Evaluation of the toxicity of clozapine on the freshwater diatom Navicula sp. using the FTIR spectroscopy

Integrated inactivation of Microcystis aeruginosa and degradation of microcystin-LR by direct current glow discharge plasma in liquid-phase: Mechanisms and cell deactivation process

The frequent occurrence of blooms of Microcystis aeruginosa (M. aeruginosa) and the subsequent release of microcystin-LR (MC-LR) in eutrophic waters pose a serious threat to aquatic ecosystems. This study investigated the optimal conditions for inactivating M. aeruginosa and the degrading MC-LR using direct current glow discharge plasma in liquid phase (DC-LGDP), analyzed the potential inactivation mechanisms and the cell deactivation process of M. aeruginosa. The results showed that DC-LGDP generated reactive species (i.e., •OH, 1O2, and H2O2), active Cl and electroporation effect collectively contributed to inactivation of M. aeruginosa and degradation of MC-LR. The 97.07 % inactivation efficiency of M. aeruginosa and 94.98 % degradation rate of MC-LR were achieved with higher energy yield and without generating nitrogen oxides. Meanwhile, DC-LGDP destroyed the cell integrity, eliminated their antioxidant capacity and reduced the content of photosynthetic pigments. The transcriptome analysis indicated that the transcripts of genes related to photosynthesis, ribosome biosynthesis, ABC transporters, and nitrogen metabolism pathway in M. aeruginosa were altered by DC-LGDP. This study provides insights into the inactivation of M. aeruginosa by DC-LGDP, while elucidating the potential inactivation mechanisms and the cell deactivation process involved. It may be important for the eco-friendly inactivation of M. aeruginosa blooms in natural water bodies.

Effects of four antibiotics on the photosynthetic light reactions in the green alga Chlorella pyrenoidosa

Antibiotics are ubiquitously present in aquatic environments, posing a serious ecological risk to aquatic ecosystems. However, the effects of antibiotics on the photosynthetic light reactions of freshwater algae and the underlying mechanisms are relatively less understood. In this study, the effects of 4 representative antibiotics (clarithromycin, enrofloxacin, tetracycline, and sulfamethazine) on a freshwater alga (Chlorella pyrenoidosa) and the associated mechanisms, primarily focusing on key regulators of the photosynthetic light reactions, were evaluated. Algae were exposed to different concentrations of clarithromycin (0.0-0.3 mg/L), enrofloxacin (0.0-30.0 mg/L), tetracycline (0.0-10.0 mg/L), and sulfamethazine (0.0-50.0 mg/L) for 7 days. The results showed that the 4 antibiotics inhibited the growth, the photosynthetic pigment contents, and the activity of antioxidant enzymes. In addition, exposure to clarithromycin caused a 118.4 % increase in malondialdehyde (MDA) levels at 0.3 mg/L. Furthermore, the transcripts of genes for the adenosine triphosphate (ATP) - dependent chloroplast proteases (ftsH and clpP), genes in photosystem II (psbA, psbB, and psbC), genes related to ATP synthase (atpA, atpB, and atpH), and petA (related to cytochrome b6/f complex) were altered by clarithromycin. This study contributes to a better understanding of the risk of antibiotics on primary producers in aquatic environment.