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

在水生生境的表面沃茨中，DOM的光解产生ROS和低分子量化合物。DOM光解对浮游细菌的活性和生长既有促进作用，也有抑制作用。然而，这些对比效应的相互作用还没有被调查方面的浮游细菌物种组成的影响。除了ROS产生（氧化应激）的直接负面影响外，细菌还通过ROS与化学矿化竞争低分子量DOM化合物。特别是，关于非常活泼的1O2的影响的信息很少。因此，我们将调查的代谢活动和物种组成的浮游细菌在腐殖酸丰富的湖泊相对于1O2暴露的变化。这种方法将有助于解开在何种程度上的直接影响（氧化应激）和间接影响（化学矿化的DOM）的1O2代影响浮游细菌物种的选择和生长动态。腐殖酸对生物体的毒性作用似乎与ROS，特别是1O2的产生有关。因此，丰富的浮游细菌物种分离以前将用于调查细菌防御机制对腐殖酸毒性和1O2在这个过程中的作用。

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.