Development of molecular genetics in oral bacteroides

(1)牙龈卟啉单胞菌(类杆菌)自杀表达载体pKDCMZ的构建以pKDCMZ为载体，用突变的超氧化物歧化酶(SOD)基因置换构建了一株超氧化物歧化酶(SOD)缺陷突变株。(2)利用Tn4351转座子诱变技术筛选无色突变株。从其中一个无色突变体中克隆了一个被Tn4351破坏的基因，并进行了部分测序。该基因推测产物(Porr)的氨基酸序列与脂肪嗜热芽孢杆菌、红霉菌erc1和链霉菌dnrJ编码的蛋白质的氨基酸序列有较高的相似性，这些蛋白质位于细胞膜上，在信号转导中起传感器的作用。

(1)Construction of a suicide plasmid (pKDCMZ) for Porphyromonas (Bacteroides) gingivalis.A suicide plasmid was constructed from a shuttle plasmid vector between E.coli and Bacteroides (pVAL-1). By use of pKDCMZ plasmid, a superoxide dismutase (SOD) -deficient mutant strain was constructed via gene replacement by a mutated sod. The SOD mutant strain showed a rapid viability loss on exposure to air, indicating that SOD is essential for aerotolerance of this organism.(2)Isolation of colorless mutant strains of P.gingivalis by use of Tn4351 transposon mutagenesis.Colorless mutant strains of P.gingivalis were isolated by trasconjugation between E.coli harboring R751 : : Tn4351OMEGA4 and P.gingivalis. A gene disrupted by Tn4351 was cloned from one of the colorless mutants and partially sequenced. The amino acid sequence of putative product of the gene (porR) has relatively high similarity with the amino acid sequences of proteins coded by Bacillus stearothermophilus degt, Saccharopolyspora erythraea eryC1, and Streptomyces peucetius dnrJ.These proteins are located at cytoplasmic membrane, functioning as a sensor in signal transduction.