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

Designation	Description	Mechanism 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 probe	Cell binding by rhodamine part of probe
Nnon,unl	Number of cells hybridized with labelled nonspecific probe and excess of unlabelled nonspecific probe	Cell 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