Impact of bacterial culture medium on composition and characteristics of Burkholderia pseudomallei extracellular polymeric substances

Extracellular polymeric substances (EPS) are essential for maintaining the structural integrity and function of biofilms. In this study, the influence of nutrient composition on biofilm formation and EPS production by Burkholderia pseudomallei was assessed using a quantitative assay after cultivation in brain heart infusion (BHI), Luria-Bertani (LB), and modified Vogel and Bonner medium (MVBM) for 2, 4 and 6 days. Biofilm biomass, the percentage of EPS in the biofilm matrix, and the biochemical composition of EPS were analyzed. The functional groups of EPS were characterized using Fourier transform infrared (FTIR) spectroscopy, while the microstructural features of the EPS were examined using scanning electron microscopy. We found that B. pseudomallei cultured in MVBM exhibited the highest biofilm biomass, despite having the lowest proportion of EPS within the biofilm matrix. In contrast, cultures in LB medium produced the lowest biofilm biomass but contained the highest percentage of EPS. These observations indicate that growth under high carbon/nitrogen (C/N) ratio, as in MVBM, favors biofilm biomass accumulation, whereas low C/N ratio conditions, such as LB and BHI, are associated with a high relative EPS content. Despite these differences, the carbon content of the EPS remained consistent across all media. Notably, the EPS derived from cultures grown in BHI, a nitrogen-rich medium, contained the highest protein content, which corresponded with noticeable amide peaks in FTIR spectra. Collectively, these findings enhance our understanding of how environmental C/N ratios influence B. pseudomallei biofilm development and EPS composition, with implications for bacterial persistence and adaptability in the environment.