Mishra Arunima, Wu Chenggang, Yang Jinghua, Cisar John O, Das Asis, Ton-That Hung
Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX, USAOral Infection and Immunity Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USADepartment of Molecular, Microbial & Structural Biology, University of Connecticut Health Center, Farmington, CT, USA.
Mol Microbiol. 2010 Aug;77(4):841-54. doi: 10.1111/j.1365-2958.2010.07252.x. Epub 2010 Jun 10.
Interbacterial interactions between oral streptococci and actinomyces and their adherence to tooth surface and the associated host cells are key early events that promote development of the complex oral biofilm referred to as dental plaque. These interactions depend largely on a lectin-like activity associated with the Actinomyces oris type 2 fimbria, a surface structure assembled by sortase (SrtC2)-dependent polymerization of the shaft and tip fimbrillins, FimA and FimB respectively. To dissect the function of specific fimbrillins in various adherence processes, we have developed a convenient new technology for generating unmarked deletion mutants of A. oris. Here, we show that the fimB mutant, which produced type 2 fimbriae composed only of FimA, like the wild type co-aggregated strongly with receptor-bearing streptococci, agglutinated with sialidase-treated red blood cells, and formed monospecies biofilm. In contrast, the fimA and srtC2 mutants lacked type 2 fimbriae and were non-adherent in each of these assays. Plasmid-based expression of the deleted gene in respective mutants restored adherence to wild-type levels. These findings uncover the importance of the lectin-like activity of the polymeric FimA shaft rather than the tip. The multivalent adhesive function of FimA makes it an ideal molecule for exploring novel intervention strategies to control plaque biofilm formation.
口腔链球菌与放线菌之间的菌间相互作用及其对牙面和相关宿主细胞的黏附是促进形成称为牙菌斑的复杂口腔生物膜的关键早期事件。这些相互作用很大程度上取决于与口腔放线菌2型菌毛相关的凝集素样活性，菌毛是一种表面结构，分别由分选酶（SrtC2）依赖性的杆状菌毛蛋白FimA和末端菌毛蛋白FimB聚合组装而成。为了剖析特定菌毛蛋白在各种黏附过程中的功能，我们开发了一种便捷的新技术来生成口腔放线菌的无标记缺失突变体。在此，我们表明， fimB突变体产生仅由FimA组成的2型菌毛，与野生型一样，能与携带受体的链球菌强烈共聚集，能与经唾液酸酶处理的红细胞凝集，并形成单菌种生物膜。相比之下， fimA和srtC2突变体缺乏2型菌毛，在上述每种试验中均无黏附能力。在各自的突变体中基于质粒表达缺失的基因可使黏附恢复到野生型水平。这些发现揭示了聚合的FimA杆而非末端的凝集素样活性的重要性。FimA的多价黏附功能使其成为探索控制菌斑生物膜形成新干预策略的理想分子。
