In this review, we examine numerous applications of the green fluorescent protein (GFP) markeพ gene in environmental microbiology research. The (GFP) protein and its variants are reviewed and applications in plant-microbe interactions ,biofilms,biodegradation,bacterial-protozoan interactions, gene transfer, and biosensors are discussed. Methods for detecting green fluorescent protein-market cells are also examined. The (GFP) is a useful marker in environmental microorganisms ,allowing new research that will increase our understanding of microorganisms in the environmental.