A novel protein of Erysipelothrix rhusiopathiae that confers haemolytic activity on Escherichia coli

Erysipelothrix rhusiopathiae, the cause of swine erysipelas and human erysi peloid, produces a haemolysin. A recombinant plasmid, pHLY, conferring haem olytic activity on Escherichia coli was isolated from a genomic library of fry. rhusiopathiae strain Tama-96. This plasmid was stable in RecA(-) E. co li, but unstable in a RecA(+) strain. A spontaneous deletion plasmid, pMini -HLY, also conferring haemolytic activity was derived from pHLY. Two ORFs w ere detected in pHLY. Analysis of pMini-HLY and other deletion clones estab lished that ORF2 was associated with haemolytic activity. The sequence of O RF1 was highly homologous to those of transposases in the IS30 family. The deletion which generated pMini-HLY was between two short direct repeat (DR) sequences flanking the ORF1 sequence, and there were inverted repeat seque nces inside the two DR sequences, suggesting an insertion element. No seque nce homology to the deduced amino acid sequence of ORF2 was detected in the databases, but its sequence was characteristic of a surface lipoprotein. W estern blot analysis, using antiserum against the 16 kDa protein produced f rom ORF2, found the protein to be commonly distributed in all Erysipelothri x species.