The Immunofluorescence Approach in Microbial Ecology

Fluorescent markers appropriately conjugated to antibody proteins provide the basis for a method to visualize those antibodies as they participate in antigenantibody reactions. The method is referred to as the fluorescent antibody (FA) or immunofluorescence (IF) technique; it has been in widespread and successful use in medical microbiology and in pathology as a highly sensitive and specific cytochemical staining procedure for many years. Most current applications of the technique are for the localization of cellular and viral antigens in tissues and for the rapid detection and identification of infectious agents. The same features of the FA technique that make possible the detection and identification of microbial pathogens in animal tissues provide its potential for autecological application in microbial ecology. Autecology, as an approach whereby the individual microorganism is studied directly in its natural environment, has been virtually unavailable to microbial ecology because of technical difficulties imposed by the small size and nondescript morphology of microorganisms and by the physical complexities of the natural environment. Direct microscopic examination of the natural environment could become a powerful tool for autecological study if a method were available to recognize one specific microorganism among all others present in the field of view. Such a capability is inherent in the FA technique. Because extremely small amounts of fluorochrome-marked antibody may be detected against a dark background by fluo