Different sensitivity of selected planktonic eukaryotic and prokaryotic phototrophs to dissolved humic substances: potential modes of action and ecological implications

在淡水生态系统中，腐殖物质（HS）包括大部分的有机碳，并采取了部分由许多，但显然不是所有的淡水光养生物。内化HS导致氧化应激和/或直接在光合电子链内相互作用。在这方面，原核生物似乎比真核生物更敏感。为了阐明潜在的潜在作用模式，应研究暴露于HS后选定的球菌绿色藻类和蓝藻的HS吸收/净化、生长速率和光合性能。采用罗丹明B试验检查摄取和净化0.5 kDa分子的一般能力。为了测试HS中的醌型结构单元是减少光合氧释放的有效结构的假设，将制备和应用具有增强的氧化还原性质的一种不同的富含醌型或苯酚的HS。作为氧化应激参数，将测定H2 O2、TOSC、抗氧化酶活性和底物含量以及某些应激基因的表达。生长速率和光合活性将与氧化应激状态有关。多重胁迫胁迫耐受性的潜在获得将通过预先暴露于HS的光养生物的耐盐性来测试。为了评估内化HS与光合电子传递的作用模式，将应用不同的荧光和光学技术来识别推定的靶点。

In freshwaters ecosystems, humic substances (HS) comprise the majority of organic carbon and are taken up in parts by many, but obviously not all freshwater phototrophs. Internalized HS lead to oxidative stress and/or interact directly within the photosynthetic electron chain. In this regard, prokaryotes appear to be more sensitive than eukaryotes. To elucidate potential underlying modes of action, uptake/depuration of HS, growth rates, and photosynthetic performance of selected coccal green algae and cyanobacteria shall be studied upon exposure to HS. The general ability to uptake and depurate molecules of 0.5 kDa will be checked with the rhodamine B assay. To test the assumption that quinoid building blocks in the HS are the effective structures for the reduction of photosynthetic oxygen release, one differently quinoid- or phenol-enriched HS with enhanced redox properties will be prepared and applied. As oxidative stress parameters, H2O2, TOSC, activity of antioxidant enzymes and substrate contents as well as the expression of certain stress genes will be determined. Growth rates and photosynthetic activity will be related to the oxidative stress status. The potential acquisition of a multiple stress stress tolerance will be tested by solt-tolerance of phototrophs pre-exposed to HS. To assess the mode of action of internalized HS with the photosynthetic electron transport, different fluorescence and optical techniques will be applied to identify the putative targets.