Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Division of Nephrology, Seirei Hamamatsu General Hospital, Hamamatsu, Japan.
Front Cell Infect Microbiol. 2022 Sep 13;12:994014. doi: 10.3389/fcimb.2022.994014. eCollection 2022.
, a Gram-positive facultative anaerobic bacterium, is a major pathogen of dental caries. The protein Cnm of is involved in collagen binding, but its other biological functions are unknown. In this study, a Cnm-deficient isogenic mutant and a complementation strain were generated from a Cnm-positive strain to help determine the properties of Cnm. Initially, comparison of the cell surface structure was performed by electron microscopy, which demonstrated that Cnm appears to be localized on the cell surface and associated with a protruding cell surface structure. Deep RNA sequencing of the strains revealed that the defect in Cnm caused upregulated expression of many genes related to ABC transporters and cell-surface proteins, while a few genes were downregulated. The amount of biofilm formed by the Cnm-defective strain increased compared with the parental and complemented strains, but the biofilm structure was thinner because of elevated expression of genes encoding glucan synthesis enzymes, leading to increased production of extracellular polysaccharides. Particular antibiotics, including bacitracin and chloramphenicol, had a lower minimum inhibitory concentration for the Cnm-defective strain than particular antibiotics, including bacitracin and chloramphenicol, compared with the parental and complemented strains. Our results suggest that Cnm is located on the cell surface, gives rise to the observed protruding cell surface, and is associated with several biological properties related to membrane permeability.
栖牙密螺旋体是一种革兰氏阳性兼性厌氧菌，是龋齿的主要病原体。 的 Cnm 蛋白参与胶原蛋白结合，但它的其他生物学功能尚不清楚。 在这项研究中，从 Cnm 阳性 菌株中生成了 Cnm 缺失的同基因突变体和互补菌株，以帮助确定 Cnm 的特性。 最初，通过电子显微镜比较细胞表面结构，表明 Cnm 似乎定位于细胞表面并与突出的细胞表面结构相关。 对菌株的深度 RNA 测序表明，Cnm 的缺陷导致与 ABC 转运蛋白和细胞表面蛋白相关的许多基因表达上调，而少数基因表达下调。 与亲本和互补菌株相比，Cnm 缺陷菌株形成的生物膜量增加，但由于编码葡聚糖合成酶的基因表达升高，生物膜结构较薄，导致细胞外多糖产量增加。 与亲本和互补菌株相比，特定抗生素（包括杆菌肽和氯霉素）对 Cnm 缺陷菌株的最低抑菌浓度较低。 我们的结果表明， Cnm 位于细胞表面，产生观察到的突出的细胞表面，并与与膜通透性相关的几种生物学特性相关。
