Bacterial bioassay of microgram to subnanogram quantities of glucose

A simple and highly sensitive bioassay for the measurement of glucose is described. The method is based on the fact that the yields of cultured bacteria depend on the amount of glucose input, which is a limiting factor in Davis minimal medium. The number of cells cultured under fixed conditions was shown to be dependent on the amount of glucose in the culture medium. Therefore, the concentration of glucose can be measured by counting the cell number after culturing the bacteria. With Davis medium depleted of sodium citrate, we used this method to detect a subnanogram level of glucose, although with the accuracy of order of magnitude estimation. In the microgram per milliliter range of glucose, the cell number can be measured optically, with proliferation being proportional to the input glucose. The high selectivity for glucose of this method is based on the preferential usage of glucose as a carbon and energy source by the bacteria adopted. The feasibility of applying this method to other substances is discussed.