title: Selection procedure for mutants defective in the beta-methylgalactoside transport system of Escherichia coli utilizing the compound 2R-glyceryl-beta-D-galactopyranoside.
abstract: A procedure has been devised that allows selection of mutants defective in the beta-methylgalactoside transport system (mgl) of Escherichia coli. This procedure utilizes the compound 2R-glyceryl-beta-d-galactopyranoside (glycerylgalactoside), which is known to be transported by only two transport system in E. coli, namely, the lactose and the beta-methylgalactoside transport systems. Mutants lacking glycerol-3-phosphate dehydrogenase (glpD) are sensitive to glycerol. Similarly, mutants lacking uridine diphosphate-galactose-4-epimerase (galE) are sensitive to galactose. Glycerylgalactoside is an inducer of the lactose operon and also a substrate for beta-galactosidase. Thus, a mgl(+)glpD galE lacY strain will not grow in the presence of glycerylgalactoside owing to accumulated glycerol-3-phosphate, galactose-1-phosphate, and uridine diphosphate-galactose. We have constructed such a strain and shown that mgl mutants can be obtained by selecting for those that grow in the presence of glycerylgalactoside.
mesh_terms: D001345:Autoradiography; D001693:Biological Transport, Active; D002238:Carbohydrate Epimerases / Q000096:biosynthesis; D002250:Carbon Radioisotopes; D002854:Chromatography, Paper; D004926:Escherichia coli / Q000201:enzymology / Q000302:isolation & purification / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism; D005696:Galactosidases / Q000096:biosynthesis; D005990:Glycerol / Q000378:metabolism; D005993:Glycerolphosphate Dehydrogenase / Q000096:biosynthesis; D006027:Glycosides / Q000378:metabolism*; D007700:Kinetics; D008756:Methylgalactosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D009153:Mutagens; D009154:Mutation; D009604:Nitrosoguanidines; D013386:Succinates / Q000378:metabolism; D014161:Transduction, Genetic
chemical_list: D002250:Carbon Radioisotopes; D006027:Glycosides; D008756:Methylgalactosides; D008759:Methylglycosides; D009153:Mutagens; D009604:Nitrosoguanidines; D013386:Succinates; D005993:Glycerolphosphate Dehydrogenase; D005696:Galactosidases; D002238:Carbohydrate Epimerases; D005990:Glycerol; D005690:Galactose