Dittami Simon M, Edvardsen Bente
Marine Biology, Department of Biology, University of Oslo, P.O. Box 1066 Blindern, 0316 Oslo, Norway.
J Phycol. 2012 Aug;48(4):1050-5. doi: 10.1111/j.1529-8817.2012.01183.x. Epub 2012 May 23.
Cell counts are the standard measure to quantify harmful algae and the basis for decisions on measures necessary to protect human health. Molecular detection methods have been developed for a range of algal species and genera, but these methods generally quantify DNA or RNA, and corresponding cell numbers are inferred based on the assumption that the cellular nucleic acid content is constant over time and in different conditions. Here, we tested this assumption for ichthyotoxic flagellates of the genus Pseudochattonella (Dictyochophyceae) under different light, temperature, salinity, and nutrient conditions. Our results show changes in cellular RNA contents of nearly one order of magnitude depending on the condition and also the time of exposure, rendering it difficult to anticipate per-cell RNA yields even if environmental conditions are known. However, cellular RNA content was positively correlated with cell size and growth rate across our experiments, and total RNA was comparable to cell number as a predictor for total biovolume. These results demonstrate the importance of considering the variability of RNA levels for comparisons with cell counts and provide a valuable aid for the interpretation of data from RNA-based detection methods.
细胞计数是量化有害藻类的标准方法，也是决定保护人类健康所需措施的依据。针对一系列藻类物种和属开发了分子检测方法，但这些方法通常是对DNA或RNA进行量化，相应的细胞数量是基于细胞核酸含量在不同时间和条件下恒定的假设推断出来的。在此，我们在不同的光照、温度、盐度和营养条件下，对拟凯伦藻属（网鞭藻纲）的鱼类毒性鞭毛虫进行了这一假设的测试。我们的结果表明，根据条件和暴露时间的不同，细胞RNA含量会发生近一个数量级的变化，即使已知环境条件，也难以预测每细胞的RNA产量。然而，在我们的实验中，细胞RNA含量与细胞大小和生长速率呈正相关，总RNA与细胞数量作为总生物量的预测指标相当。这些结果证明了在与细胞计数进行比较时考虑RNA水平变异性的重要性，并为基于RNA的检测方法的数据解释提供了有价值的帮助。
