ABSTRACT
Recently, CTC and DAPI staining was used to quantify the percentage of respiring aerobic and facultative anaerobic bacteria in biofilm samples. CTC will be reduced by dehydrogenases of respiring bacteria, forming an insolu ble, red fluorescent formazan crystal within the cell (Schaule et al., 1993; Rodriguez, 1992). DAPI binds non-specifically to all DNA molecules, induc ing a blue fluorescence (McFeters et al., 1995). Fluorescence-labeled 16S and 23S rRNA-directed oligonucleotides were used for in situ hybridization to quantify the occurrence of target sequences in a mixture of nucleic acids within a biofilm population (Amann et al., 1995; Manz et al., 1992; Manz et al., 1993). The presence of pathogenic or facultative pathogenic bacteria in young biofilms has been analyzed by amplification of rRNA-related sequences by polymerase chain reaction (PCR), followed by Southern blot hybridization with oligonucleotide probes specific for Legionella and fecal streptococci (Manz et al., 1995; Beimfohr et al., 1993; Betzl et al., 1990).
