THIS INVENTION PROVIDES A BIOSENSOR BACTERIUM, EXACTLY SIMILAR TO A BACTERIUM THAT OCCURS NATURALLY IN POLLUTED ENVIRONMENTS AND THAT CONTAINS A GROUP OF GENES THAT ENCODES A REPORTER PROTEIN NOT FOUND IN THE NATURALLY OCCURRING BACTERIUM. IN ADDITION THIS INVENTION INCLUDES A METHOD FOR THE GENETICALLY MODIFIED BIOSENSOR AND ITS USE IN MEASURING A WIDE NUMBER OF CHEMICAL POLLUTANTS BY JUST EXPOSURING A SUSPENSION OF THE BIOSENSOR CELLS OBTAINED THROUGH THIS INVENTION TO THE WANTED TO MEASURE CHEMICAL MATERIAL. ACCORDING TO THE TOXICITY OF THIS MATERIAL THE BIOLUMINESCENT LIGHT PRODUCED BY THE CONSTRUCTED BIOSENSOR IS REDUCED. MOREOVER, THIS INVENTION INCLUDES THE ABILITY OF THE CONSTRUCTED BIOSENSOR TO SENSE TO THE TOXICITY OF PHENOLIC COMPOUNDS, HEAVY METALS, ORGANIC SOLVENTS, NITROGEN COMPOUNDS ANTIBIOTICS AND REAL WATER SAMPLES COLLECTED FROM DIFFERENT ECOSYSTEMS