Automatic counting of FISH-labeled microbes by an LED illuminated detecting apparatus

The Bioplorer (BP) (Matsushita Ecology Systems Co. Ltd, Kasugai, Aichi-ken, Japan) is an apparatus that consists of a light-emitting diode and optical and image analysis systems. This instrument has been developed and used for the semi-automatic counting of total microbes, mainly in food, cosmetics and industrial products. In this study, the applicability of BP to the detection and enumeration of eukaryotic and prokaryotic cells, after the fluorescent in situ hybridization (FISH) procedure, was examined. The cells of a yeast (Candida albicans) and a bacterium (Escherichia coli) were specifically labeled using an oligonucleotide probe with fluorochrome and then counterstained with 4', 6-diamidino-2-phenylindole (DAPI). The numbers of cells after FISH treatment and DAPI staining agreed well, indicating that the BP optical device and image analysis system had enough sensitivity to detect and quantify eukaryotic and prokaryotic cells. Because of its simplicity and reliability, BP can be a new tool for quantification of specifically labeled target microorganisms, both in industrial products and natural samples.