Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and Congo red and Calcofluor binding assays were used to identify the components of the biofilm matrices, i.e., EPS. For the FTIR analysis, the pellets were prepared as described in Mosharaf et al. (2018) (link). Using the triglycine sulfate (TGS) detector, 450 to 4000 cm–1 was scanned (16 scans at 4 cm–1 resolution and at 0.2 cm sec–1 scanning speed). The IR spectra of the biofilm matrices were acquired using the Perkin Elmer FTIR (Spectrum-2) instrument operated by CPU32M software. Perkin Elmer’s proprietary software (Version 10.05.03) was used to analyze the baseline subtracted biofilm spectra. For SEM, 72-hour-old biofilms were carefully collected and then oven dried at 40°C for 48 h. Each dried sample was coated with carbon using a vacuum sputter-coater to improve the conductivity. A scanning electron microscope (SEM, JEOL JSM-6490LA, Japan) operated at 5.0 KV was used to image the samples. To detect curli fimbriae and nanocellulose, Congo red and Calcofluor binding assays were performed as described in Haque et al. (2009 (link), 2017) (link).
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