The amount of galactose genetic material in λ dg bacteriophage with different densities

Abstract

Previous work has shown that the buoyant density of different λdg phages varies widely. We aimed to find out if there are any λdg phages that carry only a part of the gal operon (i.e. the genes for galactokinase, transferase and epimerase), and if there is any relation between the density of a λdg phage and the amount of gal operon it carries. No matter what the density of the phage, most λdg in a low frequency transducing lysate were found to contain the entire set of three genes for galactose metabolism. However, about 10% of the λdg phages were found to have deletions in this set of genes. These defects are all in the galactokinase gene and range from a small deletion to the deletion of practically the entire galactokinase gene. The deletions all begin at one end of the galactokinase gene. For several of the λdg with gal deletions, the size of the λ deletion was determined by Dr. Allan Campbell. There is no relation between the size of the λ deletion and the size of the gal deletion. The density of a λdg phage appears to be determined by the size of its λ deletion and by the amount of the bacterial gal operon incorporated.