RNA/DNA ratio as an indicator of metabolic activity in resin acid-degrading bacteria

We investigated the relationship between the growth rate and the ratio of RNA to DNA in of four resin acid degrading bacteria isolated from a sequencing batch reactor (SBR). Chemical assays as well as slot blot hybridizations with species-specific oligonucleotide probes were used to quantify the nucleic acids. These slow-growing bacteria have a positive linear correlation between growth rate and RNA/DNA ratio, similar to faster-growing bacteria like E. coli. We propose to use this correlation to measure metabolic activities of selected resin acid degrading bacteria in the complex community of the SBR in situ using species-specific hybridization probes. Preliminary experiments suggest that hybridization probes can be used to detect growth rate-dependent changes in the RNA/DNA ratio.