The complete DNA sequence of the O antigen gene region of Plesiomonas shigelloides serotype O17 which is identical to Shigella sonnei form I antigen

We cloned and determined the sequence of a DNA region of approximately 15-k b containing the cluster of genes required for O17 antigen expression in th e Escherichia coli K-12 strain from the chromosome of Plesiomonas shigelloi des serotype O17:H2 strain. The sequencing analysis revealed that the minim um essential region of the P. shigelloides O17 antigen gene cluster had a s ize of approximately 11.5-kb and contained 9 contiguous open reading frames (ORFs), which were almost identical to the corresponding ORFs of Shigella sonnei form I antigen gene region, except for 1S630 sequence, at the DNA as well as amino acid levels. The putative function of most of the ORFs could be determined on the basis of amino acid sequence similarities and charact eristics. In addition, the G + C content of the P. shigelloides O17 antigen genes was lower than that of the chromosomal DNA of P. shigelloides and S. sonnei, suggesting that both P. shigelloides O17 and S. sonnei form I anti gen genes had been derived from the same origin with a low G + C content.