ABSTRACT
Biofilms cause biocorrosion and biofouling. Biocorrosion is a major problem in many industries such as oil and gas, as well as water utilities. Biomedical implants such as dental and orthopedic implants also encounter biocorrosion. All bacterial cell walls contain peptidoglycan molecules with peptide stems consisting of four alternating L- and D-amino acids. The peptide stems all have a D-alanine terminus. It has been hypothesized that replacing the D-alanine terminus with another D-amino acid sends a biofilm dispersal signal. Several recent journal papers presented experimental data showing that D-tyrosine, D-tryptophan, D-methionine, and D-leucine at low concentrations are capable of dispersing bacterial biofilms. It is well known that sessile cells in biofilms are far more difficult to mitigate than planktonic cells because biofilms have various defense mechanisms. Usually ten times or higher biocide concentrations are required to treat sessile cells compared with planktonic cells. Thus, converting sessile cells to planktonic cells is highly desirable in biofilm mitigation. This work presented experimental data showing that D-valine that is not among the aforementioned D-amino acids could also considerably enhance THPS (tetrakis hydroxymethyl phosphonium sulfate) biocide mitigation of the Desulfovibrio vulgaris>/i> biofilm, which is a tough and corrosive sulfate reducing bacterium biofilm. Using metronidazole as a representative clinical antibiotic, this work also demonstrated that a D-amino acid such as D-methionine could greatly enhance the mitigation of a recalcitrant biofilm such as the D. vulgaris biofilm. This points to a potential application in fighting biofilm problems involving biomedical implants.
