Identification of genes associated with copper tolerance in an adhesion-defective mutant of Aeromonas veronii biovar sobria

TnphoA mutagenesis was used to identify adhesins of Aeromonas veronii biova r sobria 3767, a strain isolated from a diarrhoeal stool specimen. Six muta nts, from a library of 154, exhibited significantly reduced levels of adhes ion to HEp-2 cells. Primers to the terminal regions of TnphoA were used for inverse PCR and the product from one mutant was cloned into pBluescript an d partial sequence data obtained. Scanning GenBank and EMBL data bases reve aled DNA sequence similarity to the copA gene of Pseudomonas syringae pv. t omato which confers resistance to copper and other heavy metals. The transp oson was located within the copA gene and the mutant exhibited a reduced to lerance to copper. Primer walking, using the inverse PCR product as a templ ate, revealed three open reading frames (ORFs) copA, B and C in A. veronii biovar sobria 3767. The predicted amino acid sequences of ORFs A and B had significant homology (55 and 34% respectively) to the copA and B proteins o f P. syringae. No amino acid or DNA sequence homology existed between ORF C of strain 3767 and any other gene in the data bases scanned. Further analy sis of the nucleotide sequence failed to reveal the presence of typical cop per regulatory genes within the vicinity of the Aeromonas sequence. The ass ociation between copper tolerance and adhesion in A. veronii biovar sobria requires further study. (C) 2000 Federation of European Microbiological Soc ieties. Published by Elsevier Science B.V. All rights reserved.