Staphylococcal biofilms were grown as follows: single colonies grown on BHI plates were inoculated into 3 ml of BHI medium and incubated overnight at 37°C with shaking. The overnight cultures were 1000-fold diluted in 10 ml of BHIG medium in a conical tube (15 ml, Becton Dickinson) and were incubated at 37°C for 24 h under static conditions. After the incubation, the conical tubes were centrifuged at 8000 g for 10 min at 25°C, and the supernatants were discarded completely. To extract ECM components, the residual pellets were suspended with the indicated regents (100 μl) at various concentrations. The suspensions were centrifuged at 5000 g for 10 min at 25°C, and the supernatants were transferred to a new test tube (1.5 ml) as ECM fractions (Fig. S1B). If required, the suspensions were incubated for the indicated periods at 25°C before centrifugation.
Escherichia coli and P. aeruginosa colony biofilms were cultivated on YESCA agar plates at 25°C for 72 h and on LB agar plates at 37°C for 24 h respectively. After the incubation, the colony biofilms were scraped with a scraper and suspended with 1 ml of 1.5 M NaCl solution. These suspensions were centrifuged at 5000 g for 10 min at 25°C without any incubation period. The supernatants were harvested as ECM fractions.
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