ABSTRACT
Horizontal sections of a biofilm taken by a confocal laser-scanning micro scope can be stored in a digital format and used to calculate the area taken up by biological structures. Here we used the autofluorescence of a strain of Pseudom onas flu orescen s to follow the development of a biofilm in a flow cell. By integrating a number of optical sections, one can obtain an estimate of the biovolume in a biofilm. We chose a geometrical approach to be inde pendent of the number of data points. Instead of using autofluorescence, one could stain the biofilm and count specific cells or label other biological struc tures (Kuehn et al., 1998). Other approaches have relied on the delineation and edge detection of single cells after staining (Moller et al., 1995). Our method does not depend on the detection o f individual cells, which is diffi cult in biofilms containing several cell layers. By computing the area or vol ume taken up by specific cells based on their fluorescence and comparing it to the overall cellular volume it will be possible to construct depth-resolved profiles o f any microbial population without the need for cell counts. This should simplify the study of biofilms considerably because automated counts can be performed randomly.
