Streptococcus parasanguinis is a dominant isolate of dental plaque and an opportunistic pathogen associated with subacute endocarditis. As the expression of collagen binding proteins (CBPs) could promote the establishment of S. parasanguinis in the host, the functions of three putative CBP-encoding loci, Spaf_0420, Spaf_1570, and Spaf_1573, were analyzed using isogenic mutant strains. It was revealed that S. parasanguinis FW213 bound effectively to fibronectin and type I collagen, but the strain’s affinity for laminin and type IV collagen was quite low. By using various deletion derivatives, it was found that these three loci mediated the binding of S. parasanguinis to multiple extracellular matrix molecules, with type I collagen as the common substrate. Derivative strains with a deletion in any of the three loci expressed reduced binding to trypsin-treated swine heart valves. The deletion of these loci also reduced the viable count of S. parasanguinis bacteria within macrophages, especially the loss of Spaf_0420, but only strains with deletions in Spaf_0420 and Spaf_1570 expressed reduced virulence in the Galleria mellonella larva model. The deletion of Spaf_1570 and Spaf_1573 affected mainly the structure, but not the overall mass, of biofilm cultures in a flow cell system. Thus, CBPs are likely to be more critical for the initial colonization of S. parasanguinis on host tissues during the development of endocarditis.

中文翻译：

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副血链球菌 FW213 胶原蛋白结合蛋白的功能分析

副血链球菌是牙菌斑的主要分离株，是与亚急性心内膜炎相关的机会性病原体。由于胶原结合蛋白 (CBP) 的表达可以促进S. parasanguinis在宿主中的建立，因此使用等基因突变株分析了三个假定的 CBP 编码位点 Spaf_0420、Spaf_1570 和 Spaf_1573 的功能。结果表明，S. parasanguinis FW213 与纤连蛋白和 I 型胶原蛋白有效结合，但该菌株对层粘连蛋白和 IV 型胶原蛋白的亲和力非常低。通过使用各种缺失衍生物，发现这三个基因座介导了S. parasanguinis的结合多种细胞外基质分子，以I型胶原蛋白为共同底物。在三个基因座中的任何一个中具有缺失的衍生品系表达与胰蛋白酶处理的猪心脏瓣膜的结合降低。这些基因座的缺失也减少了巨噬细胞内副血链球菌的活菌数，尤其是 Spaf_0420 的缺失，但只有 Spaf_0420 和 Spaf_1570 缺失的菌株在大蜡螟幼虫模型中表现出降低的毒力。Spaf_1570 和 Spaf_1573 的缺失主要影响流动细胞系统中生物膜培养物的结构，但不影响整体质量。因此，在心内膜炎的发展过程中，CBPs可能对S. parasanguinis在宿主组织上的初始定植更为关键。