method and apparatus for the detection of microbes in liquids , in air and on non - living surfaces in which samples are exposed to electromagnetic radiation of specific energies capable of exciting various metabolites , cofactors and cellular and spore components , with the microbial cells to be sampled contained therein emit fluorescence that can be measured . the signal from the background and scattered excitation signals is removed from the fluorescence signals of the microbial components , the relative fluorescent signals of the intrinsic microbial components are required to lie within physiological ranges , and the amplitude of the background - corrected fluorescence signals used to enumerate the microbe content in the sample .