Isolation and characterization of transposon-derived fimbria-deficient mutants of Porphyromonas gingivalis

转座子衍生的，菌毛缺陷的牙龈卟啉单胞菌突变体已被分离和鉴定，以确定一个新的染色体位点所必需的菌毛。fimA基因编码菌毛的主要亚基蛋白fimbrilin，位于最大的NotI片段（780 kb）上。至少有8个独立的，菌毛缺陷的突变体被发现有插入300 kb的NotI片段。通过基因组Southern分析判断，几乎所有的突变体都在有限的区域内插入。因此，我们从大肠杆菌7个突变体之一的AG 30 -4中克隆了含有Tn 4351的染色体片段。对邻近Tn 4351的克隆的牙龈卟啉单胞菌DNA片段进行测序。获得的核苷酸序列显示，一个双组分的信号转导系统被转座子插入中断，两个基因，fimS，一个传感器组氨酸激酶基因和fimR，一个响应调节基因被发现作为一个串联排列在这个区域。在7个突变体中，6个突变体在fimS上有插入，只有1个突变体在fimR上有插入。这种双组分系统是在这种生物体中发现的第一个系统，并参与菌毛形成。

Transposon-derived, fimbria-deficient mutants of Porphyromonas gingivalis have been isolated and characterized to identify a new chromosomal locus essential for fimbriation. The fimA gene coding for fimbrilin, a major subunit protein of fimbriae, was located on the largest NotI fragment (780kb). At least 8 independent, fimbria-deficient mutants were found to have insertions on a 300kb NotI fragment. Almost all the mutants had insertions in a limited area, judged by genomic Southern analysis. Therefore we cloned the Tn4351 containing fragment of the chromosome from AG30-4, one of the 7 mutants in Escherichia coli. A cloned P. gingivalis DNA fragment adjacent to Tn4351 was sequenced. The nucleotide sequence obtained revealed that a two component signal transduction system was interrupted by the transposon insertion, and two genes, fimS, a sensor histidine kinase gene and fimR, a response regulator gene were found as a tandem arrangement in this region. Among the 7 mutants 6 mutants had insertions in fimS and only one in fimR. This two-component system is the first one found in this organism and is involved in fimbriation.