Kachlany S C, Planet P J, Bhattacharjee M K, Kollia E, DeSalle R, Fine D H, Figurski D H
Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
J Bacteriol. 2000 Nov;182(21):6169-76. doi: 10.1128/JB.182.21.6169-6176.2000.
The gram-negative coccobacillus, Actinobacillus actinomycetemcomitans, is the putative agent for localized juvenile periodontitis, a particularly destructive form of periodontal disease in adolescents. This bacterium has also been isolated from a variety of other infections, notably endocarditis. Fresh clinical isolates of A. actinomycetemcomitans form tenacious biofilms, a property likely to be critical for colonization of teeth and other surfaces. Here we report the identification of a locus of seven genes required for nonspecific adherence of A. actinomycetemcomitans to surfaces. The recently developed transposon IS903phikan was used to isolate mutants of the rough clinical isolate CU1000 that are defective in tight adherence to surfaces (Tad(-)). Unlike wild-type cells, Tad(-) mutant cells adhere poorly to surfaces, fail to form large autoaggregates, and lack long, bundled fibrils. Nucleotide sequencing and genetic complementation analysis revealed a 6.7-kb region of the genome with seven adjacent genes (tadABCDEFG) required for tight adherence. The predicted TadA polypeptide is similar to VirB11, an ATPase involved in macromolecular transport. The predicted amino acid sequences of the other Tad polypeptides indicate membrane localization but no obvious functions. We suggest that the tad genes are involved in secretion of factors required for tight adherence of A. actinomycetemcomitans. Remarkably, complete and highly conserved tad gene clusters are present in the genomes of the bubonic plague bacillus Yersinia pestis and the human and animal pathogen Pasteurella multocida. Partial tad loci also occur in strikingly diverse Bacteria and Archaea. Our results show that the tad genes are required for tight adherence of A. actinomycetemcomitans to surfaces and are therefore likely to be essential for colonization and pathogenesis. The occurrence of similar genes in a wide array of microorganisms indicates that they have important functions. We propose that tad-like genes have a significant role in microbial colonization.
革兰氏阴性球杆菌——伴放线放线杆菌，被认为是局限性青少年牙周炎的病原体，这是一种在青少年中具有特别破坏性的牙周疾病形式。这种细菌也已从多种其他感染中分离出来，尤其是心内膜炎。伴放线放线杆菌的新鲜临床分离株会形成坚韧的生物膜，这一特性可能对其在牙齿和其他表面的定殖至关重要。在此，我们报告了对伴放线放线杆菌非特异性黏附于表面所需的一个由七个基因组成的基因座的鉴定。最近开发的转座子IS903phikan被用于分离粗糙临床分离株CU1000的突变体，这些突变体在紧密黏附于表面方面存在缺陷（Tad(-)）。与野生型细胞不同，Tad(-)突变体细胞对表面的黏附性很差，无法形成大的自聚集体，并且缺乏长的、成束的纤丝。核苷酸测序和基因互补分析揭示了基因组中一个6.7 kb的区域，其中有七个相邻基因（tadABCDEFG）是紧密黏附所必需的。预测的TadA多肽与VirB11相似，VirB11是一种参与大分子运输的ATP酶。其他Tad多肽的预测氨基酸序列表明它们定位于膜上，但没有明显功能。我们认为tad基因参与了伴放线放线杆菌紧密黏附所需因子的分泌。值得注意的是，在鼠疫杆菌耶尔森氏菌和人畜共患病原体多杀巴斯德氏菌的基因组中存在完整且高度保守的tad基因簇。部分tad基因座也存在于种类惊人的细菌和古细菌中。我们的结果表明，tad基因是伴放线放线杆菌紧密黏附于表面所必需的，因此可能对定殖和发病机制至关重要。在多种微生物中出现相似基因表明它们具有重要功能。我们提出，类tad基因在微生物定殖中具有重要作用。
