Guo Jiahua, Zhang Yibo, Mo Jiezhang, Sun Haotian, Li Qi
Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, College of Urban and Environmental Sciences, Northwest University, Xi'an, China.
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, China.
Front Microbiol. 2021 Jul 19;12:541451. doi: 10.3389/fmicb.2021.541451. eCollection 2021.
Occurrence of sulfonamide antibiotics has been reported in surface waters with the exposures ranging from < 1 ng L to approximately 11 μg L, which may exert adverse effects on non-target algal species, inhibiting algal growth and further hindering the delivery of several ecosystem services. Yet the molecular mechanisms of sulfonamide in algae remain undetermined. The aims of the present work are: (1) to test the hypothesis whether sulfamethoxazole (SMX) inhibits the folate biosynthesis in a model green alga ; and (2) to explore the effects of SMX at an environmentally relevant concentration on algal health. Here, transcriptomic analysis was applied to investigate the changes at the molecular levels in treated with SMX at the concentrations of 5 and 300 μg L. After 7-day exposure, the algal density in the 5 μg L group was not different from that in the controls, whereas a marked reduction of 63% in the high SMX group was identified. Using the adj < 0.05 and absolute log fold change > 1 as a cutoff, we identified 1 (0 up- and 1 downregulated) and 1,103 (696 up- and 407 downregulated) differentially expressed genes (DEGs) in the 5 and 300 μg L treatment groups, respectively. This result suggested that SMX at an environmentally relevant exposure may not damage algal health. In the 300 μg L group, DEGs were primarily enriched in the DNA replication and repair, photosynthesis, and translation pathways. Particularly, the downregulation of base and nucleotide excision repair pathways suggested that SMX may be genotoxic and cause DNA damage in alga. However, the folate biosynthesis pathway was not enriched, suggesting that 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 algal growth inhibition.
地表水中已报道有磺胺类抗生素存在，其暴露浓度范围从<1 ng/L到约11 μg/L，这可能对非目标藻类物种产生不利影响，抑制藻类生长，并进一步阻碍多种生态系统服务的提供。然而，磺胺类药物在藻类中的分子机制仍未确定。本研究的目的是：（1）检验磺胺甲恶唑（SMX）是否在模式绿藻中抑制叶酸生物合成的假设；（2）探索环境相关浓度的SMX对藻类健康的影响。在此，应用转录组分析来研究在5和300 μg/L浓度的SMX处理下藻类在分子水平上的变化。暴露7天后，5 μg/L组的藻类密度与对照组无差异，而高SMX组则显著降低了63%。以校正P<0.05和绝对对数倍变化>1为截断值，我们在5和300 μg/L处理组中分别鉴定出1个（0个上调和1个下调）和1103个（696个上调和407个下调）差异表达基因（DEG）。这一结果表明，环境相关暴露水平的SMX可能不会损害藻类健康。在300 μg/L组中，DEG主要富集在DNA复制与修复、光合作用和翻译途径中。特别是，碱基和核苷酸切除修复途径的下调表明SMX可能具有遗传毒性并导致藻类DNA损伤。然而，叶酸生物合成途径未富集，这表明SMX不一定通过其在细菌中的作用模式来抑制藻类生长。综上所述，本研究揭示了SMX抑制藻类生长的分子作用机制。
