Univ Rennes, CNRS, ECOBIO-UMR 6553, F-35000 Rennes, France.
School of Pharmacy and Life Sciences, Robert Gordon University, Aberdeen AB10 7GJ, UK.
Toxins (Basel). 2019 Jul 19;11(7):421. doi: 10.3390/toxins11070421.
While the intracellular function of many toxic and bioactive cyanobacterial metabolites is not yet known, microcystins have been suggested to have a protective role in the cyanobacterial metabolism, giving advantage to toxic over nontoxic strains under stress conditions. The zooplankton grazer reduce cyanobacterial dominance until a certain density, which may be supported by exudates, affecting the cyanobacterial physiological state and metabolites' production. Therefore, we hypothesized that spent medium will impact the production of cyanobacterial bioactive metabolites and affect cyanobacterial photosynthetic activity in the nontoxic, but not the toxic strain. Microcystin (MC-LR and des-MC-LR) producing PCC7806 and its non-microcystin producing mutant were exposed to spent media of different densities and culture durations. spent medium of the highest density (200/L) cultivated for the shortest time (24 h) provoked the strongest effect. spent medium negatively impacted the photosynthetic activity of PCC7806, as well as the dynamics of intracellular and extracellular cyanobacterial metabolites, while its mutant was unaffected. In the presence of medium, microcystin does not appear to have a protective role for the strain. On the contrary, extracellular cyanopeptolin A increased in PCC7806 although the potential anti-grazing role of this compound would require further studies.
虽然许多有毒和生物活性蓝藻代谢物的细胞内功能尚不清楚，但微囊藻毒素被认为在蓝藻代谢中具有保护作用，使有毒菌株在胁迫条件下比非毒性菌株具有优势。浮游动物摄食者减少了蓝藻的优势度，直到达到一定的密度，这可能是由分泌物支持的，影响蓝藻的生理状态和代谢产物的产生。因此，我们假设，使用过的培养基将影响蓝藻生物活性代谢产物的产生，并影响无毒但非毒性菌株的蓝藻光合作用活性。暴露于不同密度和培养时间的用过的培养基中，产微囊藻毒素（MC-LR 和去甲 MC-LR）的 PCC7806 及其非产微囊藻毒素突变体。培养时间最短（24 小时）、密度最高（200/L）的用过的培养基引起的影响最强。用过的培养基对 PCC7806 的光合作用活性以及细胞内和细胞外蓝藻代谢物的动态产生了负面影响，而其突变体则不受影响。在培养基存在的情况下，微囊藻毒素似乎对该菌株没有保护作用。相反，胞外蓝藻肽 A 在 PCC7806 中增加，尽管这种化合物的潜在抗食草作用需要进一步研究。
