QUANTITATIVE-DETERMINATION OF THE SPATIAL-DISTRIBUTION OF NITROSOMONAS-EUROPAEA AND NITROBACTER-AGILIS CELLS IMMOBILIZED IN KAPPA-CARRAGEENAN GEL BEADS BY A SPECIFIC FLUORESCENT-ANTIBODY LABELING TECHNIQUE

A novel technique, combining labelling and stereological methods, for the determination of spatial distribution of two microorganisms in a b iofilm is presented. Cells of Nitrosomonas europaea (ATCC 19718) and N itrobacter agilis (ATCC 14123) were homogeneously distributed in a K-c arrageenan gel during immobilization and allowed to grow out to coloni es. The gel beads were sliced in thin cross sections after fixation an d embedding. A two-step labelling method resulted in green fluorescent colonies of either N. europaea or N. agilis in the respective cross s ections. The positions and surface areas of the colonies of each speci es were determined, and from that a biomass volume distribution for N. europaea and N. agilis in kappa-carrageenan gel beads was estimated. This technique will be useful for the validation of biofilm models, wh ich predict such biomass distributions.