瓶颈将这些加密与迁移路径连接起来。一旦费氏弧菌细胞进入隐窝，瓶颈就变窄，共生菌种群的定居在空间上受到限制。收缩和约束的实际时间随隐窝成熟度和费氏弧菌的不同而变化株。随后，从定居后的第一个黎明开始，瓶颈控制了大多数共生体被黎明触发的驱逐到环境中的终生周期，以及随后的隐窝再生。不像其他的发育表型，瓶颈收缩不通过已知的微生物相关的分子模式（毫安）或通过诱导V.鲵-产生生物发光，但它确实需要代谢活性共生体。此外，尽管最成熟的隐窝中的共生体具有较高的活细胞比例，并且在黎明时被驱逐的可能性更大，但它们对抗生素的抵抗力较低。这些独特的微环境的整体动态反映了主持人共鸣对话的复杂性。