5'-Horseradish Peroxidase (HRP) labeling for in-situ hybridization is a very sensitvie detection and identification method for bacteria and eucaryotic cells. They are reported to have less background than using biotinylated probes with avidin(streptavidin)-HRP conjugates. Sensitivity is reportedly better with alkaline phosphatase labeled probes, but HRP probes generate signal rapidly and lots of systems are designed to work with them (chemiluminescence, etc).
Suggested Reference:
- A Pernthaler et.al., (2002) Fluorescence in -situ Hybridication and Catalyzed Reporter Deposition for the Identification of Marine Bacteria. Applied and Environmental Microbiology, Vol. 68, No. 6, pp. 3094-3101.