Biochemical and Genetic Studies with Lysine + Methionine Mutants of Escherichia coli: Lipoic Acid and  -Ketoglutarate Dehydrogenase-less Mutants

SUMMARY: A selection procedure was developed for the isolation of mutants of Escherichia coli which require lipoic acid, acetate+succinate, or lysine + methionine for aerobic growth with glucose. The properties of the mutants requiring lipoic acid (lip −) were compared with those of suc − mutants which lack α-ketoglutarate dehydrogenase and require succinate or lysine + methionine. Genetic analysis by conjugation with Hfr and F’ donors indicated that the genetic loci of some 36 independently isolated lip − mutants are confined to a small segment of the E. coli chromosome between the purE and suc sites. By using phage P1 no cotransduction of lip with suc, glt A or purE could be demonstrated, but suc, gltA and gal were cotransducible and the relative order of these sites was determined.