STRUCTURE AND ACTIVITY OF PSEUDOMONAS AERUGINOSA PAO1 BIOFILMS by Raaja Raajan

Nutrient concentration profiles are affected by the mass transport outside the biofilm, inside the biofilm, and by the structure of the biofilm. To understand the distribution of biofilm activity, it is necessary to correlate the local nutrient concentration, local mass transport in the biofilm and the biofilm structure. The correlations among surface averaged dissolved oxygen concentration, surface averaged relative effective diffusivity, and areal porosity in the biofilms of Pseudomonas aeruginosa PAO1 grown in a flat plate reactor, were quantified. Three dimensional distributions of local dissolved oxygen concentration, local relative effective diffusivity, and porosity in the biofilm were measured. It was found that the local dissolved oxygen concentrations and relative effective diffusivities correlate weakly with each other or with the areal porosity. However surface averaged dissolved oxygen concentration and surface averaged relative effective diffusivity strongly correlated with each other and with the areal porosity. The surface averaged dissolved oxygen concentration, surface averaged relative effective diffusivity, and areal porosity decreased towards the bottom of the biofilm, while the coefficients of variation computed for each of these parameters increased towards the bottom of the biofilm. The coefficient of variation is quantified as a measure of the heterogeneity of the biofilm. The increase in the coefficient of variation shows that the heterogeneity of the biofilm increases towards the bottom of the biofilm.