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d-Amino acids do not inhibit biofilm formation in Staphylococcus aureus.

Sarkar S, Pires MM - PLoS ONE (2015)

Bottom Line: Bacteria can either exist in the planktonic (free floating) state or in the biofilm (encased within an organic framework) state.Herein we show that, contrary to previously published reports, d-amino acids do not inhibit biofilm formation of Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Staphylococcus epidermis (S. epidermis) at millimolar concentrations.We evaluated a diverse set of natural and unnatural d-amino acids and observed no activity from these compounds in inhibiting biofilm formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania, United States of America.

ABSTRACT
Bacteria can either exist in the planktonic (free floating) state or in the biofilm (encased within an organic framework) state. Bacteria biofilms cause industrial concerns and medical complications and there has been a great deal of interest in the discovery of small molecule agents that can inhibit the formation of biofilms or disperse existing structures. Herein we show that, contrary to previously published reports, d-amino acids do not inhibit biofilm formation of Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Staphylococcus epidermis (S. epidermis) at millimolar concentrations. We evaluated a diverse set of natural and unnatural d-amino acids and observed no activity from these compounds in inhibiting biofilm formation.

No MeSH data available.


Related in: MedlinePlus

Control compounds effect on biofilm formation.S. aureus (SC01) biofilm formation was evaluated after 24 h (A) and 48 h (B) in the presence of D-amino acids previously reported as inhibitors at a concentration of 1 mM or the positive control carvacrol (2 mM). The absorbance was recorded at 595 nm following crystal violet staining. All points are significantly different from the positive control carvacrol (****p<0.0001) relative to positive control, unpaired t-test.).
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pone.0117613.g001: Control compounds effect on biofilm formation.S. aureus (SC01) biofilm formation was evaluated after 24 h (A) and 48 h (B) in the presence of D-amino acids previously reported as inhibitors at a concentration of 1 mM or the positive control carvacrol (2 mM). The absorbance was recorded at 595 nm following crystal violet staining. All points are significantly different from the positive control carvacrol (****p<0.0001) relative to positive control, unpaired t-test.).

Mentions: In order to evaluate the effect of D-amino acids on biofilm formation we initially used S. aureus (SC01 strain), the same strain that had been previously shown to be sensitive to D-amino acids [5]. In the initial report, D-tyrosine was reported to fully inhibit biofilm formation of S. aureus at 50 μM and the mixture of D-leucine/D-methionine/D-tyrosine/D-tryptophan at 15 nM each [4]. In a later report, the potency of D-tyrosine was revised. They found that D-phenylalanine, D-proline, and D-tyrosine were individually able to fully inhibit biofilm formation at 500 μM [5]. The combination of these three D-amino acids led to significant impairment at 10 μM and full inhibition at 100 μM [5]. Initially, we set out to reproduce these results as control compounds in inhibiting the formation of S. aureus biofilm as previously reported. We observed that D-tyrosine, D-tryptophan, and the equimolar mixture of D-tyrosine/D-proline/D-phenylalanine failed to inhibit biofilm formation at 1 mM (Fig. 1). Visual inspection of the biofilm confirmed that none of the compounds disrupted biofilm formation. Next, we doubled the incubation time to 48 hours to explore the possible inhibition by D-amino acids at longer incubation times. Clearly, the biofilms became denser at the 48-hour period as seen by the higher crystal violet-associated absorbance for all the compounds evaluated. Next, we evaluated the ability of D-amino acids to inhibit bacterial biofilm formation at 5 mM, which is ten times higher than the reported revised concentration for full inhibition and a hundred times higher than the initially reported concentration. For this series, only the reported biofilm inhibitors (D-tyrosine, D-tryptophan, and the equimolar mixture of D-tyrosine/D-proline/D-phenylalanine) were assessed at 5 mM. Following a 24 hour incubation period, there was no biofilm inhibition based on visual inspection and no significant inhibition was observed following staining (Fig. 2). Our data indicates that the D-amino acids evaluated herein show no activity in modulating the formation of S. aureus biofilm.


d-Amino acids do not inhibit biofilm formation in Staphylococcus aureus.

Sarkar S, Pires MM - PLoS ONE (2015)

Control compounds effect on biofilm formation.S. aureus (SC01) biofilm formation was evaluated after 24 h (A) and 48 h (B) in the presence of D-amino acids previously reported as inhibitors at a concentration of 1 mM or the positive control carvacrol (2 mM). The absorbance was recorded at 595 nm following crystal violet staining. All points are significantly different from the positive control carvacrol (****p<0.0001) relative to positive control, unpaired t-test.).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4319739&req=5

pone.0117613.g001: Control compounds effect on biofilm formation.S. aureus (SC01) biofilm formation was evaluated after 24 h (A) and 48 h (B) in the presence of D-amino acids previously reported as inhibitors at a concentration of 1 mM or the positive control carvacrol (2 mM). The absorbance was recorded at 595 nm following crystal violet staining. All points are significantly different from the positive control carvacrol (****p<0.0001) relative to positive control, unpaired t-test.).
Mentions: In order to evaluate the effect of D-amino acids on biofilm formation we initially used S. aureus (SC01 strain), the same strain that had been previously shown to be sensitive to D-amino acids [5]. In the initial report, D-tyrosine was reported to fully inhibit biofilm formation of S. aureus at 50 μM and the mixture of D-leucine/D-methionine/D-tyrosine/D-tryptophan at 15 nM each [4]. In a later report, the potency of D-tyrosine was revised. They found that D-phenylalanine, D-proline, and D-tyrosine were individually able to fully inhibit biofilm formation at 500 μM [5]. The combination of these three D-amino acids led to significant impairment at 10 μM and full inhibition at 100 μM [5]. Initially, we set out to reproduce these results as control compounds in inhibiting the formation of S. aureus biofilm as previously reported. We observed that D-tyrosine, D-tryptophan, and the equimolar mixture of D-tyrosine/D-proline/D-phenylalanine failed to inhibit biofilm formation at 1 mM (Fig. 1). Visual inspection of the biofilm confirmed that none of the compounds disrupted biofilm formation. Next, we doubled the incubation time to 48 hours to explore the possible inhibition by D-amino acids at longer incubation times. Clearly, the biofilms became denser at the 48-hour period as seen by the higher crystal violet-associated absorbance for all the compounds evaluated. Next, we evaluated the ability of D-amino acids to inhibit bacterial biofilm formation at 5 mM, which is ten times higher than the reported revised concentration for full inhibition and a hundred times higher than the initially reported concentration. For this series, only the reported biofilm inhibitors (D-tyrosine, D-tryptophan, and the equimolar mixture of D-tyrosine/D-proline/D-phenylalanine) were assessed at 5 mM. Following a 24 hour incubation period, there was no biofilm inhibition based on visual inspection and no significant inhibition was observed following staining (Fig. 2). Our data indicates that the D-amino acids evaluated herein show no activity in modulating the formation of S. aureus biofilm.

Bottom Line: Bacteria can either exist in the planktonic (free floating) state or in the biofilm (encased within an organic framework) state.Herein we show that, contrary to previously published reports, d-amino acids do not inhibit biofilm formation of Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Staphylococcus epidermis (S. epidermis) at millimolar concentrations.We evaluated a diverse set of natural and unnatural d-amino acids and observed no activity from these compounds in inhibiting biofilm formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania, United States of America.

ABSTRACT
Bacteria can either exist in the planktonic (free floating) state or in the biofilm (encased within an organic framework) state. Bacteria biofilms cause industrial concerns and medical complications and there has been a great deal of interest in the discovery of small molecule agents that can inhibit the formation of biofilms or disperse existing structures. Herein we show that, contrary to previously published reports, d-amino acids do not inhibit biofilm formation of Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Staphylococcus epidermis (S. epidermis) at millimolar concentrations. We evaluated a diverse set of natural and unnatural d-amino acids and observed no activity from these compounds in inhibiting biofilm formation.

No MeSH data available.


Related in: MedlinePlus