Abstract
SUMMARY: Among temperature-sensitive mutants ofEscherichia colia strain was discovered requiring D-alanine for growth. It was proved to possess an altered alanine racemase. The structural gene for this enzyme, designatedalr, is located betweenmetBandpur A. The properties of the enzyme and its locus suggest that it is not under control of the mechanisms which regulate mucopeptide formation. A suppressor of thealrmutation was discovered neartrp, and termedmsuA.