Protein profile of bacterial extracellular polymeric substance by Fourier transform infrared spectroscopy

Abstract

Self-adherent bacterial communities are embedded into biofilms, these densely packed and distinctive microbial matrices are surrounded by extracellular polymeric substances (EPS). The growth surface of bacteria, environmental conditions and harvesting methods may alter the biochemical composition of secreted EPS and the selection of EPS isolation method has critical role on analysis. In the present study, EPS produced by various strains were extracted using two extraction methods including liquid (broth) or solid (agar) media. The biomolecular content of resulting extracts were investigated for comparative analysis of different EPS isolation methods. EPS composition of each strain was analyzed by Fourier transform infrared spectroscopy (FTIR), a non-common technique for foodborne pathogen researches. According to the FTIR analysis results of the samples extracted by liquid media technique, some additional peaks were observed at 1397 cm−1 and 1230 cm−1. These peaks cannot be observed for solid media samples, two of the molecular fingerprints were disappeared and the protein content have found decreased. Similar results obtained from conventional protein assay (Bradford), 8 out of 10 samples of liquid extraction method were also shown to be significantly higher in comparison solid extraction method (p < 0.05). These findings confirm the feasibility of FTIR for EPS researches and importance of method selection for the detection of biomolecular fingerprints.