Faculty of Science and Engineering, Soka University, Tangi, Hachioji, Tokyo, Japan.
Center for Regional Environmental Research, National Institute for Environmental Studies, Onogawa, Tsukuba, Ibaraki, Japan.
PLoS One. 2020 Feb 27;15(2):e0229740. doi: 10.1371/journal.pone.0229740. eCollection 2020.
Bacterial production has been often estimated from DNA synthesis rates by using tritium-labeled thymidine. Some bacteria species cannot incorporate extracellular thymidine into their DNA, suggesting their biomass production might be overlooked when using the conventional method. In the present study, to evaluate appropriateness of deoxyribonucleosides for evaluating bacterial production of natural bacterial communities from the viewpoint of DNA synthesis, incorporation rates of four deoxyribonucleosides (thymidine, deoxyadenosine, deoxyguanosine and deoxycytidine) labeled by nitrogen stable isotope (15N) into bacterial DNA were examined in both ocean (Sagami Bay) and freshwater (Lake Kasumigaura) ecosystems in July 2015 and January 2016. In most stations in Sagami Bay and Lake Kasumigaura, we found that incorporation rates of deoxyguanosine were the highest among those of the four deoxyribonucleosides, and the incorporation rate of deoxyguanosine was approximately 2.5 times higher than that of thymidine. Whereas, incorporation rates of deoxyadenosine and deoxycytidine were 0.9 and 0.2 times higher than that of thymidine. These results clearly suggest that the numbers of bacterial species which can incorporate exogenous deoxyguanosine into their DNA are relatively greater as compared to the other deoxyribonucleosides, and measurement of bacterial production using deoxyguanosine more likely reflects larger numbers of bacterial species productions.
细菌的生产力通常通过使用氚标记的胸腺嘧啶来从 DNA 合成率进行估算。有些细菌物种无法将细胞外的胸腺嘧啶掺入其 DNA 中，这表明在使用传统方法时可能会忽略其生物量的产生。在本研究中，为了从 DNA 合成的角度评估脱氧核苷用于评估天然细菌群落中细菌生产力的适宜性，于 2015 年 7 月和 2016 年 1 月在海洋（相模湾）和淡水（霞浦湖）生态系统中检查了用氮稳定同位素（15N）标记的四种脱氧核苷（胸腺嘧啶、脱氧腺苷、脱氧鸟苷和脱氧胞苷）掺入细菌 DNA 的速率。在相模湾和霞浦湖的大多数站位，我们发现脱氧鸟苷的掺入率在这四种脱氧核苷中最高，脱氧鸟苷的掺入率约为胸腺嘧啶的 2.5 倍。而脱氧腺苷和脱氧胞苷的掺入率分别为胸腺嘧啶的 0.9 倍和 0.2 倍。这些结果清楚地表明，能够将外源脱氧鸟苷掺入其 DNA 的细菌种类的数量相对较高，而使用脱氧鸟苷测量细菌生产力更可能反映出更多种类的细菌的生产力。
