Abstract

The opportunistic pathogen Streptococcus mitis possesses, like other members of the Mitis group of viridans streptococci, phosphorylcholine (P-Cho)-containing teichoic acids (TAs) in its cell wall. Bioinformatic analyses predicted the presence of TAs that are almost identical with those identified in the pathogen Streptococcus pneumoniae, but a detailed analysis of S. mitis lipoteichoic acid (LTA) was not performed to date. Here, we determined the structures of LTA from two S. mitis strains, the high-level beta-lactam and multiple antibiotic resistant strain B6 and the penicillin-sensitive strain NCTC10712. In agreement with bioinformatic predictions, we found that the structure of one LTA (type IV) was like pneumococcal LTA, except the exchange of a glucose moiety with a galactose within the repeating units. Further genome comparisons suggested that the majority of S. mitis strains should contain the same type IV LTA as S. pneumoniae, providing a more complete understanding of the biosynthesis of these P-Cho-containing TAs in members of the Mitis group of streptococci. Remarkably, we observed besides type IV LTA, an additional polymer belonging to LTA type I in both investigated S. mitis strains. This LTA consists of β-galactofuranosyl-(1,3)-diacylglycerol as glycolipid anchor and a poly-glycerol-phosphate chain at the O-6 position of the furanosidic galactose. Hence, these bacteria are capable of synthesizing two different LTA polymers, most likely produced by distinct biosynthesis pathways. Our bioinformatics analysis revealed the prevalence of the LTA synthase LtaS, most probably responsible for the second LTA version (type I), among S. mitis and Streptococcus pseudopneumoniae strains.

中文翻译：

---

共生链球菌产生两种不同的 I 型和 IV 型脂磷壁酸

摘要

与草绿色链球菌的 Mitis 组的其他成员一样，机会性病原体Streptococcus mitis在其细胞壁中具有含磷壁酸 (TAs) 的磷酸胆碱 ( P -Cho)。生物信息学分析预测存在与病原体肺炎链球菌中鉴定的几乎相同的 TA ，但迄今为止尚未对S. mitis lipoteichoic acid (LTA) 进行详细分析。在这里，我们从两个S. mitis确定了 LTA 的结构菌株，高水平β-内酰胺和多重抗生素耐药菌株B6和青霉素敏感菌株NCTC10712。与生物信息学预测一致，我们发现一个 LTA（IV 型）的结构类似于肺炎球菌 LTA，除了重复单元内的葡萄糖部分与半乳糖交换。进一步的基因组比较表明，大多数S. mitis菌株应含有与S. pneumoniae相同的 IV 型 LTA ，从而更全面地了解Mitis 链球菌成员中这些含P -Cho 的 TA 的生物合成。值得注意的是，我们观察到除了 IV 型 LTA 外，还有一种属于 LTA I 型的附加聚合物菌株。该LTA由作为糖脂锚的β-呋喃半乳糖基-(1,3)-二酰基甘油和呋喃半乳糖O -6 位的聚甘油-磷酸链组成。因此，这些细菌能够合成两种不同的 LTA 聚合物，很可能是由不同的生物合成途径产生的。我们的生物信息学分析揭示了 LTA 合酶 LtaS 的流行，它很可能是导致第二个 LTA 版本（I 型）的原因，在S. mitis和Streptococcus pseudopneumoniae菌株中。