Effects of 4-tert-butylpyrocatechol and tea polyphenol on growth, physiology and antioxidant responses in Microcystis aeruginosa

Abstract

Global warming has increased the frequency of Microcystis aeruginosa blooms, leading to the deterioration of water quality and loss of biodiversity. Therefore, developing effective strategies for controlling M. aeruginosa blooms has become an important research topic. Plant extracts, 4‑tert-butylpyrocatechol (TBC) and tea polyphenol (TP) are commonly used for water purification and to increase fish immunity, which have great potential to inhibit cyanobacterial blooms. The inhibitory effects of TBC and TP on M. aeruginosa were investigated in terms of growth characteristics, cell membrane morphology, physiological, photosynthetic activities, and antioxidant enzymes activities. The results showed that TBC and TP inhibited the growth of M. aeruginosa by decreasing the chlorophyll fluorescence transients or increasing the antioxidant enzymes activities of M. aeruginosa. TBC damaged the cell morphology of M. aeruginosa, reduced extracellular polysaccharides and protein contents, and up-regulated the antioxidant activity-related gene (sod and gsh) expressions of M. aeruginosa. TP significantly decreased the photosynthetic pigment content, influenced the phycobiliprotein content, and strongly down-regulated the photosynthesis-related gene (psbA, psaB, and rbcL) relative expressions of M. aeruginosa. TBC caused significant oxidative stress, dysfunction of physiological metabolic processes, and damaged crucial biomacromolecules (e.g., lipids, proteins and polysaccharides), prompted the loss of cell integrity, ultimately leading to the death of M. aeruginosa. However, TP depressed photosynthetic activities and consequently inhibited the transfer of electrons, affected the electron transfer chain, decreased the photosynthetic efficiency, and eventually caused the death of M. aeruginosa cells. Our study showed the inhibitory effects and algicidal mechanisms of TBC and TP on M. aeruginosa, and provide a theoretical basis for restrain the overgrowth of M. aeruginosa.

Keywords: 4‑tert-butylpyrocatechol; Algicidal mechanism; Gene expression; Microcystis aeruginosa; Tea polyphenol.