Department of Microbiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan.
PLoS One. 2012;7(9):e43722. doi: 10.1371/journal.pone.0043722. Epub 2012 Sep 7.
The periodontal pathogen Porphyromonas gingivalis colonizes largely through FimA fimbriae, composed of polymerized FimA encoded by fimA. fimA exists as a single copy within the fim gene cluster (fim cluster), which consists of seven genes: fimX, pgmA and fimA-E. Using an expression vector, fimA alone was inserted into a mutant from which the whole fim cluster was deleted, and the resultant complement exhibited a fimbrial structure. Thus, the genes of the fim cluster other than fimA were not essential for the assembly of FimA fimbriae, although they were reported to influence FimA protein expression. It is known that there are various genotypes for fimA, and it was indicated that the genotype was related to the morphological features of FimA fimbriae, especially the length, and to the pathogenicity of the bacterium. We next complemented the fim cluster-deletion mutant with fimA genes cloned from P. gingivalis strains including genotypes I to V. All genotypes showed a long fimbrial structure, indicating that FimA itself had nothing to do with regulation of the fimbrial length. In FimA fimbriae purified from the complemented strains, types I, II, and III showed slightly higher thermostability than types IV and V. Antisera of mice immunized with each purified fimbria principally recognized the polymeric, structural conformation of the fimbriae, and showed low cross-reactivity among genotypes, indicating that FimA fimbriae of each genotype were antigenically different. Additionally, the activity of a macrophage cell line stimulated with the purified fimbriae was much lower than that induced by Escherichia coli lipopolysaccharide.
牙周病原菌牙龈卟啉单胞菌主要通过 FimA 菌毛定植，菌毛由 FimA 编码的聚合 FimA 组成。fimA 存在于 fim 基因簇（fim 簇）内的单个拷贝中，该基因簇由七个基因组成：fimX、pgmA 和 fimA-E。使用表达载体，将 fimA 单独插入到整个 fim 簇缺失的突变体中，所得的互补体显示出菌毛结构。因此，fim 簇中除 fimA 以外的基因对于 FimA 菌毛的组装不是必需的，尽管它们被报道会影响 FimA 蛋白的表达。已知 fimA 有多种基因型，并且表明基因型与 FimA 菌毛的形态特征有关，特别是长度，以及与细菌的致病性有关。我们接下来用从包括基因型 I 至 V 的牙龈卟啉单胞菌菌株克隆的 fimA 基因来补充 fim 簇缺失突变体。所有基因型均显示出长菌毛结构，表明 FimA 本身与菌毛长度的调节无关。在从互补菌株中纯化的 FimA 菌毛中，类型 I、II 和 III 比类型 IV 和 V 显示出稍微更高的热稳定性。用每种纯化菌毛免疫的小鼠抗血清主要识别菌毛的聚合、结构构象，并且在基因型之间显示出低的交叉反应性，表明每个基因型的 FimA 菌毛在抗原性上是不同的。此外，用纯化菌毛刺激的巨噬细胞系的活性远低于大肠杆菌脂多糖诱导的活性。
