Kelly R F, Severn W B, Richards J C, Perry M B, MacLean L L, Tomás J M, Merino S, Whitfield C
Department of Microbiology, University of Guelph, Ontario, Canada.
Mol Microbiol. 1993 Nov;10(3):615-25. doi: 10.1111/j.1365-2958.1993.tb00933.x.
The O-polysaccharide fraction of the lipopolysaccharide from Klebsiella pneumoniae serotype O8 was found to comprise two galactose-containing homopolymers. Structural analysis, using chemical and high-field nuclear magnetic resonance (NMR) techniques, established that the K. pneumoniae O8 polysaccharides are composed of the linear, disaccharide repeating units [formula: see text] K. pneumoniae O8 mutant RFK-1 was isolated by resistance to phage KO1-2; strain RFK-1 expressed only D-galactan I-OAc. The 1H- and 13C-NMR resonances from this O-polysaccharide indicate that all of the O-acetyl groups within the K. pneumoniae O8 polysaccharide are carried on D-galactan I and O-acetylation occurs only on the beta-D-galactofuranose residues; 60% of the available beta-D-galactofuranose residues are non-acetylated. The O-acetylation of the remaining residues is equally distributed between the O-2 and O-6 positions. The carbohydrate backbone structures in the O8 polysaccharide are identical to D-galactan I and II expressed by K. pneumoniae O1, accounting for the antigenic cross-reaction between strains belonging to serotypes O1 and O8. However, the O1 polysaccharides are not acetylated and the O-acetyl groups present in the K. pneumoniae serotype O8 polysaccharides provide a structural basis for their recognition as distinct serotypes. The rfb (O-polysaccharide biosynthesis) gene cluster of K. pneumoniae serotype O1 determines the synthesis of D-galactan I. rfbKpO1-specific gene probes were used to examine conservation in the rfb gene clusters of other K. pneumoniae serotypes which produce D-galactan I. Six O1 strains were examined and all showed hybridization with rfbKpO1 probes under conditions of high stringency. Three serotype O2 strains produce D-galactan I and these strains also contained DNA sequences recognized by rfbKpO1 probes under high stringency. The physical maps of these homologous rfb chromosomal regions showed some polymorphism. Surprisingly, the rfbKpO8 region from K. pneumoniae serotype O8 was only recognized by rfbKpO1 probes under low-stringency hybridization conditions, providing evidence for two substantially different clonal groups of rfb genes from K. pneumoniae strains with structurally related O-antigens.
肺炎克雷伯菌O8血清型脂多糖的O-多糖部分被发现由两种含半乳糖的均聚物组成。利用化学和高场核磁共振（NMR）技术进行的结构分析确定，肺炎克雷伯菌O8多糖由线性二糖重复单元组成[化学式：见原文]。通过对噬菌体KO1-2的抗性分离出肺炎克雷伯菌O8突变体RFK-1；菌株RFK-1仅表达D-半乳聚糖I-OAc。该O-多糖的1H和13C-NMR共振表明，肺炎克雷伯菌O8多糖中的所有O-乙酰基都位于D-半乳聚糖I上，且O-乙酰化仅发生在β-D-呋喃半乳糖残基上；60%的可用β-D-呋喃半乳糖残基未被乙酰化。其余残基的O-乙酰化在O-2和O-6位置上平均分布。O8多糖中的碳水化合物主链结构与肺炎克雷伯菌O1表达的D-半乳聚糖I和II相同，这解释了O1和O8血清型菌株之间的抗原交叉反应。然而，O1多糖未被乙酰化，肺炎克雷伯菌O8血清型多糖中存在的O-乙酰基为它们被识别为不同血清型提供了结构基础。肺炎克雷伯菌O1血清型的rfb（O-多糖生物合成）基因簇决定了D-半乳聚糖I的合成。rfbKpO1特异性基因探针用于检测其他产生D-半乳聚糖I的肺炎克雷伯菌血清型rfb基因簇中的保守性。检测了六个O1菌株，在高严谨度条件下，所有菌株均与rfbKpO1探针杂交。三个O2血清型菌株产生D-半乳聚糖I，在高严谨度条件下，这些菌株也含有被rfbKpO1探针识别的DNA序列。这些同源rfb染色体区域的物理图谱显示出一些多态性。令人惊讶的是，肺炎克雷伯菌O8血清型的rfbKpO8区域仅在低严谨度杂交条件下被rfbKpO1探针识别，这为来自具有结构相关O抗原的肺炎克雷伯菌菌株的rfb基因的两个基本不同的克隆群提供了证据。
