Staphylococcus epidermidis is an opportunistic pathogen, and its biofilm formation ability is an important virulent factor. Quercetin, a typical flavonoid ubiquitously used in dietary supplementation, is known for its antioxidant property, but its anti-biofilm activity against S. epidermidis remains unknown. In this study, the anti-biofilm activity of quercetin was investigated using S. epidermidis ATCC35984, a strong biofilm-positive strain. An attempt was made to disclose the mechanisms of the anti-biofilm activity of quercetin. S. epidermidis exhibited a less cell surface hydrophobicity after quercetin treatment. Also, quercetin effectively inhibited S. epidermidis cells from adhering to the glass slides. Quercetin downregulated the intercellular adhesion (ica) locus and then polysaccharide intercellular adhesin (PIA) production was reduced. Therefore, S. epidermidis cells became less hydrophobic, which supported quercetin’s anti-biofilm effect. Our study suggests that quercetin from plants be given further attention as a potential anti-biofilm agent against the biofilm formation of S. epidermidis, even biofilm infections of other bacteria.

The enzyme protein-farnesyl transferase (PFTase) catalyzes the farnesylation of the Ras protein and certain other proteins, using farnesyl diphosphate (FPP) as the prenyl source. Because of the important role of mutant Ras proteins in cancer, inhibitors of PFTase are of great interest as potential novel anticancer agents. The design of such agents would be aided by a greater knowledge of the mechanism of PFTase. We have determined the stereochemical course of PFTase using the two stereospecifically prepared isomers of [1-2H]-FPP as substrates in conjunction with 1H-NMR analysis of the farnesylated peptide products. This confirms that PFTase carries out the transfer of the farnesyl group with inversion of configuration. Combined with the results of studies on fluorinated analogs of FPP as PFTase substrates (Dolence, J. M.; Poulter, C. D. Proc. Natl. Acad. Sci. U.S.A. 1995, 92, 5008), this indicates that the mechanistic course of PFTase is similar to that of the prototypical prenyltransferase enzyme, FPP synthase.

Aim The objective of this study was to investigate the biofilm inhibitory activity of Streptomyces‐derived actinomycin D against biofilm formation by Staphylococcus epidermidis. Methods and Results The microtitre plate method and microscopy were used to detect the biofilm formation of S. epidermidis. And an attempt was made to detect the effect of actinomycin D on important biofilm components, exopolysaccharides (EPS) in S. epidermidis using precolumn derivation HPLC. Also cell surface hydrophobicities of S. epidermidis were assessed to explore action mechanisms. The qPCR was performed to demonstrate the genetic mechanisms of biofilm formation by S. epidermidis. Unlike other antibiotics, actinomycin D (1·5 μg ml−1) from Streptomyces luteus significantly inhibited biofilm formation by S. epidermidis. Additionally, it effectively inhibited S. epidermidis cells from adhering to glass slides. Actinomycin D downregulated ica locus and then the reduced polysaccharide intercellular adhesin production caused S. epidermidis cells to become less hydrophobic, thus supporting its anti‐biofilm effect. Conclusion Streptomyces‐derived actinomycin D is active in inhibiting the biofilm formation of S. epidermidis. Significance and Impact of the Study Actinomycin D can be used as a promising antibiofilm agent in inhibiting S. epidermidis biofilm formation. The study is also the first insight into how actinomycin D inhibited the biofilm formation of S. epidermidis. Actinomycin D could potentially be used to reduce the risk of biofilm‐associated infections. Our study also suggests that the metabolites from Actinomycete strains keep further attention as potential antibiofilm agents against biofilm formation of S. epidermidis, even biofilm infections of the other bacteria.