D-fining DarR: a LysR-type transcriptional regulator that responds to D-aspartate

Work by Jones et al. (R. M. Jones, Jr., D. L. Popham, A. L. Schmidt, E. L. Neidle, and E. V. Stabb, J Bacteriol 200:e00773-17, 2018, https://doi.org/10.1128/JB.00773-17) describes a d-aspartate-sensing system in proteobacteria. d-Amino acids are critical components of peptidoglycan and other structures. The new study identifies the LysR-type transcriptional regulator DarR, which activates the aspartate racemase RacD. The overexpression of RacD enables it to synthesize d-glutamate and restore normal peptidoglycan in a Vibrio fischerimurI mutant. This study contributes to the understanding of emerging roles for d-amino acids and how they are synthesized under distinct conditions.