Elucidation of Mechanisms in Fimbrial Morphogenesis in Periodontopathogens

1.牙周病病原菌牙龈卟啉单胞菌菌膜。牙龈似乎携带三种不同类型的菌毛，分别由40-kDa的FimA蛋白、75-kDa的Mfa蛋白和53-kDa蛋白作为主要亚基组成。这三种菌毛在牙龈链球菌菌株W83中的分布似乎不携带任何一种。虽然它有fimA（基因型IV）基因，但似乎不表达fimA菌膜。由于mfa基因在染色体中被破坏，它不会产生mfa菌膜。在菌株ATCC 33277中产生了FimA和Mfa两种菌毛。包括381在内的一些牙龈假单胞菌菌株似乎具有这三种菌毛。fimA基因的变异目前报道的fimA基因有6种基因型。我们已经从基因型I、Ib和II菌株中纯化了菌毛。它们有大量用于净化的菌毛。然而，我们不知道是否所有的基因型菌株都在细胞表面携带大量的毛膜。不同fimA基因型菌株菌毛的不同提取方法基因型I型菌毛可以用温和的缓冲液对细菌细胞进行简单的洗涤而有选择性地提取。然而，其他基因型的Ib和II不能通过这种洗涤提取。它们可以通过法式压滤机使细胞破裂而溶解。这些结果可能意味着它们的纤维长度非常不同。基因I型的毛很长，而其他基因型的毛太短而不能从细胞表面剪下来的假设可以被证实。fimXY基因似乎在fimA蛋白的表达中起着重要的作用。fimR基因的产物，一个正调节因子，被发现与fimXY上游的区域结合以产生毛蛋白。

1.Fimbriae in Porphyromonas gingivalis, a periodontopathogenP.gingivalis seems to carry three different types of fimbriae which are composed of 40-kDa FimA,75-kDa Mfa, and 53-kDa protein, respectively, as a major subunit.2.Distribution of the three fimbriae in P.gingivalisStrain W83 seems to carry none of them. Although it has the fimA (genotype IV) gene, it does not seem to express FimA fimbriae. Because the mfa gene is disrupted in the chromosome, it does not produce Mfa fimbriae. Two fimbriae, FimA and Mfa, are produced in strain ATCC 33277. Some of the P.gingivalis strains including 381 appear to have the three fimbriae.3.Variation of fimA fimbriaeThere are six genotypes in the fimA gene, thus far reported. We have purified fimbriae from genotype I,Ib, and II strains. They have a plenty of fimbriae for purification. However, we do not know whether all the genotype strains carry a plenty of fimbraie on the cell surface.4.Different extraction methods for fimbriae from strains with different fimA genotypesGenotype I fimbraie can be selectively extracted by a simple washing of bacterial cells with a mild buffer. However, other genotype fimbraie of Ib and II could not be extracted by such washing. They can be solubilized through the cell breakage by a French Press. These results might imply that they have fibers with very different lengths. This assumption that genotype I fimbriae are long, but other genotypes of fimbraie are too short to be sheared off from the cell surfaces could be verified.5.Regulation in fimbrial morphogenesisThe genes of fimXY appear to play an important role in expression of fimA protein in fimbrial morphogenesis. The product of the fimR gene, a positive regulator, is discovered to bind to the region upstream from fimXY for production of the fimbrial protein.