Philips Institute for Oral Health Research, Virginia Commonwealth University School of Dentistry, Richmond, Virginia, USA.
Department of Oral Biology, University of Florida College of Dentistry, Gainesville, Florida, USA.
Mol Microbiol. 2022 Feb;117(2):375-393. doi: 10.1111/mmi.14854. Epub 2021 Dec 18.
Streptococcus sanguinis is an oral commensal and an etiological agent of infective endocarditis. Previous studies have identified the SsaACB manganese transporter as essential for endocarditis virulence; however, the significance of SsaACB in the oral environment has never been examined. Here we report that a ΔssaACB deletion mutant of strain SK36 exhibits reduced growth and manganese uptake under acidic conditions. Further studies revealed that these deficits resulted from the decreased activity of TmpA, shown in the accompanying paper to function as a ZIP-family manganese transporter. Transcriptomic analysis of fermentor-grown cultures of SK36 WT and ΔssaACB strains identified pH-dependent changes related to carbon catabolite repression in both strains, though their magnitude was generally greater in the mutant. In strain VMC66, which possesses a MntH transporter, loss of SsaACB did not significantly alter growth or cellular manganese levels under the same conditions. Interestingly, there were only modest differences between SK36 and its ΔssaACB mutant in competition with Streptococcus mutans in vitro and in a murine oral colonization model. Our results suggest that the heterogeneity of the oral environment may provide a rationale for the variety of manganese transporters found in S. sanguinis.
血链球菌是口腔共生菌和感染性心内膜炎的病原体。先前的研究已经确定 SsaACB 锰转运体对于心内膜炎毒力是必需的；然而，SsaACB 在口腔环境中的意义从未被检验过。在这里，我们报告 SK36 株的ΔssaACB 缺失突变体在酸性条件下表现出生长和锰摄取减少。进一步的研究表明，这些缺陷是由于TmpA 活性降低所致，在随附的论文中证明其作为 ZIP 家族锰转运体发挥作用。SK36 WT 和 ΔssaACB 菌株发酵罐培养的转录组分析鉴定了与两种菌株中碳分解代谢物阻遏相关的 pH 依赖性变化，尽管在突变体中其幅度通常更大。在具有 MntH 转运体的 VMC66 菌株中，在相同条件下，缺失 SsaACB 对生长或细胞锰水平没有显著影响。有趣的是，SK36 及其ΔssaACB 突变体在体外与变形链球菌竞争和在小鼠口腔定植模型中的竞争中仅有适度差异。我们的结果表明，口腔环境的异质性可能为血链球菌中发现的多种锰转运体提供了合理依据。
