colony forming unit CFU A titer measurement of viable bacterial or fungal numbers. Unlike in direct microscopic counts where all cells, dead and living, are counted, CFU measures viable cells. By convenience the results are given as CFU/mL (colony-forming units per milliliter) for water, and CFU/g (colony-forming units per gram) for soil or other porous material. data item Oliver He WEB: http://en.wikipedia.org/wiki/Colony-forming_unit titer