The influence of calcium on biofilm processes

Abstract

Bacteria exhibit a tendency for adsorbing to and colonizing surfaces which are submerged in aquatic environments. Adsorption is mediated by extracellular polymeric material which is formed by the bacteria and extends from the cell to the attachment surface. The attached cells reproduce and form additional extracellular polymer increasing the mass of the deposit. The cellular-extracellular matrix is termed a bipfilm. The purpose of this study was to investigate the effect of calcium on cellular reproduction and extracellular polymer formation by Pseudomonas aeruginosa in a biofilm. Experiments were conducted with a pure culture of Ps. aeruginosa using fixed film bioreactors with glucose serving as the limiting nutrient. Results indicate calcium increases the rate and extent of cellular carbon accumulation at the surface. However, there was no effect of calcium on the amount of polymer carbon accumulated on the surface. Results also suggest that free calcium (or calcium assisted ligands) is essential to the structural integrity of the biofilm. The energy required for biochemical conversion of glucose into biomass by suspended or immobilized culture of Ps. aeruginosa was constant and was independent of time, biomass concentration, specific cellular growth rate, and calcium concentration in the medium.