DNA Adenine Methylase Is Essential for Viability and Plays a Role in the Pathogenesis of Yersinia pseudotuberculosis and Vibrio cholerae

Abstract

Salmonella strains that lack or overproduce DNA adenine methylase (Dam) elicit a protective immune response to different Salmonella species. To generate vaccines against other bacterial pathogens, the dam genes of Yersinia pseudotuberculosis and Vibrio cholerae were disrupted but found to be essential for viability. Overproduction of Dam significantly attenuated the virulence of these two pathogens, leading to, in Yersinia, the ectopic secretion of virulence proteins (Yersinia outer proteins) and a fully protective immune response in vaccinated hosts. Dysregulation of Dam activity may provide a means for the development of vaccines against varied bacterial pathogens

Alteration of DNA adenine methylase (Dam) activity in Pasteurella multocida causes increased spontaneous mutation frequency and attenuation in mice

“…The attenuation of strains with altered dam expression is apparently due to 'inappropriate' expression of virulence factors that results from the failure of Dam to regulate their transcription (Heithoff et al, 1999). In Salmonella, a similar attenuating effect occurs in dam deletion mutants (Heithoff et al, 1999); mutation of the dam gene is lethal in Y. pseudotuberculosis and V. cholerae (Julio et al, 2001).…”

“…Dam-overproducing strains of S. enterica, Y. pseudotuberculosis and V. cholerae are all attenuated (Heithoff et al, 1999;Julio et al, 2001). Similarly, our Dam-overproducing P. multocida strain was attenuated using a mouse model.…”

“…Interestingly, the inappropriate expression of virulence factors in Dam-altered S. enterica, Y. pseudotuberculosis and V. cholerae not only causes attenuation, but it also renders them highly effective as live attenuated vaccines (Heithoff et al, 1999Julio et al, 2001). Although P. multocida antigens have been identified that have potential as vaccines (Adler et al, 1999;Confer et al, 1996), an effective P. multocida BRD vaccine is still lacking.…”

“…In Yersinia pseudotuberculosis and Vibrio cholerae, inactivation of the dam gene was shown to be a lethal mutation (Julio et al, 2001). However, plasmid-mediated overexpression of the dam gene in Y. pseudotuberculosis resulted in a >6000-fold increase in LD 50 in mice compared to wild-type and a fivefold defect in colonization of V. cholerae in a suckling mouse model compared to wild-type (Julio et al, 2001).…”

An orphan DNA (cytosine-5-)-methyltransferase in Vibrio cholerae

“…cholerae is a Gram-negative enteric pathogen that causes the diarrhoeal disease cholera (Kaper et al, 1995). DNA adenine methylation has been reported in V. cholerae, and a role of the V. cholerae DNA adenine methyltransferase (Dam) in virulence (Julio et al, 2001) and chromosome replication (Egan & Waldor, 2003) has been demonstrated. Although V. cholerae possesses an efficient Dam-directed mismatch repair pathway (Bera et al, 1989), it lacks homologues of Escherichia coli Dcm and Vsr endonuclease (Bhakat et al, 1999), known to be associated with the very short patch (VSP) repair system.…”