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首页> 外文期刊>Infection and immunity >Characteristics and cariogenicity of a fructanase-defective Streptococcus mutants strain.
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Characteristics and cariogenicity of a fructanase-defective Streptococcus mutants strain.

机译：果糖酶缺陷型链球菌突变株的特征和致龋性。

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Polymers of D-fructose produced by a variety of oral bacteria are believed to function as extracellular carbohydrate reserves. Degradation of these polysaccharides in plaque following exhaustion of dietary carbohydrates is thought to contribute to the extent and duration of the acid challenge to the tooth surface and thus to the initiation and progression of dental caries. Streptococcus mutans produces a fructanase, the product of the fruA gene, which is capable of degrading beta(2,6)- and beta(2,1)-linked fructans that are commonly synthesized by dental plaque microorganisms. To evaluate the role of the FruA protein in exopolysaccharide metabolism and to assess the contribution of this enzyme to the pathogenic potential of S. mutans, a fructanase-deficient strain of S. mutans was constructed. Inactivation of a cloned fruA gene was accomplished in Escherichia coli by using a mini-Mu dE transposon, and then an isogenic mutant of S. mutans UA159 was constructed by allelic exchange. Successful inactivation of fruA was confirmed through the use of biochemical assays, Western blotting (immunoblotting) with anti-recombinant FruA antisera, and Southern hybridization. The data indicated that FruA was the only fructan hydrolase produced by S. mutans UA159. Inactivation of fruA had no significant effects on glucosyltransferase or fructosyltransferase activity. In the rat caries model using animals fed a high-sucrose diet and ad libitum, there were no significant differences in the number or severity of smooth surface, sulcal, or root caries elicited by the fruA mutant and the wild-type organism.
机译：据信由多种口腔细菌产生的D-果糖的聚合物起细胞外碳水化合物储备的作用。人们认为，饮食中碳水化合物耗尽后牙菌斑中这些多糖的降解有助于酸挑战牙齿表面的程度和持续时间，从而有助于龋齿的发生和发展。变形链球菌产生一种果聚糖酶，它是fruA基因的产物，它能够降解通常由牙菌斑微生物合成的与β（2,6）和β（2,1）连接的果聚糖。为了评估FruA蛋白在胞外多糖代谢中的作用并评估该酶对变形链球菌致病潜力的贡献，构建了一种果糖酶缺陷型变形链球菌。通过使用微型Mu dE转座子在大肠杆菌中完成了克隆的fruA基因的灭活，然后通过等位基因交换构建了变形链球菌UA159的同基因突变体。通过使用生化分析，具有抗重组FruA抗血清的Western印迹（免疫印迹）和Southern杂交，证实了fruA的成功灭活。数据表明，FruA是变形链球菌UA159产生的唯一果聚糖水解酶。 fruA的失活对葡萄糖基转移酶或果糖基转移酶活性没有明显影响。在使用动物食用高蔗糖饮食和随意食用的大鼠龋齿模型中，fruA突变体和野生型生物体引起的平滑表面，沟渠或根龋的数量或严重程度没有显着差异。

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