We have isolated Escherichia coli K-12 mutant YW201 that utilizes neither D-ribose nor succinate. It has a little growth defect on other sugars such as fumarate, maltose, glucuronate, fructose etc. It has one mutation somewhere in the region between 40.5 min and 43 min on the chromosome and the other mutation between 15 min and 19 min. The latter mutation in YW201 is primarily responsible for the growth defect on D-ribose or succinate. The mutation mapped in the region between 40.5 min and 43 min is closely linked to flhDC on the chromosome and is presumably suppressed by flhDC null mutation.