Deficiency of RgpG Causes Major Defects in Cell Division and Biofilm Formation, and Deficiency of LytR-CpsA-Psr Family Proteins Leads to Accumulation of Cell Wall Antigens in Culture Medium by Streptococcus mutans
Deficiency of RgpG Causes Major Defects in Cell Division and Biofilm Formation, and Deficiency of LytR-CpsA-Psr Family Proteins Leads to Accumulation of Cell Wall Antigens in Culture Medium by Streptococcus mutans
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DOI：
10.1128/aem.00928-17
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发表时间：
2017-09-01
影响因子：
4.4
通讯作者：
Wen, Zezhang T.
中科院分区：
文献类型：
--
作者：
De, Arpan;Liao, Sumei;Wen, Zezhang T.
已知变形链球菌拥有鼠李糖-葡萄糖多糖（RGP），一种主要的细胞壁抗原。通过等位基因交换构建了编码 RGP 生物合成途径第一种酶的 rgpG 缺陷的变形链球菌菌株。 rgpG 缺乏对生长速度没有影响，但会导致细胞分裂的重大缺陷和细胞形态的改变。与球状野生型不同，rgpG 突变体主要存在于肿胀的“方形”分裂细胞链中。 rgpG 缺乏也会导致生物膜形成显着减少 (P < 0.01)。使用 rgpG 突变体构建了 brpA 和/或 psr 缺陷的双突变体和三突变体，编码 LytR-CpsA-Psr 家族蛋白 BrpA 和 Psr 的基因先前已被证明在细胞被膜生物发生中发挥重要作用。野生型菌株与rgpG brpA和rgpG psr双突变体的生长速率没有显着差异，但rgpG brpA psr三突变体的生长速率急剧降低（P < 0.001）。在透射电子显微镜下，两个双突变体都类似于rgpG突变体，而三重突变体则以具有多个不对称隔膜的巨细胞形式存在。通过免疫印迹分析时，与野生型相比，rgpG 突变体显示细胞壁抗原显着减少，而双突变体和三突变体以及 brpA 和 psr 单突变体检测到很少或没有信号。这些结果表明，变形链球菌中的 RgpG 在细胞分裂和生物膜形成中起着关键作用，并且 BrpA 和 Psr 可能负责将细胞壁抗原附着到细胞包膜上。 重要性 变形链球菌是人类龋齿的主要病原体，产生鼠李糖-葡萄糖多糖 (RGP) 作为主要细胞壁抗原。这项研究提供了直接证据，表明 RGP 生物合成途径的第一种酶 RgpG 的缺乏会导致细胞分裂和形态的重大缺陷，并减少变形链球菌的生物膜形成，表明 RGP 在变形链球菌的细胞分裂和生物膜形成中发挥重要作用。这些结果不仅在变形链球菌中是新颖的，而且在产生 RGP 的其他链球菌中也是新颖的。这项研究还表明，变形链球菌中的 LytR-CpsA-Psr 家族蛋白 BrpA 和 Psr 参与 RGP 和可能的其他细胞壁糖聚合物与肽聚糖的附着。此外，结果还表明BrpA和Psr可能在变形链球菌的细胞分裂和生物膜形成中发挥直接作用。这项研究揭示了开发防龋疗法的新潜在目标。
Streptococcus mutans is known to possess rhamnose-glucose polysaccharide (RGP), a major cell wall antigen. S. mutans strains deficient in rgpG, encoding the first enzyme of the RGP biosynthesis pathway, were constructed by allelic exchange. The rgpG deficiency had no effect on growth rate but caused major defects in cell division and altered cell morphology. Unlike the coccoid wild type, the rgpG mutant existed primarily in chains of swollen, "squarish" dividing cells. Deficiency of rgpG also causes significant reduction in biofilm formation (P < 0.01). Double and triple mutants with deficiency in brpA and/or psr, genes coding for the LytR-CpsA-Psr family proteins BrpA and Psr, which were previously shown to play important roles in cell envelope biogenesis, were constructed using the rgpG mutant. There were no major differences in growth rates between the wild-type strain and the rgpG brpA and rgpG psr double mutants, but the growth rate of the rgpG brpA psr triple mutant was reduced drastically (P < 0.001). Under transmission electron microscopy, both double mutants resembled the rgpG mutant, while the triple mutant existed as giant cells with multiple asymmetric septa. When analyzed by immunoblotting, the rgpG mutant displayed major reductions in cell wall antigens compared to the wild type, while little or no signal was detected with the double and triple mutants and the brpA and psr single mutants. These results suggest that RgpG in S. mutans plays a critical role in cell division and biofilm formation and that BrpA and Psr may be responsible for attachment of cell wall antigens to the cell envelope.IMPORTANCE Streptococcus mutans, a major etiological agent of human dental caries, produces rhamnose-glucose polysaccharide (RGP) as the major cell wall antigen. This study provides direct evidence that deficiency of RgpG, the first enzyme of the RGP biosynthesis pathway, caused major defects in cell division and morphology and reduced biofilm formation by S. mutans, indicative of a significant role of RGP in cell division and biofilm formation in S. mutans. These results are novel not only in S. mutans, but also other streptococci that produce RGP. This study also shows that the LytR-CpsA-Psr family proteins BrpA and Psr in S. mutans are involved in attachment of RGP and probably other cell wall glycopolymers to the peptidoglycan. In addition, the results also suggest that BrpA and Psr may play a direct role in cell division and biofilm formation in S. mutans. This study reveals new potential targets to develop anticaries therapeutics.