T. Sugiyama et al., GENETIC-ANALYSIS OF ESCHERICHIA-COLI O9 RFB - IDENTIFICATION AND DNA-SEQUENCE OF PHOSPHOMANNOMUTASE AND GDP-MANNOSE PYROPHOSPHORYLASE GENES, Microbiology, 140, 1994, pp. 59-71
Subcloning, transposon insertion, and deletion analysis revealed that
the Escherichia coli O9 rfb region is about 12 kb in size. The region
encodes at least: seven polypeptides of 89, 74, 55, 50, 44, 41 and 39.
5 kDa. Southern of hybridization analysis of rfb regions of E. coli O8
and O9, and Klebsiella O3 and O5 serotypes (all of these O polysaccha
rides are mannose homopolymers and the structures of the repeating uni
t of E. coli O9 and Klebsiella O3 are identical) showed that a central
region specific for E. coli O9 and Klebsiella O3 is flanked by two re
gions common to all four. Complementation experiments using strains wi
th known defects and specific tests for the enzymic activity showed th
at the 50 and 55 kDa polypeptides, encoded by the common region, are p
hosphomannomutase (PMM) and GDP-mannose pyrophosphorylase (GMP), respe
ctively. Nucleotide sequencing of the region revealed the presence of
two genes, rfbK and rfbM, analogous to the corresponding genes of Salm
onella typhimurium. In E. coli O9, rfbK and rfbM encode proteins of 46
0 amino acids (50 809 Da) and 471 amino acids (52 789 Da). The amino a
cid sequence of GMP was conserved in RfbMs of E. coli O7 and Salmonell
a groups B, C1 and C2, CpsB of S. typhimurium, AlgA of Pseudomonas aer
uginosa, and XanB of Xanthomonas campestris. The phylogenetic trees of
PMM and GMP were different in topology and in the evolutionary distan
ces from ancestors.