Fluorescence in situ hybridization (FISH) for direct visualization of microorganisms.

As a technique allowing simultaneous visualization, identification, enumeration and localization of individual microbial cells, fluorescence in situ hybridization (FISH) is useful for many applications in all fields of microbiology. FISH not only allows the detection of culturable microorganisms, but also of yet-to-be cultured (so-called unculturable) organisms, and can therefore help in understanding complex microbial communities. In this review, methodological aspects, as well as problems and pitfalls of FISH are discussed in an examination of past, present and future applications.