Cell density modulates acid adaptation in Streptococcus mutans:: Implications for survival in biofilms
Cell density modulates acid adaptation in Streptococcus mutans:: Implications for survival in biofilms
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DOI：
10.1128/jb.183.23.6875-6884.2001
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发表时间：
2001-12-01
影响因子：
3.2
通讯作者：
Cvitkovitch, DG
中科院分区：
文献类型：
--
作者：
Li, YH;Hanna, MN;Cvitkovitch, DG
变形链球菌通常定殖在牙齿生物膜上，并在摄入可发酵膳食碳水化合物期间经常暴露于持续的酸性pH循环中。变形链球菌在低pH值下生存的能力是龋齿发病机制中的重要毒力因素。尽管对该生物体的酸适应机制进行了一些研究，但很少有工作关注在高细胞密度生物膜中生长的变形链球菌的耐酸性。目前尚不清楚生物膜生长、模式或高细胞密度是否会影响变形链球菌的酸适应。本研究旨在检测变形链球菌生物膜细胞的耐酸反应（ATR），并确定细胞密度对诱导酸适应的影响。首先将变形链球菌 BM71 细胞培养在肉汤培养物中，以检查与生长期、细胞密度、碳饥饿和培养物滤液诱导相关的酸适应。细胞还在基于恒化器的生物膜发酵罐中生长以形成生物膜。在恒化器中通过过量葡萄糖代谢产生的酸建立生物膜细胞对低pH的适应，然后进行3小时的pH 3.5酸冲击。去除生物膜和浮游细胞以测定存活百分比。结果表明，S. mutans BM71表现出低pH诱导的对数期ATR和碳饥饿诱导的稳定期耐酸性。发现细胞密度可以调节变形链球菌对数期细胞的酸适应，因为处于较高细胞密度或来自致密生物膜的预适应细胞比处于较低细胞密度的细胞表现出显着更高的对杀伤pH的抵抗力。对数期 ATR 也可以通过从低 pH 培养物中收集的中和培养物滤液来诱导，这表明培养物滤液含有参与变形链球菌酸适应的细胞外诱导成分。加热或蛋白酶处理消除了培养物滤液的诱导。结果还表明，comC、-D 或 -E 基因（编码细胞密度依赖性诱导遗传能力所必需的群体感应系统）缺陷的突变体的对数期 ATR 降低。向 comC 突变体中添加合成能力刺激肽 (CSP) 可恢复 ATR。这项研究表明，细胞密度和生物膜生长模式调节变形链球菌的酸适应，表明该生物体酸适应的最佳发展涉及低 pH 诱导和细胞间通讯。
Streptococcus mutans normally colonizes dental biofilms and is regularly exposed to continual cycles of acidic pH during ingestion of fermentable dietary carbohydrates. The ability of S. mutans to survive at low pH is an important virulence factor in the pathogenesis of dental caries. Despite a few studies of the acid adaptation mechanism of this organism, little work has focused on the acid tolerance of S. mutans growing in high-cell-density biofilms. It is unknown whether biofilm growth, mode or high cell density affects acid adaptation by S. mutans. This study was initiated to examine the acid tolerance response (ATR) of S. mutans biofilm cells and to determine the effect of cell density on the induction of acid adaptation. S. mutans BM71 cells were first grown in broth cultures to examine acid adaptation associated with growth phase, cell density, carbon starvation, and induction by culture filtrates. The cells were also grown in a chemostat-based biofilm fermentor for biofilm formation. Adaptation of biofilm cells to low pH was established in the chemostat by the acid generated from excess glucose metabolism, followed by a pH 3.5 acid shock for 3 h. Both biofilm and planktonic cells were removed to assay percentages of survival. The results showed that S. mutans BM71 exhibited a log-phase ATR induced by low pH and a stationary-phase acid resistance induced by carbon starvation. Cell density was found to modulate acid adaptation in S. mutans log-phase cells, since pre-adapted cells at a higher cell density or from a dense biofilm displayed significantly higher resistance to the killing pH than the cells at it lower cell density. The log-phase ATR could also be induced by a neutralized culture filtrate collected from a low-pH culture, suggesting that the culture filtrate contained an extracellular induction component(s) involved in acid adaptation in S. mutans. Heat or proteinase treatment abolished the induction by the culture filtrate. The results also showed that mutants defective in the comC, -D, or -E genes, which encode a quorum sensing system essential for cell density-dependent induction of genetic competence, had a diminished log-phase ATR. Addition of synthetic competence stimulating peptide (CSP) to the comC mutant restored the ATR. This study demonstrated that cell density and biofilm growth mode modulated acid adaptation in S. mutans, suggesting that optimal development of acid adaptation in this organism involves both low pH induction and cell-cell communication.