Biochemical characterization and evaluation of virulence of a fructosyltransferase-deficient mutant of Streptococcus mutans V403
Biochemical characterization and evaluation of virulence of a fructosyltransferase-deficient mutant of Streptococcus mutans V403
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DOI：
10.1128/iai.57.11.3560-3569.1989
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发表时间：
1989-11
影响因子：
3.1
通讯作者：
V. Schröder;S. Michalek;F. Macrina
中科院分区：
文献类型：
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作者：
V. Schröder;S. Michalek;F. Macrina
变形链球菌细胞外果糖基转移酶（FTF）可能通过合成作为细胞外储存多糖的果聚糖聚合物，在龋齿的形成中发挥作用。我们试图在大鼠动物模型系统中确定 FTF 缺陷型变形链球菌菌株的毒性是否低于野生型细胞。来自变形链球菌GS5的克隆ftf基因序列用于通过将编码红霉素抗性的DNA片段插入ftf编码区来产生ftf基因的有缺陷的拷贝。通过使用遗传转化将携带有缺陷的ftf构建体的质粒引入变形链球菌V403中。这种有缺陷的构建体通过等位基因交换取代了 V403 染色体上携带的 ftf 基因的野生型副本。 FTF 活性测定表明重组菌株 V1741 缺乏果聚糖合成。然而，与 V403 制剂相比，该菌株的胞外蛋白制剂显示出生成葡萄糖聚合物（葡聚糖）的能力增强。 V1741 菌株对玻璃和大鼠牙齿表面的粘附水平与 V403 菌株相似。两种菌株都会导致大鼠牙齿表面中度腐烂；然而，与野生型菌株相比，FTF 缺陷菌株的致病性较低。这些结果表明，FTF 活性可能通过产生作为储存化合物的细胞外果聚糖来促进变形链球菌 V403 的致病性。
The Streptococcus mutans extracellular fructosyltransferase (FTF) enzyme may play a role in the formation of dental caries by synthesizing a fructan polymer that serves as an extracellular storage polysaccharide. We sought to determine if an FTF-deficient strain of S. mutans was less virulent than wild-type cells in a rat animal model system. Cloned ftf gene sequences from S. mutans GS5 were used to generate a defective copy of the ftf gene by inserting into the ftf coding region a DNA fragment which encoded erythromycin resistance. The plasmid which carried the defective ftf construct was introduced into S. mutans V403 by using genetic transformation. This defective construct replaced, by allelic exchange, the wild-type copy of the ftf gene carried on the V403 chromosome. FTF activity assays indicated that the recombinant strain, V1741, was deficient in fructan synthesis. However, extracellular protein preparations from this strain displayed an increased ability to generate glucose polymers (glucans) compared with V403 preparations. Levels of adherence to glass and rat tooth surfaces by strain V1741 were similar to those of the V403 strain. Both strains caused moderate decay on rat tooth surfaces; however, the FTF-deficient strain was less pathogenic compared with the wild-type strain. These results suggest that FTF activity contributes to the pathogenicity of S. mutans V403, possibly by generating extracellular fructans which serve as storage compounds.