Table 1.

Model for calculating numbers of actively growing bacteria in soil, as determined by a slurry in situ hybridization protocol performed with rhodamine-labelled oligonucleotide probes targeting rRNA and controls containing excess unlabelled probe

DesignationDescriptionMechanism of binding
Cell numbers measured
 Nsp Number of cells hybridized with specific rhodamine-labelled probe (EUB338)Homologous and heterologous hybridization to rRNA and cell binding by DNA and rhodamine parts of probe
 Nnon Number of cells hybridized with nonspecific rhodamine-labelled probe (NONEUB338)Heterologous hybridization to rRNA and cell binding by DNA and rhodamine parts of probe
 Nsp,unl Number of cells hybridized with labelled specific probe and excess of unlabelled specific probeCell binding by rhodamine part of probe
 Nnon,unl Number of cells hybridized with labelled nonspecific probe and excess of unlabelled nonspecific probeCell binding by rhodamine part of probe
Cell numbers calculated
 Nsp − Nsp,unl Homologous and heterologous hybridization to rRNA and cell binding by DNA part of probe
 Nnon − Nnon,unl Heterologous hybridization to rRNA and cell binding by DNA part of probe
 (Nsp − Nsp,unl) − (Nnon − Nnon,unl)Homologous hybridization to rRNA