Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
Department of Biomedical Informatics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
Infect Immun. 2021 Mar 17;89(4). doi: 10.1128/IAI.00718-20.
Mutation of was previously shown to enhance the virulence of in a murine sepsis model, and this cannot be fully explained by increased expression of genes within the purine biosynthesis pathway. Rather, the increased production of specific virulence factors, including alpha toxin and the fibronectin-binding proteins, was shown to play an important role. Mutation of was also shown previously to result in increased abundance of SarA. Here, we demonstrate by transposon sequencing that mutation of in the USA300 strain LAC increases fitness in a biofilm while mutation of has the opposite effect. Therefore, we assessed the impact of on reported -associated phenotypes by characterizing isogenic , , and mutants. The results confirmed that mutation of results in increased abundance of alpha toxin, protein A, the fibronectin-binding proteins, and SarA, decreased production of extracellular proteases, an increased capacity to form a biofilm, and increased virulence in an osteomyelitis model. Mutation of had the opposite effects on all of these phenotypes and, other than bacterial burdens in the bone, all of the phenotypes of / mutants were comparable to those of mutants. Limiting the production of extracellular proteases reversed all of the phenotypes of mutants and most of those of mutants. We conclude that a critical component defining the virulence of a mutant is the enhanced production of SarA, which limits protease production to an extent that promotes the accumulation of critical virulence factors.
先前的研究表明，突变可增强在小鼠败血症模型中的毒力，而这不能完全用嘌呤生物合成途径中基因表达增加来解释。相反，特定的毒力因子，包括α毒素和纤维连接蛋白结合蛋白的产量增加，被证明起着重要作用。先前的研究还表明，突变会导致 SarA 的丰度增加。在这里，我们通过转座子测序证明，USA300 菌株 LAC 中的突变会增加生物膜中的适应性，而突变则会产生相反的效果。因此，我们通过表征同源的、、和突变体，评估了对报道的与相关表型的影响。结果证实，突变导致α毒素、蛋白 A、纤维连接蛋白结合蛋白和 SarA 的丰度增加，细胞外蛋白酶的产生减少，生物膜形成能力增强，以及在骨髓炎模型中的毒力增加。突变对所有这些表型都有相反的影响，除了骨中的细菌负荷外，/突变体的所有表型都与突变体的表型相当。限制细胞外蛋白酶的产生逆转了突变体的所有表型，并且大部分突变体的表型也被逆转。我们得出的结论是，定义突变体毒力的一个关键因素是 SarA 的产生增强，这在一定程度上限制了蛋白酶的产生，从而促进了关键毒力因子的积累。
