Discovery, purification, and characterization of a temperate transducing bacteriophage for Bordetella avium

We discovered and characterized a temperate transducing bacteriophage (Ba1) for the avian respiratory pathogen Bordetella avium. Ba1 was initially ide ntified along with one other phage (Ba2) following screening of four strain s of B. avium for lysogeny. Of the two phage, only Ba1 showed the ability t o transduce via an allelic replacement mechanism and was studied further. W ith regard to host range, Ba1 grew on six of nine clinical isolates of B. a vium but failed to grow on any tested strains of Bordetella bronchiseptica, Bordetella hinzii, Bordetella pertussis, or Bordetella parapertassis. Ba1 was purified by CsCl gradient centrifugation and was found to have an icosa hedral head that contained a linear genome of approximately 46.5 kb (contou r length) of double-stranded DNA and a contractile, sheathed tail. Ba1 read ily lysogenized our laboratory B. avium strain (197N), and the prophage sta te was stable for at least 25 generations in the absence of external infect ion. DNA hybridization studies indicated the prophage was integrated at a p referred site on both the host and phage replicons. Bal transduced five dis tinctly different insertion mutations, suggesting that transduction was gen eralized. Transduction frequencies ranged from approximately 2 x 10(-7) to 1 x 10(-8) transductants/PFU depending upon the marker being transduced. UV irradiation of transducing lysates markedly improved transduction frequenc y and reduced the number of transductants that were lysogenized during the transduction process. Ba1 may prove to be a useful genetic tool for studyin g B. avium virulence factors.