AUTHOR=Guo Jiahua , Zhang Yibo , Mo Jiezhang , Sun Haotian , Li Qi 

TITLE=Sulfamethoxazole-Altered Transcriptomein Green Alga Raphidocelis subcapitata Suggests Inhibition of Translation and DNA Damage Repair

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.541451

DOI=10.3389/fmicb.2021.541451

ISSN=1664-302X

ABSTRACT=Occurrence of sulfonamide antibiotics has been reported in surface waters with the exposures ranging from ng L-1 to μg L-1, which may exert adverse effects on non-target algal species.. The aims of the present work are: 1) to test the hypothesis whether sulfamethoxazole (SMX) inhibits the folate biosynthesis in a model green alga Raphidocelis subcapitata; 2) to explore the effects of SMX at the environmentally relevant concentration on the algal health. Here, transcriptomic analysis was applied to investigate the changes at the molecular levels in R. subcapitata treated with SMX at the concentrations of 5 and 300 μg L−1. After 7 day exposure, the algal density in the 5 μg L−1 group was not different from that in controls, whereas a marked reduction of 63% in the high SMX group was identified. Using adj p < 0.05 and absolute log2 fold change > 1 as a cutoff, we identified 1 (0 up- and 1 down-regulated) and 1103 (696 up- and 407 down-regulated) differentially expressed genes (DEGs) in 5 and 300 μg L−1 treatment groups, respectively. This result suggested that SMX at the environmentally realistic exposure may not damage the algal health. In the 300 μg L−1 group, DEGs were primarily enriched in the DNA replication and repair, photosynthesis, and translation pathways. Particularly, the down-regulation of base and nucleotide excision repair pathways suggested that SMX may be genotoxic and cause DNA damage in alga. However, folate biosynthesis pathway was not enriched, suggesting SMX does not necessarily inhibit the algal growth via its mode of action in bacteria. Taken together, this study revealed the molecular mechanism of action of SMX in the algal growth inhibition.