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 mutation in the 3-deoxy-D- mannooctulosonic acid (Kdo) 8-phosphate synthase gene ( kdsA) of Salmonella enterica sv Typhimurium AG701i50 was cloned from the reference strain of Pasteurella trehalosi (haemolytica) serotype T3. Subcloning and DNA sequence analysis identified an open reading frame (ORF) of 854 nucleotides which could encode a protein of 31.0 kDa. Protein expression of this ORF using a T7 polymerase system yielded a unique polypeptide of approximately 31 kDa, in excellent agreement with predicted size of the encoded protein. The deduced amino acid sequence 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 located adjacent to the leukotoxin gene cluster (IktCABD).