Lin Yun-Chi, Kang Lee-Kuo, Shih Chi-Yu, Gong Gwo-Ching, Chang Jeng
Institute of Marine Biology, National Taiwan Ocean University, Keelung, 20224, Taiwan.
Institute of Marine Environment and Ecology, National Taiwan Ocean University, Keelung, 20224, Taiwan.
J Eukaryot Microbiol. 2018 Nov;65(6):792-803. doi: 10.1111/jeu.12521. Epub 2018 Apr 26.
Ribosomal RNA (rRNA) has been regarded as a proxy for metabolic activity and population growth in microbes, but the limitations and assumptions of this approach should be better defined, particularly in eukaryotic microalgae. In this study, the 18S rRNA/rDNA ratio of a marine diatom, Skeletonema tropicum, was examined in batch and semi-continuous cultures subjected to low nitrogen and phosphorus treatments at a temperature of 20 °C. In the semi-continuous cultures, the measured 18S rRNA/rDNA ratio ranged from 4.0 × 10 to 5.0 × 10 , and the logarithmic form of this ratio increased linearly with the population growth rate under both low nitrogen and low phosphorus conditions. In batch cultures grown under low nitrogen or low phosphorus conditions, log (rRNA/rDNA) also increased linearly with growth rate when the latter ranged between -0.4 and 1.5 day . The 18S rRNA/rDNA ratios of Skeletonema sampled from in the southern East China Sea were substantially lower than measured from laboratory cultures. Among the field samples, ratios obtained at a coastal station were higher than those obtained farther offshore. These results imply higher growth rate at the coastal station, but the influences of other factors, such as cell size and temperature, cannot be ruled out.
核糖体RNA（rRNA）一直被视为微生物代谢活性和种群增长的一个指标，但这种方法的局限性和假设应得到更明确的界定，尤其是在真核微藻中。在本研究中，对热带骨条藻（Skeletonema tropicum）这种海洋硅藻在20°C温度下进行低氮和低磷处理的分批培养和半连续培养中，检测了其18S rRNA/rDNA比值。在半连续培养中，测得的18S rRNA/rDNA比值范围为4.0×10至5.0×10，在低氮和低磷条件下，该比值的对数形式均随种群增长率呈线性增加。在低氮或低磷条件下生长的分批培养中，当生长速率在-0.4至1.5天之间时，log（rRNA/rDNA）也随生长速率呈线性增加。从中国东海南部采集的热带骨条藻的18S rRNA/rDNA比值显著低于实验室培养测得的值。在野外样本中，在沿海站点获得的比值高于离岸较远站点获得的比值。这些结果表明沿海站点的生长速率较高，但不能排除其他因素的影响，如细胞大小和温度。
