Abstract We report here the isolation of a Renibacterium salmoninarum DNA sequence capable of transforming a non-invasive Escherichia coli strain into a microorganism able to enter the fish cell line, CHSE-214. Immunofluorescence and electron microscopy techniques were used to assess the acquired invasive phenotype by HB101 E. coli cells, upon transformation with pPMV-189. This plasmid carries a 2282-bp R. salmoninarum DNA segment. The invasive phenotype is qonserved upon deletion of approximately 1000 bp at the 3′ end of the insert. The remaining segment contains an ORF region encoding a putative protein of about 30 kDa.