Measuring bacterial production via rate of incorporation of [3H]thymidine into DNA

Thymidine (TdR) incorporation into DNA as a measure of bacterial production in environmental samples relies on assumptions about what organisms incorporate exogenous thymidine, extent of dilution of labelled thymidine by internal and external pools, and analytical methods for recovery and purification of bacterial DNA. We have examined these assumptions with regard to the feasibility of using ³H]TdR incorporation in the water column and sediments of a blackwater river. The extent of dilution of added ³H]TdR may be determined with isotope dilution plots (Moriarty and Pollard, 1981 and 1982) and these indicate a wide range of degree of participation of added ³H]TdR. Previously described methods for extracting DNA from sediment bacteria may lead to underestimates and we described a more efficient recovery scheme.