Repeated Exposure
Enhanced Toxicity of Clarithromycin
on Microcystis aeruginosa Versus Single
Exposure through Photosynthesis, Oxidative Stress, and Energy Metabolism
Shift
posted on 2024-02-23, 11:29authored byYufeng Mao, Kailai Ye, Shengfa Yang, Muhammad Salam, Weiwei Yu, Qiang He, Ruixu He, Hong Li
Antibiotics are being increasingly detected in aquatic
environments,
and their potential ecological risk is of great concern. However,
most antibiotic toxicity studies involve single-exposure experiments.
Herein, we studied the effects and mechanisms of repeated versus single
clarithromycin (CLA) exposure on Microcystis aeruginosa. The 96 h effective concentration of CLA was 13.37 μg/L upon
single exposure but it reduced to 6.90 μg/L upon repeated exposure.
Single-exposure CLA inhibited algal photosynthesis by disrupting energy
absorption, dissipation and trapping, reaction center activation,
and electron transport, thereby inducing oxidative stress and ultrastructural
damage. In addition, CLA upregulated glycolysis, pyruvate metabolism,
and the tricarboxylic acid cycle. Repeated exposure caused stronger
inhibition of algal growth via altering photosynthetic pigments, reaction
center subunits biosynthesis, and electron transport, thereby inducing
more substantial oxidative damage. Furthermore, repeated exposure
reduced carbohydrate utilization by blocking the pentose phosphate
pathway, consequently altering the characteristics of extracellular
polymeric substances and eventually impairing the defense mechanisms
of M. aeruginosa. Risk quotients calculated
from repeated exposure were higher than 1, indicating significant
ecological risks. This study elucidated the strong influence of repeated
antibiotic exposure on algae, providing new insight into antibiotic
risk assessment.