Mehra Anchal, Garrett Elizabeth M, Serody Christopher J, Tamayo Rita
bioRxiv. 2025 Aug 20:2025.08.20.671228. doi: 10.1101/2025.08.20.671228.
Phase variation of colony morphology occurs via modulation of transcription , which encodes a three-protein signal transduction system. Response regulators CmrR and CmrT promote rough colony development, cell elongation and chaining, surface motility, and disease in the hamster model of infection, while impairing swimming motility and biofilm formation. Using RNA-Seq, we identified the CmrR and CmrT-dependent transcriptional differences in rough and smooth colonies. Further analysis showed that CmrT, but not CmrR, is required for differential expression of most of the genes. Two CmrT-regulated genes, herein named and , were together sufficient for restoring all CmrT-dependent phenotypes in a mutant and alleviating selection of phase ON cells during growth on an agar surface. MrpA and MrpB are uncharacterized proteins with no known function but are highly conserved in . Using immunoprecipitation and mass spectrometry to identify interacting partners, we found that MrpA interacts with the septum-site determining protein MinD and several other proteins involved in cell division and cell shape determination. Ectopic expression of resulted in atypical cell division, consistent with MrpAB interference with MinD function. Our findings reveal a potential mechanism by which phase variation of CmrRST modulates colony morphology and motility: in phase ON cells, CmrT-mediated expression of interferes with normal cell division resulting elongated cells that enable expansion of the population across a surface while limiting swimming motility.
can reversibly switch between two colony morphology variants that differ in multiple additional phenotypes. Previous work determined that the phenotypic switch occurs through phase variation of the CmrRST signal transduction system, however the CmrRST-regulated genes that mediate these phenotypes were unknown. Here, we identified the CmrR- and CmrT-regulated genes that are differentially expressed between rough and smooth colonies and identified two genes, and , that together are sufficient to confer phenotypes associated with expression. Protein interaction studies revealed that MrpA interacts with MinD, a protein that helps ensure symmetric cell division in bacteria. Based on these findings, we propose that MrpA disrupts MinD function leading to aberrant cell division, resulting in elongated cells that form rough colonies. This study reveals previously uncharacterized proteins that affect cell division and broadly impact the physiology of this pathogen.
菌落形态的相变通过转录调控发生，转录编码一个由三种蛋白质组成的信号转导系统。应答调节因子CmrR和CmrT促进粗糙菌落的形成、细胞伸长和连锁、表面运动以及在仓鼠感染模型中的致病作用，同时损害游动运动性和生物膜形成。利用RNA测序，我们确定了粗糙和光滑菌落中CmrR和CmrT依赖性转录差异。进一步分析表明，大多数基因的差异表达需要CmrT而非CmrR。两个受CmrT调控的基因，在此命名为 和 ，共同足以在 突变体中恢复所有CmrT依赖性表型，并在琼脂表面生长期间减轻 相ON细胞的选择。MrpA和MrpB是功能未知的未表征蛋白质，但在 中高度保守。利用免疫沉淀和质谱鉴定相互作用伙伴，我们发现MrpA与隔膜位点决定蛋白MinD以及其他几种参与细胞分裂和细胞形状决定的蛋白质相互作用。 的异位表达导致非典型细胞分裂，这与MrpAB对MinD功能的干扰一致。我们的研究结果揭示了CmrRST相变调节菌落形态和运动性的潜在机制：在相ON细胞中，CmrT介导的 表达干扰正常细胞分裂，导致细胞伸长，使群体能够在表面扩展，同时限制游动运动性。
可以在两种在多种其他表型上不同的菌落形态变体之间可逆切换。先前的工作确定表型转换通过CmrRST信号转导系统的相变发生，然而介导这些表型的CmrRST调控基因尚不清楚。在这里，我们确定了在粗糙和光滑菌落之间差异表达的CmrR和CmrT调控基因，并鉴定了两个基因， 和 ，它们共同足以赋予与 表达相关的表型。蛋白质相互作用研究表明，MrpA与MinD相互作用，MinD是一种有助于确保细菌中对称细胞分裂的蛋白质。基于这些发现，我们提出MrpA破坏MinD功能导致异常细胞分裂，从而产生形成粗糙菌落的伸长细胞。这项研究揭示了以前未表征的影响 细胞分裂并广泛影响该病原体生理学的蛋白质。
