A mutant of Mycobacterium smegmatis defective in dipeptide transport.

A mutant of Mycobacterium smegmatis unable to use the dipeptide carnosine (beta-alanyl-L-histidine) as a sole carbon or nitrogen source was isolated. Carnosinase activity and the ability to grow on beta-Ala and/or L-His were similar in the mutant and the wild type. However, the mutant showed significant impairment in the uptake of carnosine. This study is the first description of a peptide utilization mutant of a mycobacterium.