Paul J H, Jeffrey W H, Cannon J P
Department of Marine Science, University of South Florida, St. Petersburg 33701-5016.
Appl Environ Microbiol. 1990 Oct;56(10):2957-62. doi: 10.1128/aem.56.10.2957-2962.1990.
Production of dissolved macromolecules by ambient autotrophic and heterotrophic microbial populations was measured in a eutrophic Florida reservoir by in situ labeling with various radioactive substrates. When [3H]thymidine was used as the precursor, production of labeled dissolved DNA, RNA, and protein was observed. The rate of production of labeled dissolved macromolecules was 3.1% the rate of cellular incorporation of [3H]thymidine, and the production of dissolved DNA represented 2.3% the rate of cellular DNA incorporation. Microautotrophic populations labeled with NaH[14C]CO3 produced dissolved RNA and protein at rates of 0.24 and 0.11 micrograms of C/liter per h, respectively, or 1.8% the total rate of carbon fixation, with no measurable dissolved DNA production. In an attempt to specifically label phytoplankton DNA, samples were incubated with [3H]adenine or 32Pi in the presence and absence of the photosynthetic inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Although DCMU inhibited 14C fixation by approximately 99%, this antimetabolite had only a slight effect on [3H]adenine incorporation and no effect on 32P incorporation into cellular macromolecules. Significant amounts of dissolved DNA were produced in both [3H]adenine and 32Pi incubations, but again DCMU had no effect on the production rates. These results indicate that actively growing populations of both phytoplankton and bacterioplankton produced dissolved RNA and protein, while only active bacterioplankton produced measurable quantities of dissolved DNA. Dead or senescent phytoplankton may have produced dissolved DNA, but would not be measured in the relatively short incubations used. These findings also indicate that [3H]adenine and 32Pi primarily labeled heterotrophic bacterioplankton and not phytoplankton in this environment.
通过用各种放射性底物进行原位标记，在佛罗里达州一个富营养化水库中测定了自养和异养微生物群落产生溶解态大分子的情况。当使用[³H]胸腺嘧啶核苷作为前体时，观察到了标记的溶解态DNA、RNA和蛋白质的产生。标记的溶解态大分子的产生速率是[³H]胸腺嘧啶核苷细胞内掺入速率的3.1%，溶解态DNA的产生占细胞内DNA掺入速率的2.3%。用NaH[¹⁴C]CO₃标记的微型自养生物群落分别以每小时0.24和0.11微克碳/升的速率产生溶解态RNA和蛋白质，即占总碳固定速率的1.8%，未检测到溶解态DNA的产生。为了特异性标记浮游植物DNA，在有和没有光合抑制剂3-(3,4-二氯苯基)-1,1-二甲基脲（DCMU）的情况下，将样品与[³H]腺嘌呤或³²Pi一起孵育。尽管DCMU抑制了约99%的¹⁴C固定，但这种抗代谢物对[³H]腺嘌呤掺入的影响很小，对³²P掺入细胞大分子没有影响。在[³H]腺嘌呤和³²Pi孵育中都产生了大量的溶解态DNA，但DCMU对产生速率没有影响。这些结果表明，活跃生长的浮游植物和浮游细菌群落都产生溶解态RNA和蛋白质，而只有活跃的浮游细菌产生可测量量的溶解态DNA。死亡或衰老的浮游植物可能产生了溶解态DNA，但在所用的相对较短的孵育时间内无法检测到。这些发现还表明，在这种环境中，[³H]腺嘌呤和³²Pi主要标记异养浮游细菌而不是浮游植物。
