How p-benzoquinone inhibits growth of various freshwater phototrophs: different susceptibility and modes of actions?

Interactions of polyphenols with freshwater phototrophs have been the focus of many studies, since polyphenols of various classes and their oxidation products (quinones) belong to natural organic matter in any freshwater body. Most of these studies were lacking information regarding the possible physiological modes of action. Therefore, we challenged eukaryotic and prokaryotic phototrophs by exposing them to p -benzoquinone (PBQ).Both groups of phototrophs showed clear stress responses which led to inhibition of growth and photosynthetic capacity. Two modes of action were elucidated for the short-term effects in the range of minutes to 24h: PBQ lowered the relative photosynthetic electron transport rate (rETR) and induced oxidative stress, in terms of lipid peroxidation. However, the inhibition of rETR by PBQ was only transient within minutes and was not detectable after 24 h, whereas growth inhibition continued until the end of culturing. Furthermore, it was shown that the effective concentration (EC) of PBQ to inhibit eukaryotic algal growth was much higher than the threshold for cyanobacterial growth inhibition. Microcystis aeruginosa was found to be the most susceptible species by far. Surprisingly, the latter cyanobacterial species did not show any inhibitory effect of PBQ on photosynthesis, indicating different physiological target sites governing inhibition of growth and photosynthetic electron transport independently. Permanent URL: http://hdl.handle.net/2047/d20002828