Kynurenic acid mediates bacteria-algae consortium in resisting environmental cadmium toxicity

Xiaoli Qi; Keyi Fu; Mingyuan Yue; Na Shou; Xuefeng Yuan; Xi Chen; Chunyu He; Yunfeng Yang; Zunji Shi

doi:10.1016/j.jhazmat.2022.130397

Kynurenic acid mediates bacteria-algae consortium in resisting environmental cadmium toxicity

J Hazard Mater. 2023 Feb 15;444(Pt A):130397. doi: 10.1016/j.jhazmat.2022.130397. Epub 2022 Nov 14.

Authors

Xiaoli Qi¹, Keyi Fu², Mingyuan Yue², Na Shou², Xuefeng Yuan², Xi Chen², Chunyu He², Yunfeng Yang³, Zunji Shi⁴

Affiliations

¹ State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, Center for Grassland Microbiome, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China; National Key Laboratory of Crop Genetic Improvement, MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, Hubei, China.
² State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, Center for Grassland Microbiome, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China.
³ State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: yangyf@tsinghua.edu.cn.
⁴ State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, Center for Grassland Microbiome, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730000, China. Electronic address: shizj@lzu.edu.cn.

PMID: 36403444
DOI: 10.1016/j.jhazmat.2022.130397

Abstract

Cadmium (Cd²⁺) is a toxic heavy metal in the environment, posing severe damage to animal health and drinking water safety. The bacteria-algae consortium remediates environmental Cd²⁺ pollution by secreting chelating reagents, but the molecular mechanisms remain elusive. Here, we showed that Cellulosimicrobium sp. SH8 isolated from a Cd²⁺-polluted lake could interact with Synechocystis sp. PCC6803, a model species of cyanobacteria, in strengthening Cd²⁺ toxicity resistance, while SH8 or PCC6803 alone barely immobilized Cd²⁺. In addition, the SH8-PCC6803 consortium, but not SH8 alone, could grow in a carbon-free medium, suggesting that autotrophic PCC6803 enabled the growth of heterotrophic SH8. Totally, 12 metabolites were significantly changed when SH8 was added to PCC6803 culture in the presence of Cd²⁺ (PCC6803/Cd²⁺). Among them, kynurenic acid was the only metabolite that precipitated Cd²⁺. Remarkably, adding kynurenic acid increased the growth of PCC6803/Cd²⁺ by 14.1 times. Consistently, the expressions of kynA, kynB, and kynT genes, known to be essential for kynurenic acid synthesis, were considerably increased when SH8 was added to PCC6803/Cd²⁺. Collectively, kynurenic acid secreted by SH8 mitigates Cd²⁺ toxicity for algae, and algae provide organic carbon for the growth of SH8, unveiling a critical link that mediates beneficial bacteria-algae interaction to resist Cd²⁺.

Keywords: Bacteria-algae interaction; Cadmium; Gene expression; Kynurenic acid; Metabolomics.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Actinomycetales*
Animals
Bacteria
Cadmium / toxicity
Cadmium Poisoning*
Kynurenic Acid

Substances

Cadmium
Kynurenic Acid