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Understanding the mechanisms of intracellular filamentation by bacteria

了解细菌细胞内丝状化的机制

基本信息

批准号：
10673747
负责人：
Robert J Luallen
金额：
$ 37.63万
依托单位：
SAN DIEGO STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2022
资助国家：
美国
起止时间：
2022-08-01 至 2027-07-31
项目状态：
未结题

项目摘要

PROJECT SUMMARY Bacteria often change their cell shape as a fitness strategy to survive or thrive in diverse environments. Filamentation is one such morphological strategy, whereby a bacterium dramatically increases in cell size as it undergoes longitudinal growth without septation. Many bacteria have been observed to undergo filamentation, but the purpose of these filaments in a host animal is often unknown and the genetic mechanisms governing this morphological change are largely understudied, outside of the canonical SOS response. This proposal utilizes an innovative model system to study bacterial filamentation in the context of a host animal, which consists of a facultative intracellular bacterium, Bordetella atropi, that filaments in the genetic model organisms Oscheius tipulae and Caenorhabditis elegans. Strikingly, B. atropi uses filamentation as an adaptive response to nutrients for cell-to-cell spreading: after invasion of an intestinal epithelial cell, B. atropi converts from a coccobacillus to a filamentous morphology and these filaments invade multiple neighboring epithelial cells. This filamentation by B. atropi was found to be independent of the canonical SOS response but required a conserved nutrient-sensing pathway, the glucolipid pathway, which produces and utilizes the bacterial metabolite UDP-glucose. Divergent bacteria use the glucolipid pathway to detect rich culture conditions and delay the divisome resulting in moderately larger progeny after binary division. Taken together, these discoveries suggest that B. atropi detects the rich intracellular environment of its host cell to trigger filamentation, allowing it to invade neighboring cells. This proposal will further elucidate the mechanism that the glucolipid pathway uses to inhibit the bacterial divisome and initiate filamentation, uncover the role that host metabolites play in triggering the phenotype, and discover other genes/pathways controlling intracellular filamentation by bacteria. First, the genetic mechanism that glucolipid pathway members use to constitutively inhibit septation will be investigated in B. atropi and this pathway will be tested in related bacterial species for a role in controlling filamentation. Second, given that the glucolipid pathway can delay binary division in bacteria grown on rich media, B. atropi will be tested for dependency on host glucose levels and a rich intracellular environment to induce filamentation. Finally, a transposon mutagenesis screen will identify a majority of bacterial genes required for intracellular filamentation in O. tipulae. The results established here will serve as a technical roadmap for determining whether other bacteria can use the glucolipid pathway or other novel genetic pathways to induce filamentation. Given the importance of filamentation to bacterial function and survival in a variety of niches, including in the context of a host animal, this work will increase our understanding of both the environmental triggers and genetic mechanisms that lead this vital morphological change.

项目概要细菌经常改变其细胞形状，作为在不同环境中生存或繁衍的适应性策略。丝状形成就是这样一种形态学策略，细菌的细胞大小急剧增加，如下所示：它经历纵向生长而没有分隔。人们观察到许多细菌会经历丝状形成，但这些丝在宿主动物中的用途通常是未知的，并且遗传因素除了规范的 SOS 之外，控制这种形态变化的机制在很大程度上还没有得到充分研究回复。该提案利用创新的模型系统来研究细菌丝状化宿主动物，由兼性细胞内细菌阿托氏博德特氏菌（Bordetella atropi）组成，该细菌在遗传模型生物Oscheius Tipulae 和Caenorhabditis elegans。引人注目的是，B. atropi 使用丝状形成是细胞间传播对营养物质的适应性反应：入侵肠道后在上皮细胞中，阿托皮芽孢杆菌从球杆菌转变为丝状形态，并且这些丝侵入多个邻近的上皮细胞。发现阿托皮芽孢杆菌的这种丝化独立于典型的 SOS 反应，但需要一条保守的营养感应途径，即糖脂途径，产生并利用细菌代谢物UDP-葡萄糖。不同的细菌利用糖脂途径检测丰富的培养条件并延迟分裂，从而在二元后产生稍大的后代分配。总而言之，这些发现表明阿托品芽孢杆菌检测到了丰富的细胞内环境它的宿主细胞触发丝状化，使其能够侵入邻近的细胞。该提案将进一步阐明糖脂途径用于抑制细菌分裂体并启动丝状化的机制，揭示宿主代谢物在触发表型中所起的作用，并发现其他基因/途径通过细菌控制细胞内丝状化。一、糖脂途径的遗传机制将在阿托皮芽孢杆菌中研究用于组成性抑制分隔的成员，并将测试该途径在相关细菌物种中具有控制丝状形成的作用。其次，糖脂途径可以延迟在富培养基上生长的细菌的二元分裂，将测试阿托皮芽孢杆菌对宿主的依赖性葡萄糖水平和丰富的细胞内环境可诱导丝状形成。最后，转座子诱变筛选将鉴定 O.tipulae 细胞内丝状化所需的大多数细菌基因。这这里建立的结果将作为确定其他细菌是否可以使用该技术的技术路线图糖脂途径或其他新的遗传途径来诱导丝状化。鉴于重要性丝状化对细菌功能和各种生态位中的生存，包括在宿主动物的环境中，这项工作将增进我们对环境触发因素和遗传机制的理解导致这一重要的形态变化。