ABSTRACT
The leucine (Leu) method for estimating bacterial production consists of measuring the incorporation of radiolabeled leucine into bacterial protein over time. The physiological basis of the leucine method is protein synthesis. Biomass production can be calculated from rates of protein synthesis because protein comprises a large, fairly constant fraction of bacterial biomass. It is possible to calculate biomass production without information about the cell sizes of bacterial assemblages. Leucine incorporation into protein is measured by following the appearance of radioactivity into material that is insoluble in hot trichloroacetic acid. Leu can be synthesized from other compounds, which leads to isotope dilution of the added radiolabeled Leu. The other potential problem with the Leu method is protein turnover. D. L. Kirchman et al. argued that it may be useful to measure protein turnover if organic matter is mineralized during protein turnover.
