ON LINE, NONDESTRUCTIVE BIOMASS DETERMINATION OF BACTERIAL BIOFILMS BY FLUOROMETRY

The lack of on-line methodology for the determination of microbial bio mass and activity of attached bacteria has severely limited the study of biofilm physiology. This study showed that the fluorescent emission of aromatic amino acids in microbial biofilms can be used to determin e the biomass formed on 316 stainless steel coupons. Cells resuspended from the substratum were enumerated by viable and acridine orange cou nts showing correlation coefficients of 0.77 and 0.98, respectively, w hen compared to the tryptophane fluorescence. Substrata treated with a fluorescent epoxy coating (F-150) showed no fluorescence that could b e attributed to the microorganisms. Bioluminescent emission of an acti vely growing bioluminescent bacterium, Vibrio harveyi, was correlated with acridine orange counts (r(2)=0.95) and fluorescence (r(2)=0.93). The results of these studies suggest that fluorescence measurements ca n be used to monitor microbial biomass associated with various substra ta. Coupled with bioluminescence measurements, this method provides in formation on both biomass constituents and metabolic activity, and the refore possibly an indicator of sub-lethal toxicity.