APPLICATIONS FOR GREEN FLUORESCENT PROTEIN (GFP) IN THE STUDY OF HOST-PATHOGEN INTERACTIONS

The green fluorescent protein (GFP) from Aequorea victor ia is a novel fluorescent marker that has potential use in the study of bacterial p athogenicity, To explore some of the potential applications of GFP to the study of host-parasite interactions, we constructed two GFP expres sion vectors suitable for different facultative intracellular bacteria l pathogens, The first expression vector was tested in the enteric pat hogens, Salmonella typhimurium and Yersinia pseudotuberculosis, and th e second vector tested in Mycobacterium marinum (Mm). Both expression vectors were found to be stable and to direct high levels of GFP synth esis. Standard epifluorescence microscopy was used to detect all three bacterial pathogenic species during the early and late stages of infe ction of live mammalian cells, Mm expressing gfp was also visualized i n infected animal tissues, gfp expression did not adversely affect bac terial survival, nor did it compromise entry into mammalian cells or t heir survival within macrophages. In addition, all three gfp-expressin g bacterial pathogens could be detected and sorted in a flow cytometer , either alone or in association with epithelial cells or macrophages. Therefore, GFP not only provides a convenient tool to image pathogeni c bacteria, but allows the quantitative measurement of bacterial assoc iation with mammalian cells.