Department of Ecology and Molecular Biology, Section of Microbiology, Royal Veterinary and Agricultural University, Rolighedsvej 21, DK-1958 Frederiksberg C., Denmark.
Appl Environ Microbiol. 1992 Nov;58(11):3647-53. doi: 10.1128/aem.58.11.3647-3653.1992.
Incorporation of leucine and valine into proteins of freshwater bacteria as a measure of bacterial production was tested in two eutrophic Danish lakes and was related to bacterial production measured by thymidine incorporation. In a depth profile (0 to 8 m) in Frederiksborg Castle Lake, incorporation of 100 nM leucine and valine gave similar rates of protein production. In terms of carbon, this production was about 50% lower than incorporation of 10 nM thymidine. In another depth profile in the same lake, incorporations of 10 nM valine and 100 nM leucine were identical, but differed from incorporations of 10 nM leucine and 100 nM valine. Bacterial carbon production calculated from incorporations of 10 nM thymidine and 10 nM leucine was similar, whereas 10 nM valine and 100 nM leucine and valine indicated an up to 2.4-fold-higher rate of carbon production. In a diel study in Lake Bagsvaerd, incorporation of 100 nM leucine and valine indicated a similar protein production, but the calculated carbon production was about 1.9-fold higher than the production based on uptake of 10 nM thymidine. Different diel changes in incorporation of the two amino acids and in incorporation of thymidine were observed. In both lakes, concentrations of naturally occurring leucine and valine were <5 nM in most samples. This means that the specific activity of a H isotope added at a concentration of 100 nM usually was diluted a maximum of 5%. Net assimilation of natural free amino acids in the lakes sustained 8 to 69% of the net bacterial carbon requirement, estimated from incorporation of leucine, valine, or thymidine. The present results indicate that incorporation of leucine and valine permits realistic measurements of bacterial production in freshwater environments.
在两个富营养化的丹麦湖泊中，测试了将亮氨酸和缬氨酸掺入淡水细菌蛋白质中作为细菌生产力的衡量标准，并将其与通过胸苷掺入测量的细菌生产力相关联。在弗雷德里克斯堡城堡湖的深度剖面（0 至 8 米）中，100 nM 亮氨酸和缬氨酸的掺入给出了相似的蛋白质产生速率。就碳而言，这种产生比掺入 10 nM 胸苷低约 50%。在同一湖中另一个深度剖面中，10 nM 缬氨酸和 100 nM 亮氨酸的掺入相同，但与 10 nM 亮氨酸和 100 nM 缬氨酸的掺入不同。从 10 nM 胸苷和 10 nM 亮氨酸的掺入中计算出的细菌碳产生相似，而 10 nM 缬氨酸和 100 nM 亮氨酸和缬氨酸则表明碳产生速率高达 2.4 倍。在 Bagsvaerd 湖的昼夜研究中，100 nM 亮氨酸和缬氨酸的掺入表明了相似的蛋白质产生，但计算出的碳产生比基于 10 nM 胸苷吸收的产生高约 1.9 倍。观察到两种氨基酸的掺入和胸苷的掺入有不同的昼夜变化。在两个湖泊中，大多数样本中天然亮氨酸和缬氨酸的浓度<5 nM。这意味着在浓度为 100 nM 添加的 H 同位素的比活度通常最多被稀释 5%。从亮氨酸、缬氨酸或胸苷的掺入中估计，湖泊中天然游离氨基酸的净同化作用维持了净细菌碳需求的 8%至 69%。目前的结果表明，亮氨酸和缬氨酸的掺入允许在淡水环境中对细菌生产力进行现实的测量。
