LEMAR (UMR6539), IUEM, Place Nicolas Copernic, 29280 Plouzané, France.
Res Microbiol. 2011 Nov;162(9):969-81. doi: 10.1016/j.resmic.2011.06.005. Epub 2011 Jun 13.
Diatoms of the genus Pseudo-nitzschia are potentially toxic microalgae, whose blooms can trigger amnesic shellfish poisoning. The purpose of this study was to test and adapt different probes and procedures in order to assess the physiological status of Pseudo-nitzschia multiseries at the cell level using flow cytometry. To perform these analyses, probes and procedures were first optimized for concentration and incubation time. The percentage of dead Pseudo-nitzschia cells, the metabolic activity of live cells and their intracellular lipid content were then measured following a complete growth cycle. In addition, chlorophyll autofluorescence and efficiency of photosynthesis (quantum yield) were monitored. The concentration and viability of bacteria present in the medium were also assessed. Domoic acid (DA) was quantified as well. Just before the exponential phase, cells exhibited high metabolic activity, but low DA content. DA content per cell became most abundant at the beginning of the exponential phase when lipid storage was high, which provided a metabolic energy source, and when they were surrounded by a high number of bacteria (high bacteria/P. multiseries ratio). These physiological measurements tended to decrease during exponential phase and until stationary phase, at which time P. multiseries cells did not contain any DA nor store any lipids, and started to die.
假交替单胞藻属的硅藻是潜在的有毒微藻，其大量繁殖会引发健忘性贝类中毒。本研究旨在测试和改进不同的探针和程序，以便使用流式细胞术在细胞水平上评估多列拟菱形藻的生理状态。为了进行这些分析，首先针对浓度和孵育时间对探针和程序进行了优化。然后，在完成整个生长周期后，测量了死拟菱形藻细胞的百分比、活细胞的代谢活性及其细胞内脂质含量。此外，还监测了叶绿素自发荧光和光合作用效率（量子产率）。还评估了培养基中存在的细菌的浓度和活力。同时还定量了软骨藻酸 (DA)。在指数生长期之前，细胞表现出高代谢活性，但 DA 含量低。当细胞内脂质储存量高、提供代谢能量来源时，并且当它们被大量细菌包围（高细菌/多列拟菱形藻比值）时，每个细胞中的 DA 含量变得最为丰富。这些生理测量值在指数生长期和静止期趋于下降，此时多列拟菱形藻细胞不再含有任何 DA 或储存任何脂质，并开始死亡。
