Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin 300457, PR China.
TEDA School of Biological Sciences and Biotechnology, Nankai University, 23 Hongda Street, TEDA, Tianjin 300457, PR China.
Microbiology (Reading). 2010 Jun;156(Pt 6):1642-1649. doi: 10.1099/mic.0.037325-0. Epub 2010 Feb 25.
O-antigen is a component of the outer membrane of Gram-negative bacteria and is one of the most variable cell surface constituents, leading to major antigenic variability. The O-antigen forms the basis for bacterial serotyping. In this study, the O-antigen structure of Salmonella O66 was established, which differs from the known O-antigen structure of Escherichia coli O166 only in one linkage (most likely the linkage between the O-units) and O-acetylation. The O-antigen gene clusters of Salmonella O66 and E. coli O166 were found to have similar organizations, the only exception being that in Salmonella O66, the wzy gene is replaced by a non-coding region. The function of the wzy gene in E. coli O166 was confirmed by the construction and analysis of deletion and trans-complementation mutants. It is proposed that a functional wzy gene located outside the O-antigen gene cluster is involved in Salmonella O66 O-antigen biosynthesis, as has been reported previously in Salmonella serogroups A, B and D1. The sequence identity for the corresponding genes between the O-antigen gene clusters of Salmonella O66 and E. coli O166 ranges from 64 to 70 %, indicating that they may originate from a common ancestor. It is likely that after the species divergence, Salmonella O66 got its specific O-antigen form by inactivation of the wzy gene located in the O-antigen gene cluster and acquisition of two new genes (a wzy gene and a prophage gene for O-acetyl modification) both residing outside the O-antigen gene cluster.
O-抗原是革兰氏阴性细菌外膜的组成部分之一，是最具变异性的细胞表面成分之一，导致主要的抗原变异性。O-抗原是细菌血清型分型的基础。在这项研究中，确定了沙门氏菌 O66 的 O-抗原结构，与已知的大肠杆菌 O166 的 O-抗原结构仅在一个键（很可能是 O-单元之间的键）和 O-乙酰化方面存在差异。发现沙门氏菌 O66 和大肠杆菌 O166 的 O-抗原基因簇具有相似的组织，唯一的例外是沙门氏菌 O66 中的 wzy 基因被非编码区取代。通过构建和分析缺失和转互补突变体，证实了大肠杆菌 O166 中 wzy 基因的功能。据报道，一种位于 O-抗原基因簇外的具有功能的 wzy 基因参与了沙门氏菌 O66 O-抗原生物合成，这在沙门氏菌血清群 A、B 和 D1 中已有报道。沙门氏菌 O66 和大肠杆菌 O166 的 O-抗原基因簇之间相应基因的序列同一性为 64%至 70%，表明它们可能来自共同的祖先。很可能在物种分化后，沙门氏菌 O66 通过失活位于 O-抗原基因簇中的 wzy 基因并获得两个新基因（一个 wzy 基因和一个用于 O-乙酰化修饰的噬菌体基因）来获得其特定的 O-抗原形式，这两个基因都位于 O-抗原基因簇之外。
