Department of Zoology, University of Georgia, Athens, Georgia 30602, and College of Marine Studies, University of Delaware, Lewes, Delaware 19958.
Appl Environ Microbiol. 1986 Nov;52(5):992-1000. doi: 10.1128/aem.52.5.992-1000.1986.
The purpose of this study was to determine the depth distribution of bacterial biomass and production in a stratified lake and to test techniques to measure bacterial production in anaerobic waters. Bacterial abundance and incorporation of both [H]thymidine and [H]leucine into protein were highest in the metalimnion, at the depth at which oxygen first became unmeasurable. In contrast, [H]thymidine incorporation into DNA was highest in the epilimnion. The ratios of incorporation into DNA/protein averaged 2.2, 0.49, and 0.95 for the epilimnion, metalimnion, and hypolimnion, respectively. Low incorporation into DNA was not due to artifacts associated with the DNA isolation procedure. Recovery of added [H]DNA was about 90% in waters in which the portion of [H]thymidine incorporation into DNA was about 40%. At least some obligate anaerobic bacteria were capable of assimilating thymidine since aeration of anaerobic hypolimnion waters substantially inhibited thymidine incorporation. The depth profile of bacterial production estimated from total thymidine and leucine incorporation and the frequency of dividing cells were all similar, with maximal rates in the metalimnion. However, estimates of bacterial production based on frequency of dividing cells and leucine incorporation were usually significantly higher than estimates based on thymidine incorporation (using conversion factors from the literature), especially in anaerobic hypolimnion waters. These data indicate that the thymidine approach must be examined carefully if it is to be applied to aquatic systems with low oxygen concentrations. Our results also indicate that the interface between the aerobic epilimnion and anaerobic hypolimnion is the site of intense bacterial mineralization and biomass production which deserves further study.
本研究的目的是确定分层湖中的细菌生物量和生产力的深度分布，并测试在厌氧水中测量细菌生产力的技术。在氧首次无法测量的深度，即氧跃层，细菌丰度和[H]胸苷及[H]亮氨酸掺入蛋白质的量最高。相比之下，[H]胸苷掺入 DNA 的量在真光层最高。真光层、氧跃层和下光层的 DNA/蛋白质掺入比平均分别为 2.2、0.49 和 0.95。DNA 掺入量低不是由于与 DNA 分离过程相关的假象造成的。在[H]DNA 加入量约为 40%的水中，添加的[H]DNA 的回收率约为 90%。至少一些专性厌氧菌能够同化胸苷，因为对厌氧下光层水的曝气会大大抑制胸苷的掺入。根据总胸苷和亮氨酸掺入以及分裂细胞的频率估算的细菌生产力的深度分布均相似，最大速率出现在氧跃层。然而，基于分裂细胞频率和亮氨酸掺入估算的细菌生产力的估计值通常明显高于基于胸苷掺入的估计值（使用文献中的转化因子），尤其是在无氧下光层水中。这些数据表明，如果要将其应用于氧气浓度较低的水生系统，必须仔细检查胸苷方法。我们的结果还表明，好氧真光层和厌氧下光层之间的界面是强烈的细菌矿化和生物量产生的地点，值得进一步研究。
