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

Abstract

Pasteurella multocidais one of the primary bacterial pathogens associated with bovine respiratory disease (BRD) complex. Relatively few virulence factors ofP. multocidahave been characterized, and there is a need for improved vaccines for prevention of BRD. In other Gram-negative species, DNA adenine methylase (Dam) regulates the expression of virulence genes, and appropriate expression of Dam is required for virulence. In this study, the authors cloned and sequenced theP. multocidaA1damgene and demonstrated that it is able to restore Dam function in anEscherichia coli dammutant. WhenP. multocida damwas placed under the control of a constitutively expressed promoter on a plasmid, it caused an increased spontaneous mutation rate inP. multocida. In addition, the plasmid-mediated alteration of Dam production inP. multocidacaused it to be highly attenuated in mice. These findings indicate that appropriate expression of Dam is required for virulence ofP. multocida, which is believed to be the first report that Dam is required for virulence of a species in thePasteurellaceae. Therefore, Dam may function as a virulence gene regulator in thePasteurellaceae, similar to previously reported findings from other Gram-negative species.