Regulation Of Sugar Transport And Metabolism In Oral Bacteria

颊纤毛菌ATCC 14201是一种存在于牙齿表面的口腔生物膜中的革兰氏阴性厌氧杆状细菌。该生物体的测序基因组揭示了三个连续的基因位点：Lebu_1525，1526和1527。这些基因的翻译产物分别与磷酸-β-葡糖苷酶（Pagl）、调节蛋白（GntR）和磷酸烯醇化酶依赖的糖转运蛋白（EIICB）具有显著的同源性。在非口腔细菌物种中，这些基因包含促进蔗糖异构体代谢的sim操纵子。生长研究表明，L. buccalis发酵各种各样的碳水化合物，包括蔗糖的五种异构体中的四种。在异构双糖上的生长引发了与Lebu_1525编码的大小相当的50 kDa多肽的表达。后者的基因被克隆，并表达的蛋白质纯化到同质从大肠杆菌TOP 10细胞。在两个辅因子，NAD+和Mn 2+离子的存在下，该酶容易水解对硝基苯基-β-吡喃葡萄糖苷6-磷酸（PNP G6 P），蔗糖的磷酸化异构体的显色类似物。通过比较序列比对、免疫反应性和特征基序，该酶可以归属于糖基水解酶超家族的家族4的磷酸-β-葡糖苷酶（Pagl）进化枝。我们认为Lebu_1527和1525的产物催化L.颊肌。最近描述了四种遗传多样性，但16 S rDNA相关的Leptotrichia种：L.古德费洛维湖hofstadii，L. shahii和L.瓦代。这些新物种的表型特征，关于碳水化合物的利用，也已确定。我们的调查结果已提交，并接受，发表在杂志《分子口腔微生物学》。

Leptotrichia buccalis ATCC 14201 is a Gram-negative, anaerobic rod-shaped bacterium resident in oral biofilm at the tooth surface. The sequenced genome of this organism reveals three contiguous genes at loci: Lebu_1525,1526 and 1527. The translation products of these genes exhibit significant homology with phospho-α-glucosidase (Pagl), a regulatory protein (GntR) and a phosphoenol pyruvate-dependent sugar transport protein (EIICB), respectively. In non-oral bacterial species, these genes comprise the sim operon that facilitates sucrose isomer metabolism. Growth studies showed that L. buccalis fermented a wide variety of carbohydrates, including four of the five isomers of sucrose. Growth on the isomeric disaccharides elicited expression of a 50kDa polypeptide comparable in size to that encoded by Lebu_1525. The latter gene was cloned, and the expressed protein was purified to homogeneity from Escherichia coli TOP 10 cells. In the presence of two cofactors, NAD+ and Mn2+ ion, the enzyme readily hydrolyzed p-nitrophenyl-α-glucopyranoside 6-phosphate (pNPαG6P), a chromogenic analog of the phosphorylated isomers of sucrose. By comparative sequence alignment, immuno-reactivity and signature motifs, the enzyme can be assigned to the phospho-α-glucosidase (Pagl) clade of Family 4 of the glycosyl hydrolase super family. We suggest that the products of Lebu_1527 and 1525, catalyze the phosphorylative translocation and hydrolysis of sucrose isomers in L. buccalis, respectively. Four genetically diverse, but 16S rDNA related species of Leptotrichia have recently been described: L. goodfellowii, L. hofstadii, L. shahii and L. wadei. The phenotypic traits of these new species, with respect to carbohydrate utilization, have also been determined.The results of our investigation have been submitted, and accepted, for publication in the journal MOLECULAR ORAL MICROBIOLOGY.