形成水华的物种wesenbergii和铜绿微囊藻在全球许多湖泊中都有,并可能在空间和时间上表现出交替的开花。随着环境变化的增加,蓝藻在越来越多的湖泊中绽放,通常以M.wesenbergii为主。铜绿假单胞菌对包括浮游动物在内的共存生物的不利影响已得到充分研究,而对韦森贝吉分枝杆菌的研究是有限的。为了比较这两个物种对浮游动物的影响,我们探索了来自不同菌株的产微囊藻毒素铜绿M.(Ma905和Ma526)和非产微囊藻毒素M.wesenbergii(Mw908和Mw929)的分泌物的影响,在慢性和急性暴露实验中,模型浮游动物大型蚤的繁殖。具体来说,我们测试了生理,生物化学,暴露于微囊藻分泌物的大麦草的分子和转录组特征。我们观察到,在所有治疗中,水蚤的体长,卵和后代数量都增加了。在测试的四种菌株中,Ma526增加了第一窝的大小,以及总卵和后代数量。微囊藻分泌物刺激诱导蜕皮激素的特定基因表达,少年激素,三酰甘油和卵黄蛋白原生物合成,which,反过来,提高了D.magna的卵和后代产量。即使微囊藻的所有菌株都会影响生长和繁殖,涉及许多基本途径的大量下调基因表明,Ma905菌株可能同时诱导D.magna的损伤。我们的研究强调了将韦森伯格菌纳入蓝藻水华生态风险评估的必要性,并强调,当评估仅基于微囊藻毒素的生产时,对浮游动物的后果可能并不明确。
The bloom-forming species Microcystis wesenbergii and M. aeruginosa occur in many lakes globally, and may exhibit alternating blooms both spatially and temporally. As environmental changes increase, cyanobacteria bloom in more and more lakes and are often dominated by M. wesenbergii. The adverse impact of M. aeruginosa on co-existing organisms including zooplanktonic species has been well-studied, whereas studies of M. wesenbergii are limited. To compare effects of these two species on zooplankton, we explored effects of exudates from different strains of microcystin-producing M. aeruginosa (Ma905 and Ma526) and non-microcystin-producing M. wesenbergii (Mw908 and Mw929), on reproduction by the model zooplankter Daphnia magna in both chronic and acute exposure experiments. Specifically, we tested physiological, biochemical, molecular and transcriptomic characteristics of D. magna exposed to Microcystis exudates. We observed that body length and egg and offspring number of the daphnid increased in all treatments. Among the four strains tested, Ma526 enhanced the size of the first brood, as well as total egg and offspring number. Microcystis exudates stimulated expression of specific genes that induced ecdysone, juvenile hormone, triacylglycerol and vitellogenin biosynthesis, which, in turn, enhanced egg and offspring production of D. magna. Even though all strains of Microcystis affected growth and reproduction, large numbers of downregulated genes involving many essential pathways indicated that the Ma905 strain might contemporaneously induce damage in D. magna. Our study highlights the necessity of including M. wesenbergii into the ecological risk evaluation of cyanobacteria blooms, and emphasizes that consequences to zooplankton may not be clear-cut when assessments are based upon production of microcystins alone.