Effects of levofloxacin hydrochlordie on photosystem II activity and heterogeneity of Synechocystis sp.

Effects of LH on photosynthesis of Synechocystis sp. were investigated by a variety of in vivo chlorophyll fluorescence. O2 evolution and the photosystem II (PSII) activity were clearly inhibited by LH. Exposure to LH increased the proportion of PSIIβ and this weakened the connectivity between PSII units and hindered excitation energy-transfer between PSII units. LH decreased the density of the active photosynthetic reaction centers, inhibited electron transport, and increased the dissipated energy flux per reaction center. The inhibitory effect of LH on QA- reoxidation process could be divided into several stages. LH first inhibited the electron transfer from QA- to QB by weakening the connectivity between QA- and QB, and PQ binding began taking part in QA- reoxidation. At the second stage, the connectivity between QA- and PQ pool was broken and inhibition on PQ binding occurred. At this stage, some QA- began to be oxidized by S2(QAQB)−. Finally, when the connectivity between QA- and QB and PQ was completely broken, all QA- was oxidized through charge recombination.