The role of singlet oxygen and humic acid toxicity for bacterioplankton activity and community structure

在水生生境的地表水中，活性氧和低分子量化合物是由DOM光解产生的。DOM光解对浮游细菌的活性和生长均有刺激和抑制作用。然而，这些对比效应的相互作用尚未研究它们对浮游细菌种类组成的影响。除了ROS生成（氧化应激）的直接负面影响外，细菌还与ROS的化学矿化竞争低分子量DOM化合物。特别是，关于极具活性的o2的影响的信息很少。因此，我们将研究富腐植酸湖泊中浮游细菌的代谢活性和种类组成与1O2暴露变化的关系。这种方法将有助于揭示1O2产生的直接影响（氧化应激）和间接影响（DOM的化学矿化）在多大程度上影响浮游细菌物种的选择和生长动力学。腐植酸对生物体的毒性作用似乎与活性氧，特别是氧的产生有关。因此，将利用之前分离到的丰富的浮游细菌种类来研究细菌对腐植酸毒性的防御机制以及1O2在这一过程中的作用。

In surface waters of aquatic habitats ROS and low molecular weight compounds are generated by the photolysis of DOM. Both, stimulating and inhibitory effects of DOM photolysis on bacterioplankton activity and growth have been observed. However, the interaction of those contrasting effects has not been investigated with respect to their influence on bacterioplankton species composition. Beside the direct negative effects of ROS generation (oxidative stress), bacteria compete with chemical mineralization by ROS for low molecular weight DOM compounds. In particular, information on the effects of the very reactive 1O2 is scarce. Therefore, we will investigate the metabolic activity and species composition of bacterioplankton in a humic acid rich lake with respect to changes in 1O2 exposure. This approach will help to unravel to which extent direct effects (oxidative stress) and indirect effects (chemical mineralization of DOM) of 1O2 generation influence selection and growth dynamics of bacterioplankton species. Toxic effects of humic acids on organisms appear to be correlated to ROS and in particular 1O2 generation. Hence, abundant bacterioplankton species isolated previously will be used to investigate bacterial defense mechanisms against humic acid toxicity and the role of 1O2 in this process.