Weiling Sun's research group in the School of Environment revealed the effects of micro/nanoplastics and azithromycin on cyanobacterial photosynthetic carbon sequestration under single and composite pollution conditions

Plastic pollution and antibiotic pollution are pervasive in the global water environment, seriously threatening the health of
aquatic ecosystems.
Micro/nanoplastics and antibiotics widely coexist in the aqueous environment, resulting in compound toxic effects
on aquatic organisms.
Cyanobacteria are important primary producers of aquatic ecosystems and have an important regulatory effect
on global carbon and oxygen fluxes.
Therefore, it is of great ecological significance
to explore the composite toxic effects of microplastics/nanoplastics and antibiotics on cyanobacteria.

Based on this, Professor Sun Weiling's research group from the School of Environmental Science and Engineering of Peking University discussed the effects of polystyrene micro/nanoplastic (0.
05~50μm) and azithromycin on cyanobacteria Synechocystis sp.
Toxicity mechanism
of PCC 6803.
This work focuses on the effects of micro/nanoplastics and azithromycin on photosynthetic carbon sequestration in cyanobacteria, and reveals the toxicity mechanism
of single and composite contamination of microplastics/nanoplastics and azithromycin at different particle sizes from the protein level 。 The research results are based on "single and combined exposure to micro (nano) plastics and azithromycin disturbing the photosynthetic carbon fixation of Synechocystis sp.
" The title was published in Environmental Science-Nano and was selected as the cover article
.

Screenshot of the cover

This work found the antagonistic effect between micro/nanoplastics and azithromycin that decreases with the increase of plastic particle size, revealing that nanoplastics mainly adversely affect algal cells by damaging the integrity of cell membranes, while microplastics mainly affect the photosynthetic carbon
sequestration of algae through shading effect.
Microplastics showed a stronger inhibitory effect on cyanobacterial photosynthetic carbon sequestration than nanoplastics under single and azithromycin composite pollution conditions, mainly manifested in the decrease of photosynthetic efficiency and electron transport rate of algal cells, as well as the inactivation of carbonase, photosynthetic related proteins and carbon dioxide assimilation-related proteins down-regulation
.
Azithromycin is a high-risk pollutant (EC50=3.
9μg/L) for cyanobacteria, which has no obvious interference with the photosynthetic carbon sequestration of Synechocystis at EC20 concentration (1μg/L), but its coexistence with micro/nanoplastics further inhibits the photosynthetic
carbon sequestration of Synechocystis by micro/nanoplastics.

You Xiuqi, a 2020 doctoral student, is the first author of the article, and Sun Weiling is the corresponding author
.
This research work was supported
by the National Natural Science Foundation of China (51925901 and 51879001).