Coppolino Francesco, Berbiglia Alessia, Lentini Germana, Famà Agata, Pietrocola Giampiero, Teti Giuseppe, Beninati Concetta, De Gaetano Giuseppe Valerio
Department of Human Pathology of Adult and Developmental Age "Gaetano Barresi", University of Messina, 98168 Messina, Italy.
Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy.
Microorganisms. 2024 Oct 20;12(10):2096. doi: 10.3390/microorganisms12102096.
, also known as Group B or GBS, is a commensal colonizer of human vaginal and gastrointestinal tracts that can also be a deadly pathogen for newborns, pregnant women, and the elderly. The SaeRS two-component regulatory system (TCS) positively regulates the expression of two GBS adhesins genes, but its role in the formation of biofilm, an important step in pathogenesis, has not been investigated. In the present study, we set up a novel model of GBS biofilm formation using surfaces coated with human fibrinogen (hFg). Biofilm mass and structure were analyzed by crystal violet staining and three-dimensional fluorescence microscopy, respectively. GBS growth on hFg resulted in the formation of a mature and abundant biofilm composed of bacterial cells and an extracellular matrix containing polysaccharides, proteins, and extracellular DNA (eDNA). Enzymatic and genetic analysis showed that GBS biofilm formation on hFg is dependent on proteins and eDNA in the extracellular matrix and on the presence of covalently linked cell wall proteins on the bacterial surface but not on the type-specific capsular polysaccharide. In the absence of the SaeR regulator of the SaeRS TCS, there was a significant reduction in biomass formation, with reduced numbers of bacterial cells, reduced eDNA content, and disruption of the biofilm architecture. Overall, our data suggest that GBS binding to hFg contributes to biofilm formation and that the SaeRS TCS plays an important role in this process.
B族链球菌（GBS），也称为无乳链球菌，是人类阴道和胃肠道的共生定植菌，但对新生儿、孕妇和老年人来说它也可能是致命病原体。SaeRS双组分调节系统（TCS）正向调节两种GBS黏附素基因的表达，但其在生物膜形成（发病机制中的重要步骤）中的作用尚未得到研究。在本研究中，我们利用包被人纤维蛋白原（hFg）的表面建立了一种GBS生物膜形成的新模型。分别通过结晶紫染色和三维荧光显微镜分析生物膜的质量和结构。GBS在hFg上生长导致形成由细菌细胞和含有多糖、蛋白质及细胞外DNA（eDNA）的细胞外基质组成的成熟且丰富的生物膜。酶学和遗传学分析表明，GBS在hFg上的生物膜形成依赖于细胞外基质中的蛋白质和eDNA以及细菌表面共价连接的细胞壁蛋白的存在，而不依赖于型特异性荚膜多糖。在缺乏SaeRS TCS的SaeR调节因子时，生物量形成显著减少，细菌细胞数量减少，eDNA含量降低，生物膜结构遭到破坏。总体而言，我们的数据表明GBS与hFg的结合有助于生物膜形成，并且SaeRS TCS在此过程中起重要作用。
