Luciferase from E. coli is widely used in bioluminescent reporter assays to monitor gene expression and promoter activity in real time. It enables detection of biological processes such as bacterial infection, cellular metabolism, and environmental toxin responses without the need for external light sources, reducing background noise and improving sensitivity. This enzyme is particularly valuable in live-cell imaging and high-throughput screening due to its rapid, quantifiable light output. It is also employed in biosensors for detecting ATP, serving as a marker for microbial contamination in food safety, pharmaceuticals, and hygiene monitoring. Its application in molecular biology research supports the study of regulatory elements, signal transduction pathways, and pathogen-host interactions with high specificity and low toxicity.