title: Methyl galactosidase activity: an alternative evolutionary destination for the ebgA0 gene.
abstract: Previous studies (Campbell et al., 1973; Hall and Hartl, 1974; Hall and Hartl, 1975) have shown that the ebgA0 gene, whose product does not hydrolyze lactose may evolve so that its product does hydrolyze lactose; i.e., lactase activity is one evolutionary destination of the ebgA0 gene. Beginning with a strain that synthesizes ebgA0 gene product constitutively and grows extremely slowly (doubling time, 30 to 50 h) on methyl-beta-D-galactopyranoside (MG), a derivative was selected capable of growth on MG at a moderate rate (doubling time, 5.9 h). Genetic evidence is presented showing that the gene that permits growth on MG is an allele of ebgA. A comparison among strains bearing several alleles of ebgA shows that the new allele, termed ebgAmg, synthesizes a product specific for MG and thus represents a true alternative evolutionary destination for the ebgA0 gene.
mesh_terms: D000483:Alleles; D005075:Biological Evolution; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D005285:Fermentation; D005696:Galactosidases / Q000378:metabolism*; D005796:Genes; D006868:Hydrolysis; D007785:Lactose / Q000378:metabolism; D008756:Methylgalactosides / Q000378:metabolism; D009154:Mutation
chemical_list: D008756:Methylgalactosides; D005696:Galactosidases; D007785:Lactose