Metabolism of Lactose by Staphylococcus aureus and Its Genetic Basis

The metabolism of lactose was found to be controlled by three genes: a gene for the synthesis of a β-galactosidase attacking only phosphorylated galactosides; a gene for a protein permitting concentration of phosphorylated galactosides which probably acts by transferring phosphates to them; and a gene regulating the first two structural genes. The three genes are closely linked and may have the same order as in Escherichia coli . Galactose-6-phosphate was found to be a better inducer of lactose utilization than is galactose or any other inducer. The inhibition of induction by isopropylthiogalactoside was found to occur at the level of the protein permitting the concentration of galactoside phosphates.