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Structural variation in the O‐specific polysaccharides of Klebsiella pneumoniae serotype O1 and O8 lipopolysaccharide: evidence for clonal diversity in rfb genes
Author(s) -
Kelly Robert F.,
Severn Wayne B.,
Richards James C.,
Perry Malcolm B.,
MacLean Leann L.,
Tomás Juan M.,
Merino Susana,
Whitfield Chris
Publication year - 1993
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1993.tb00933.x
Subject(s) - galactan , biology , polysaccharide , serotype , disaccharide , gene cluster , klebsiella pneumoniae , microbiology and biotechnology , streptococcus pneumoniae , biochemistry , stereochemistry , gene , chemistry , escherichia coli , antibiotics
Summary 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 OAc 1 2/6 →3)‐β‐ d ‐Gal f ‐(1 →3)‐α‐ d ‐Gal p ‐(1→ d ‐Galactan I‐OAc →3)‐α‐ d ‐Gal p ‐(1 →3)‐β‐ d ‐Gal p ‐(1→ d ‐Galactan II. K. pneumoniae O8 mutant RFK‐1 was isolated by resistance to phage KO1‐2; strain RFK‐1 expressed only d ‐galactan I‐OAc. The 1 H‐ and 13 C‐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 β‐ d ‐galactofuranose residues; 60% of the available β‐ 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. rfb Kpo1 ‐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 rfb KpO1 probes under conditions of high stringency. Three serotype O2 strains produce d ‐galactan I and these strains also contained DNA sequences recognized by rfb KpO1 probes under high stringency. The physical maps of these homologous rfb chromosomal regions showed some polymorphism. Surprisingly, the rfb KpO8 region from K. pneumoniae serotype O8 was only recognized by rfb KpO1 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.