Department of Nature Conservation, Agricultural University, Ritzema Bosweg 32 a, 6703 AZ Wageningen, The Netherlands, and Freshwater Biological Laboratory, University of Copenhagen, Helsingørsgade 51, DK-3400 Hillerød, Denmark.
Appl Environ Microbiol. 1988 Sep;54(9):2213-9. doi: 10.1128/aem.54.9.2213-2219.1988.
The conversion factor for the calculation of bacterial production from rates of [H]thymidine incorporation was examined with diluted batch cultures of freshwater bacteria. Natural bacterial assemblages were grown in aged, normal, and enriched media at 10 to 20 degrees C. The generation time during 101 growth cycles covered a range from 4 to >200 h. The average conversion factor was 2.15 x 10 cells mol of thymidine incorporated into the trichloroacetic acid (TCA) precipitate (standard error = 0.29 x 10; n = 54), when the generation time exceeded 20 h. At generation times of <20 h, the average conversion factor was 11.8 x 10 cells mol of thymidine incorporated into TCA precipitate (standard error = 1.72 x 10; n = 47). The amount of radioactivity in purified DNA increased with decreasing generation time and increasing conversion factor (calculated from the TCA precipitate), corresponding to a decrease in the percentage in protein. The conversion factors calculated from purified DNA or from the TCA precipitate gave the same variability. Conversion factors did not change significantly with the medium, but were significantly higher at 20 degrees C than at 15 and 10 degrees C. A detailed examination of the [H]thymidine concentrations that were needed to achieve maximum labeling in DNA was carried out 6 times during a complete growth cycle. During periods with low generation times and high conversion factors, 15 nM [H]thymidine was enough for the maximum labeling of the TCA precipitate. This suggests that incorporation of [H]thymidine into DNA is probably limited by uptake during periods with generation times of <20 h and that freshwater bacterioplankton cell production sometimes is underestimated when a conversion factor of 2.15 x 10 cells mol of thymidine incorporated is used.
用稀释分批培养的淡水细菌来检验计算细菌生产力的[H]胸苷掺入率的转换因子。在 10 到 20°C 的老化、正常和富营养培养基中培养自然细菌组合。在 101 个生长循环中，代时的范围从 4 到>200 h。当代时超过 20 h 时，平均转换因子为 2.15×10 个细胞 mol 掺入三氯乙酸（TCA）沉淀中的胸苷（标准误差=0.29×10；n=54）。在代时<20 h 时，平均转换因子为 11.8×10 个细胞 mol 掺入 TCA 沉淀中的胸苷（标准误差=1.72×10；n=47）。随着代时的减少和转换因子的增加（根据 TCA 沉淀计算），纯化 DNA 中的放射性活性增加，对应于蛋白质百分比的减少。从 TCA 沉淀或从纯化 DNA 计算的转换因子具有相同的可变性。转换因子与培养基没有显著变化，但在 20°C 时明显高于 15 和 10°C。在一个完整的生长周期中，进行了 6 次详细检查需要达到 DNA 最大标记的[H]胸苷浓度。在代时低和转换因子高的时期，15 nM [H]胸苷足以使 TCA 沉淀达到最大标记。这表明，在代时<20 h 的时期，[H]胸苷掺入 DNA 可能受到摄取的限制，并且当使用 2.15×10 个细胞 mol 掺入的胸苷的转换因子时，淡水细菌浮游生物的细胞生产力有时会被低估。
