Leiman, SaraMay, J. M.Lebar, M. D.Kahne, DanielKolter, R.Losick, Richard2017-11-022013Leiman, S. A., J. M. May, M. D. Lebar, D. Kahne, R. Kolter, and R. Losick. 2013. “D-Amino Acids Indirectly Inhibit Biofilm Formation in Bacillus Subtilis by Interfering with Protein Synthesis.” Journal of Bacteriology 195 (23) (October 4): 5391–5395. doi:10.1128/jb.00975-13.0021-9193http://nrs.harvard.edu/urn-3:HUL.InstRepos:34323222The soil bacterium Bacillus subtilis forms biofilms on surfaces and at air-liquid interfaces. It was previously reported that these biofilms disassemble late in their life cycle and that conditioned medium from late-stage biofilms inhibits biofilm formation. Such medium contained a mixture of d-leucine, d-methionine, d-tryptophan, and d-tyrosine and was reported to inhibit biofilm formation via the incorporation of these d-amino acids into the cell wall. Here, we show that l-amino acids were able to specifically reverse the inhibitory effects of their cognate d-amino acids. We also show that d-amino acids inhibited growth and the expression of biofilm matrix genes at concentrations that inhibit biofilm formation. Finally, we report that the strain routinely used to study biofilm formation has a mutation in the gene (dtd) encoding d-tyrosyl-tRNA deacylase, an enzyme that prevents the misincorporation of d-amino acids into protein in B. subtilis. When we repaired the dtd gene, B. subtilis became resistant to the biofilm-inhibitory effects of d-amino acids without losing the ability to incorporate at least one noncanonical d-amino acid, d-tryptophan, into the peptidoglycan peptide side chain. We conclude that the susceptibility of B. subtilis to the biofilm-inhibitory effects of d-amino acids is largely, if not entirely, due to their toxic effects on protein synthesis.en-USJournal Article2017-05-1120132017-11-0210.1128/JB.00975-13