An Escherichia coli mutant pleiotropically altered in membrane‐bound oxidoreductase activities was isolated following nitrosoguanidine treatment. Mutant R23 was able to grow on glucose, but was unable to grow on succinate or other oxidizable substrates as a sole energy source. Isolated membranes prepared from R23 failed to oxidize succinate and formate; while NADH was oxidized at a reduced rate by membranes. The mutant also exhibited markedly reduced cytochrome content, but normal DL‐lactate PMS reductase and H+‐translocating ATPase activities relative to the parent strain. Bacteriophage P1kc was used to transduce R23 to growth on glycerol, DL‐lactate or succinate; regardless of the selection procedure, each of the 179 transductants had gained the ability to grow on all three substrates. The suc− mutation in R23 appeared to be responsible for the loss of growth on oxidizable substrates, altered membrane‐bound oxidoreductase activities, resistance to neomycin, and reduced levels of cytochrome components. The suc− mutation was localized in the 6 to 6.5 min region of the E. coli chromosome map utilizing episomal transfers.