Effects of Bacillus Serine Proteases on the Bacterial Biofilms

Figure 6

Bacillus proteases effectively destroy S. marcescens biofilms. ((a)–(c)) SEM micrographs illustrating S. marcescens biofilms degradation by Bacillus proteolytic enzymes. (a) Nontreated biofilms (biofilms incubated with 0.05 M Tris-HCl buffer). (b) Biofilms treated with subtilisin-like protease at 0.5 U/ml. (c) Biofilms treated with glutamyl endopeptidase at 0.1 U/ml. Images were taken at 5,000x magnification. Bars: 1 μm. (d) Quantitative analysis of the 7-day-old S. marcescens biofilms’ biomass after the protease treatment. Established biofilms were treated with subtilisin-like protease at 0.5 U/ml and glutamyl endopeptidase at 0.1 U/ml for 12 h at 37°C. Biofilms treated with 0.05 M Tris-HCl, pH 8.5, were used as a control. Experiment was performed in triplicate and repeated twice. Each bar represents the average of three experiments, with error bars representing the standard deviations. (e) Protein concentration in the EPS extracted from the protease-treated and untreated S. marcescens biofilms. Protein concentrations in the collected EPS extracts were quantified in Bradford assay. Experiment was performed in duplicate and repeated twice. Each bar represents the average of two experiments, with error bars representing standard deviations. Asterisk indicates statistical significance in Student’s -test with .

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