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

• Published in: Journal of hazardous materials Vol. 444; p. 130397
• Main Authors: Qi, Xiaoli, Fu, Keyi, Yue, Mingyuan, Shou, Na, Yuan, Xuefeng, Chen, Xi, He, Chunyu, Yang, Yunfeng, Shi, Zunji
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.02.2023
• Subjects: Bacteria-algae interaction; Cadmium; Gene expression; Kynurenic acid; Metabolomics; Cadmium; Metabolomics; Kynurenic acid; Gene expression; Bacteria-algae interaction
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.130397

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+. [Display omitted] •Strain SH8 could interact with PCC6803 in strengthening Cd2+ toxicity resistance.•Kynurenic acid was the only metabolite that precipitated Cd2+ among 12 metabolites.•Kynurenic acid synthesis genes were increased when SH8 was added to PCC6803/Cd2+.