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J Bacteriol. 2013 Dec;195(23):5391-5. doi: 10.1128/JB.00975-13. Epub 2013 Oct 4.

D-amino acids indirectly inhibit biofilm formation in Bacillus subtilis by interfering with protein synthesis.

Author information

1
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA.

Abstract

The 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.

PMID:
24097941
PMCID:
PMC3837952
DOI:
10.1128/JB.00975-13
[Indexed for MEDLINE]
Free PMC Article

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