Minimal essential medium metabolism

MEL Metabolic equivalent level MEM Minimal essential medium MG Myasthenia gravis MGSA Melanoma-growth-stimulatory activity MHC Major histocompatibility complex... 

The elucidation of the steps in the common part of the pathway from carbohydrate precursors to the formation of chorismate remains a classic example of the combined use of auxotrophic mutants, isotop-ically labelled precursors and finally enzyme studies to define a metabolic sequence. An auxotrophic mutant of an organism is a nutritional mutant. The genetic change in such mutant strains causes an inability to carry out one of the reactions in a biosynthetic pathway leading to one or more essential metabolites. Analysis of the sequence of steps in the biosynthetic pathway is facilitated by the fact that each mutant may accumulate in its culture fiuid the substrate for the enzymic reaction which is blocked and may utilise later members of the sequence to replace the required metabolites Davis S produced auxotrophic mutants of Escherichia coli, Aerobacter aerogenes. Bacillus subtilis and Salmonella typhitnurium by ultra-violet irradiation of a bacterial culture in a minimal medium of salts plus D-glucose. Selection of the mutant strains was dependent on the use of the observation that penicillin kills bacterial cells only... 

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