The chemistry of amino acids comes in two chirally distinct flavors—so-called L- and D-enantiomers. By far the most commonly used form of amino acids in all kingdoms of life is the L-form. Now Lam et al. (see the Perspective by Blanke) present the unanticipated observation that diverse bacteria release large amounts of various D-amino acids into the environment in a population density–dependent manner and that D-amino acids act as extracellular effectors that regulate the composition, structure, amount, and strength of peptidoglycan, the major stress-bearing component of the bacterial cell wall.
H. Lam, D.-C. Oh, F. Cava, C. N. Takacs, J. Clardy, M. A. de Pedro, M. K. Waldor, D-amino acids govern stationary phase cell wall remodeling in bacteria. Science 325, 1552–1555 (2009). [Abstract] [Full Text]