THE KDSA GENE OF PASTEURELLA-TREHALOSI (HAEMOLYTICA) SEROTYPE T3 IS FUNCTIONALLY AND GENETICALLY HOMOLOGOUS TO THAT OF ESCHERICHIA-COLI

A DNA fragment capable of complementing a temperature-sensitive mutati on in the 3-deoxy-D-mannooctulosonic acid (Kdo) 8-phosphate synthase g ene (kdsA) of Salmonella enterica sv Typhimurium AG701i50 was cloned f rom the reference strain of Pasteurella trehalosi (haemolytica) seroty pe T3. Subcloning and DNA sequence analysis identified an open reading frame (ORF) of 854 nucleotides which could encode a protein of 31.0 k Da. Protein expression of this ORF using a T7 polymerase system yielde d a unique polypeptide of approximately 31 kDa, in excellent agreement with predicted size of the encoded protein. The deduced amino acid se quence of this ORF has 88.8 and 94.3% homology with the KdsA proteins of Escherichia coli and Haemophilus influenzae, respectively. Southern blot analysis of chromosomal DNA showed that kdsA was present in all 16 serotypes of P. haemolytica/P. trehalosi. The position of the kdsA gene differed among the two species; only in P. trehalosi is kdsA loca ted adjacent to the leukotoxin gene cluster (IktABD).