Study on the Iron-Acquisition Mechanism of Periodontal Bacteria

铁是一种必需的细菌营养物质，在体内细菌并不能自由获取，因为铁与宿主铁结合蛋白（如转铁蛋白、乳铁蛋白和血红蛋白）结合。然而，致病菌发展出特定的铁摄取系统，包括产生特定的细胞铁结合蛋白以在体内获取铁。对于牙周细菌，我们对它们的铁摄取系统知之甚少。在这项研究中，我们测定了牙周细菌，放线菌和牙龈卟啉单胞菌的铁摄取基因。得到了以下结果：1) a.l actinomycetemcomitans：这两个铁蛋白基因位于a.l actinomycetemcomitans Y4的调控基因actX的上游。铁蛋白是一种细菌铁结合蛋白，在细菌细胞中起铁的获取和储存作用。克隆了a.l actinomycetemcomitans Y4的铁蛋白基因，并对其进行了DNA序列分析。它们由486 bp（161个氨基酸）和498 bp（165个氨基酸）的开放阅读框组成。它们分别与流感嗜血杆菌铁蛋白基因具有80%和85%的同源性。Western blotting分析显示，与抗大肠杆菌铁蛋白兔血清反应的两个细胞蛋白（约20kDa）在a.c ortinomycetemcomitans Y4细胞中均有表达。2)牙床：牙床；牙龈的生长需要血红素。采用聚合酶链反应法测定了推测的牙龈假单胞菌血红蛋白结合蛋白基因。以脆弱拟杆菌血红素摄取蛋白基因（hupA）为引物设计PCR的寡核苷酸引物。从牙龈假单胞菌FDC 381基因组DNA中扩增出约1.3 kb的DNA片段，并对DNA序列进行分析。扩增DNA片段的部分序列与假单胞菌血凝素基因和蛋白酶基因具有高度的同源性。这些结果表明，牙龈假单胞菌可能通过这些基因产物捕获红细胞并将其分解为血红素。少

Iron, an essential bacterial nutrient, is not freely available for bacteria in vivo because iron is complexed with host iron-binding proteins such as transferrin, lactoferrin and hemoglobin. However, pathogenic bacteria develop specific iron-uptake systems including the production of specific cellular iron binding proteins to acquire iron in vivo. For periodontal bacteria, little is known about their iron-uptake system. In this study, we determined the genes for iron uptake in periodontal bacteria, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis. The following results were obtained.1) A.actinomycetemcomitans :The two ferritin genes were found in the upstream of a regulatory gene, actX of A.actinomycetemcomitans Y4. Ferritin is a bacterial iron binding protein, which acts iron acquisition and storage in bacterial cells. The ferritin genes in A.actinomycetemcomitans Y4 were cloned and their DNA sequence analyses were performed. They are consisted of 486 bp (161 amino ac … More ids) and 498 bp(165amino acids) open reading frames. They exhibited 80 % and 85 % homology with Haemophilus influenzae ferritin genes. The Western blotting analysis showed the two cellular proteins(approximately 20kDa), reacted with anti-Escherichia coli ferritin rabbit serum were expressed in A.actinomycetemcomitans Y4 cells.2) P.gingivalis :P.gingivalis requires hemin for its growth. The putative hemin biding protein genes were determined for P.gingi va/is by polymerase chain reaction method. The oligonucleotide primers for the PCR were designed from the Bacteroides fragilis hemin-uptake protein gene(hupA). Approximate 1.3-kb DNA fragments were amplified from P.gingivahs FDC 381 genomic DNA and the DNA sequences were analyzed. The partial DNA sequences of the amplified DNA fragments showed high homologies with the P.gingi valis hemagglutinin gene and protease genes. These results indicate that P.gingivalis might capture to erythrocytes and decompose them to acquire hemin by these gene products. Less