Beisser Daniela, Kaschani Farnusch, Graupner Nadine, Grossmann Lars, Jensen Manfred, Ninck Sabrina, Schulz Florian, Rahmann Sven, Boenigk Jens, Kaiser Markus
Genome Informatics, Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, 45147 Essen, Germany.
Biodiversity, Faculty of Biology, University of Duisburg-Essen, Universitätsstr. 5, 45141 Essen, Germany.
PLoS One. 2017 Jan 5;12(1):e0168183. doi: 10.1371/journal.pone.0168183. eCollection 2017.
Aquatic environments are heavily impacted by human activities including climate warming and the introduction of xenobiotics. Due to the application of silver nanoparticles as bactericidal agent the introduction of silver into the environment strongly has increased during the past years. Silver ions affect the primary metabolism of algae, in particular photosynthesis. Mixotrophic algae are an interesting test case as they do not exclusively rely on photosynthesis which may attenuate the harmful effect of silver. In order to study the effect of silver ions on mixotrophs, cultures of the chrysophyte Poterioochromonas malhamensis were treated in a replicate design in light and darkness with silver nitrate at a sub-lethal concentration. At five time points samples were taken for the identification and quantitation of proteins by mass spectrometry. In our analysis, relative quantitative protein mass spectrometry has shown to be a useful tool for functional analyses in conjunction with transcriptome reference sequences. A total of 3,952 proteins in 63 samples were identified and quantified, mapping to 4,829 transcripts of the sequenced and assembled transcriptome. Among them, 720 and 104 proteins performing various cellular functions were differentially expressed after eight days in light versus darkness and after three days of silver treatment, respectively. Specifically pathways of the energy and primary carbon metabolism were differentially affected by light and the utilization of expensive reactions hints to an energy surplus of P. malhamensis under light conditions. The excess energy is not invested in growth, but in the synthesis of storage metabolites. The effects of silver were less explicit, observable especially in the dark treatments where the light effect could not mask coinciding but weaker effects of silver. Photosynthesis, particularly the light harvesting complexes, and several sulphur containing enzymes were affected presumably due to a direct interference with the silver ions, mainly affecting energy supply.
水生环境受到包括气候变暖及引入外源性生物物质在内的人类活动的严重影响。由于银纳米颗粒作为杀菌剂的应用，过去几年中银向环境中的引入量大幅增加。银离子会影响藻类的初级代谢，尤其是光合作用。兼养型藻类是一个有趣的测试对象，因为它们并非完全依赖光合作用，这可能会减弱银的有害影响。为了研究银离子对兼养型生物的影响，对金藻马勒姆波氏藻（Poterioochromonas malhamensis）的培养物进行了重复设计处理，在光照和黑暗条件下用亚致死浓度的硝酸银处理。在五个时间点取样，通过质谱法对蛋白质进行鉴定和定量。在我们的分析中，相对定量蛋白质质谱已被证明是结合转录组参考序列进行功能分析的有用工具。在63个样本中总共鉴定和定量了3952种蛋白质，这些蛋白质对应于已测序和组装转录组的4829个转录本。其中，分别在光照与黑暗条件下培养八天后以及银处理三天后，有720种和104种执行各种细胞功能的蛋白质差异表达。具体而言，能量和初级碳代谢途径受光照的影响不同，利用昂贵反应表明马勒姆波氏藻在光照条件下能量过剩。过剩的能量并非用于生长，而是用于储存代谢物的合成。银的影响不太明显，尤其是在黑暗处理中可以观察到，因为光照的影响无法掩盖银同时存在但较弱的影响。光合作用，特别是光捕获复合物，以及几种含硫酶受到影响，可能是由于与银离子的直接相互作用，主要影响了能量供应。
