ABSTRACT
Measurement of the rate of incorporation of tritiated thymidine into bacterial deoxyribonucleic acid (DNA) has become the mostly commonly used method for measuring bacterial production in both water column and sediments. The basic rationale for the technique is that DNA synthesis is tightly coupled to cell division and that most bacteria actually incorporate exogenous thymidine (TdR) into newly synthesized DNA. Advantages of the method include: fairly short-term incubations yielding instantaneous rates of production; high sensitivity in the sense that even slow turnover times yield measurable rates of TdR incorporation; and relatively simple sample incubation and preparation techniques. In sediments, practically all workers find significant dilution of added TdR unless very large amounts of TdR are added to the sediment. Isotope dilution is determined by incubating samples with different specific activities of labeled TdR.
