ADAPTIVE ACID TOLERANCE OF STREPTOCOCCUS SOBRINUS

描述（由申请方提供）：两种变形链球菌，变形链球菌和远缘链球菌，被认为是人类龋齿的主要病原体。虽然这两个物种都是高度致龋的，但大多数研究都是用S。主要是因为S. mutans的强烈关联。在发达国家中，变异链球菌与龋齿的关系，但也因为相对容易对变异链球菌进行遗传操作。变形链球菌与S. sobrinus。众所周知，S.变形杆菌固有地比许多其它口腔细菌更耐酸，并且能够产生适应性耐酸性反应（ATR）（Belli和Marquis，1991;汉密尔顿和巴克利，1991）。此前，S。sobrinus，虽然本质上是耐酸性的，但被认为缺乏安装ATR的能力（Svensater等人，1997年）。最近，我们的实验室对S. sobrinus到环境酸化（Nascimento等人，2004年）。结果表明，S. sobrinus实际上能够在酸性pH下培养期间发展有力的ATR。有趣的是，我们的数据表明，S. sobrinus和S.变异人在更有趣的发现中，S. sobrinus在酸性条件下的生长并没有增强，因为它在许多其他生物体中，葡萄糖特异性磷酸烯醇丙酮酸糖：磷酸转移酶系统（PTS）的表达，在S.变形链球菌在低pH条件下生长受到抑制，在S.与pH7.0生长的细胞相比，pH5.0生长的sobrinus细胞（Nascimento等，2004年）。本申请的目的是扩展我们对S. sobrinus ATR的研究进展如下：（i）S. sobrinus的耐酸性分析。缺乏PTS的葡萄糖特异性酶II（EIIGIc）的sobrinus菌株。

DESCRIPTION (provided by applicant): Two species of mutans streptococci, Streptococcus mutans and Streptococcus sobrinus, are considered the primary etiological agents of human dental caries. Although both species are highly cariogenic, the majority of studies have been carried out with S. mutans; primarily because of the strong association of S. mutans with caries in developed nations, but also because of the relative ease of genetic manipulation of S. mutans compared to S. sobrinus. It is well known that S. mutans is inherently more acid resistant than many other oral bacteria and is able to mount an adaptive acid tolerance response (ATR) (Belli and Marquis, 1991; Hamilton and Buckley, 1991). Previously, S. sobrinus, although intrinsically acid tolerant, was considered to lack the capacity to mount an ATR (Svensater et al., 1997). Recently, our laboratory conducted a more detailed analysis of the responses of S. sobrinus to environmental acidification (Nascimento et al., 2004). Our results indicated that S. sobrinus was in fact capable of developing a vigorous ATR during cultivation at acidic pH. Interestingly, our data indicated that there are critical differences in the molecular mechanisms of acid adaptation by S. sobrinus and S. mutans. Among the more intriguing findings, expression of the F-ATPase of S. sobrinus was not enhanced by growth in acidic conditions, as it is in many other organisms, and expression of the glucose-specific phosphoenolpyruvate sugar: phosphotransferase system (PTS), which in S. mutans is repressed during growth at low pH, was two-fold higher in S. sobrinus cells grown at pH 5.0 compared to pH 7.0-grown cells (Nascimento et al., 2004). The goal of this application is to extend our investigations on the S. sobrinus ATR by pursuing the following specific aims: (i) Identification and characterization of acid tolerance responses of S. sobrinus, and (ii) analysis of the acid tolerance properties of a S. sobrinus strain lacking the glucose-specific enzyme II (EIIGIc) of the PTS.