Characterization and Evaluation of Biofilm Formation by Klebsiella pneumonia MBB9 Isolated from Epilithic Biofilms of the Porter Brook River, Sheffield

Abstract

Microbes generally attach to surfaces and produce an Extracellular Polymeric Substance (EPS) matrix. The exopolysaccharide production plays a role in biofilm protection against environmental stress factors. Biofilm-forming bacteria exhibit different physiological properties in their response to environmental influences compared with their planktonic counterparts. This study aimed to investigate the impact of changing the concentrations of glucose, peptone, and yeast extract and environmental parameters, such as temperature, pH, anaerobic conditions, osmotic stresses, and growth media on biofilm formation by K. pneumonia MBB9 recovered from river-stones collected from the Porter Brook, Sheffield using crystal violet and resazurin assays in microtiter plates. The different concentrations of glucose (0.25, 0.5 and 1 g L-1), peptone (0.25, 0.5 and 1 g L-1) and yeast extract (0.25, 0.5 and 1 g L-1) as carbon and nitrogen sources found to have an impact on biofilm formation by K. pneumonia MBB9. The greatest biomass level being at 0.25 g L-1 for glucose whereas the density of biofilm increased significantly with increasing the concentration of peptone and yeast extract until 1 g L-1 of peptone and yeast extract, suggesting that higher levels of peptone and yeast extract can be beneficial for biofilm formation by K. pneumonia MBB9 in microtiter plates. The amount of biofilm was high at pH 4.5 and 0.6% NaCl; however, the significant reduction at pH 10.5 and 10.6% NaCl could be as a result of the slow growth under higher NaCl concentrations and highly alkaline condition. High-density biofilm produced at 40 °C; however, a temperature of 50 °C reduced the amount of biofilm by K. pneumonia MBB9, suggesting that more extreme temperatures might affect the formation of biofilm by inhibiting growth. Besides, biofilm production under anaerobic conditions was significantly lower (83% less) than under aerobic environments. Klebsiella pneumonia MBB9 possessed a high capacity to form biofilms on the surface of glass slide coupons.