Calcium-mediated modulation of Pseudomonas mendocina NR802 biofilm influences the phenanthrene degradation

A potential biofilm forming and phenanthrene utilizing marine bacterium Pseudomonas mendocina NR802 was isolated from Rushukulya, Odisha, East Coast of India. The effect of Ca2+ and Mg2+ on biofilm growth and phenanthrene degradation was evaluated. Among the various tested concentrations, 20 mM of Ca2+ and Mg2+ showed a significant enhancement in biofilm production by the bacterium. The SEM-EDAX study showed that the elemental composition of the biofilm varied significantly when grown in the presence of Ca2+ and Mg2+. The CSLM analysis of biofilms grown in the presence of 20 mM Ca2+ and Mg2+ reveal the critical role of these ions on biofilm architectural parameters such as total biomass, biofilm thickness, roughness coefficient and surface to biovolume ratio. Ca2+ was found to enhance the extracellular polymeric substances (EPS) production and phenanthrene degradation. Ca2+ enhanced the biofilm growth in a dose dependent manner, whereas Mg2+ significantly increased the cell growth in biofilm. More than 15% increase in phenanthrene degradation was observed when biofilm was grown in the presence of an additional 20 mM Ca2+. This study also supports the fundamental role of Ca2+ in biofilm growth, architecture as well as biofilm-mediated pollutant degradation.