USE OF RIBOSOMAL-RNA FLUORESCENCE INSITU HYBRIDIZATION FOR MEASURING THE ACTIVITY OF SINGLE CELLS IN YOUNG AND ESTABLISHED BIOFILMS

We describe the in situ use of rRNA-targeted fluorescent hybridization probes in combination with digital microscopy to quantify the cellula r content of ribosomes in relationship to the growth rate of single ce lls of a specific population of sulfate-reducing bacteria in multispec ies anaerobic biofilms. Using this technique, we inferred that this po pulation was growing with an average generation time of 35 h in a youn g biofilm, whereas the doubling time in an established biofilm was sig nificantly longer. Conventional chemical determinations of the RNA, DN A, and protein contents of this culture at different growth rates were also carried out, and the resulting data were compared with the rRNA fluorescence in situ hybridization data.