A GENE REGION IN DICHELOBACTER-NODOSUS ENCODING A LIPOPOLYSACCHARIDE EPITOPE

Dichelobacter nodosus is a Gram-negative anaerobic bacterium that is t he causative organism of footrot in sheep. A D. nodosus locus responsi ble for a modification of the host lipopolysaccharide (LPS) in Escheri chia coli was cloned and sequenced. Genetic studies showed that the mo dification occurred within the inner-core region of the host LPS, most likely to one or more of the heptose molecules. Antibodies eluted fro m the modified LPS reacted preferentially with the lipid-A-core region of D. nodosus LPS, suggesting that the cloned epitope was present in this region of the D. nodosus LPS, The gene responsible for the modifi cation, IpsA, potentially encoded a polypeptide of approximately 37 kD a which was highly basic, a characteristic of enzymes which interact w ith the acidic inner LPS core. The IpsA gene appeared to be arranged i n a complex operon with a downstream gene, prfC, which encoded a prote in with similarity to E. coli peptide-chain release factor 3.