Basis for the mutational acquisition of the ability of Aerobacter aerogenes to grow on L-mannose.
Growth of Aerobacter aerogenes PRL-R3 on the unnatural hexose l-mannose as a sole carbon source is dependent upon the selection of a mutant. Growth of the mutant on l-mannose did not require the synthesis of novel enzymes for the degradation of l-mannose, since enzymes of the l-rhamnose degradative pathway could serve this function. However, unlike most other apparent gain mutations that have been described, the mutant was not constitutive for the degradative enzymes; isomerase, kinase, and aldolase activities functional in the degradation of both l-mannose and l-rhamnose were induced by either of these hexoses in the wild type as well as in the mutant. The fact that the wild type could metabolize l-mannose also ruled out the possibility that the cells were not permeable to l-mannose. Growth of the wild type on nutrient broth was severely inhibited by l-mannose coincident with the onset of l-mannose metabolism. A similar inhibition of growth of the mutant was overcome in about 2 hr. Both strains utilized l-rhamnose and l-mannose sequentially in a mineral medium containing both of these hexoses; at the onset of l-mannose metabolism, growth of the wild type, but not of the mutant, was inhibited. Thus, wild-type A. aerogenes cannot grow on l-mannose because of the toxicity of l-mannose or its metabolites. A mutation which overcomes the toxicity enables the organism to utilize l-mannose as a sole source of carbon and energy for growth.
D003470:Culture Media; D004754:Enterobacter / Q000201:enzymology / Q000254:growth & development*; D005634:Fructose-Bisphosphate Aldolase / Q000378:metabolism; D005827:Genetics, Microbial; D007535:Isomerases / Q000378:metabolism; D008358:Mannose / Q000378:metabolism*; D008365:Manometry; D008722:Methods; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D010770:Phosphotransferases / Q000378:metabolism; D012210:Rhamnose / Q000378:metabolism
D003470:Culture Media; D009153:Mutagens; D010770:Phosphotransferases; D005634:Fructose-Bisphosphate Aldolase; D007535:Isomerases; D008358:Mannose; D012210:Rhamnose