INTERRUPTION OF THE PHOSPHOGLUCOSE ISOMERASE GENE RESULTS IN GLUCOSE AUXOTROPHY IN MYCOBACTERIUM-SMEGMATIS

Two glycerol utilization mutants of Mycobacterium smegmatis that were unable to utilize most carbon sources except glucose were isolated. Su pplementation of these media with small amounts of glucose restored gr owth in the mutants; these strains are therefore glucose auxotrophs. T he mutant phenotype is complemented by the gene encoding phosphoglucos e isomerase (pgi), and direct measurement of enzyme activities in the mutants suggests that this gene product is absent in the auxotrophic s trains. Mapping of the mutant allele by Southern analysis demonstrates the presence of a I-kb deletion extending into the coding sequence of pgi. The possible roles of phosphoglucose isomerase in mycobacterial cell wall synthesis and metabolic regulation are discussed.