Isolation of the Bacteriophage DinoHI from 'Dichelobacter nodosus' and its Interactions with other Integrated Genetic Elements

The Gram-negative anaerobic pathogen 'Dichelobacter nodosus' carries several genetic elements that integrate into the chromosome. These include the 'intA', 'intB', 'intC' and 'intD' elements, which integrate adjacent to 'csrA' and 'pnpA', two putative global regulators of virulence and the virulence-related locus, 'vrl', which integrates into 'ssrA'. Treatment of 'D. nodosus' strains with ultraviolet light resulted in the isolation of DinoHI, a member of the 'Siphoviridae' and the first bacteriophage to be identified in 'D. nodosus'. Part of the DinoHI genome containing the packaging site is found in all 'D. nodosus' strains tested and is located at the end of the 'vrl', suggesting a role for DinoHI in the transfer of the 'vrl' by transduction. Like the intB element, the DinoHI genome contains a copy of 'regA' which has similarity to the repressors of lambdoid bacteriophages, suggesting that the maintenance of DinoHI and the intB element may be co-ordinately controlled.