Characterization and physical mapping of the genome of bacteriophage phi Aa from Actinobacillus actinomycetemcomitans

The size, configuration and restriction map of Actinobacillus actinomycetemcomitans bacteriophage phi Aa DNA was determined by means of restriction endonuclease analysis. Digestion of the phi Aa DNA with restriction enzymes Hind III, Eco RI and Sal I produced 6, 5, and 4 fragments, respectively. Based upon the sum of the sizes of the restriction fragments of these enzymes, the DNA was estimated to be 47.2 kilobase pairs in length. A restriction map was constructed using Hind III and Sal I. Incubation with exonuclease Bal 31 for increasing lengths of time resulted in progressive hydrolysis of the DNA, as expected for a linear molecule. No sub-molar fragments or diffuse bands were observed in the agarose gels of the restriction endonuclease digests of the phi Aa DNA. Attempts at ligating the ends of the DNA were consistently unsuccessful. Therefore, we found no evidence for cohesive ends, a circular permutation of the genome or for headful packaging mechanism from a concatameric DNA precursor.