Bacterial soluble secondary metabolites enhance algal tolerance to pyridine in an indirect-contact symbiotic system

Xinying Hou; Xiaoyu Zhang; Yan Li; Muyu Li; Xinbai Jiang; Jinyou Shen; Dan Chen

doi:10.1016/j.biortech.2025.132890

Bacterial soluble secondary metabolites enhance algal tolerance to pyridine in an indirect-contact symbiotic system

Bioresour Technol. 2025 Jun 25:132890. doi: 10.1016/j.biortech.2025.132890. Online ahead of print.

Authors

Xinying Hou¹, Xiaoyu Zhang¹, Yan Li¹, Muyu Li¹, Xinbai Jiang¹, Jinyou Shen², Dan Chen³

Affiliations

¹ Key Laboratory of Environmental Remediation and Ecological Health, Ministry of Industry and Information Technology, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; Engineering Research Centre of Chemical Pollution Control, Ministry of Education, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
² Key Laboratory of Environmental Remediation and Ecological Health, Ministry of Industry and Information Technology, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; Engineering Research Centre of Chemical Pollution Control, Ministry of Education, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; Key Laboratory of Jiangxi Province for Persistent Pollutants Prevention Control and Resource Reuse, Nanchang Hangkong University, Nanchang 330063, China.
³ Key Laboratory of Environmental Remediation and Ecological Health, Ministry of Industry and Information Technology, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China; Engineering Research Centre of Chemical Pollution Control, Ministry of Education, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China. Electronic address: danchen@njust.edu.cn.

PMID: 40578701
DOI: 10.1016/j.biortech.2025.132890

Abstract

Bacterial soluble secondary metabolites are key regulators of interspecies interactions in algae-bacteria symbiotic systems (ABSS), but their in situ roles under toxic environmental conditions remain poorly understood. This study employed an indirect-contact system to investigate their contribution to the tolerance of Chlorella sorokiniana under pyridine stress. Bacterial degradation reduced pyridine concentrations by 23.1 % and generated 5.24 mg L^-1 of NH₄⁺-N, alleviating algal oxidative stress. Diffusible bacterial secondary metabolites, including N-acyl homoserine lactones (1.2-fold increased), indole-3-acetic acid (1.1-fold increased), and humic-like substances, accumulated in the algal compartment. These metabolites activated algal antioxidant defenses, promoted photosystem repair, and supported algal growth. Compared with monoculture, algal biomass increased by 2.2-fold, and carbohydrate content rose by 21.9 %, alongside the activation of SOD-glutathione detoxification pathways. Transcriptomic analysis revealed significant upregulation of genes related to photosynthesis, DNA repair, and protein refolding. These findings uncover an indirect-contact regulatory mechanism that enhances algal resilience. They also support a modular strategy that combines functional bacterial consortia with spatially structured systems to improve ABSS performance in treating nitrogen-containing heterocyclic pollutants.

Keywords: Algae-bacteria symbiotic system (ABSS); Bacterial soluble secondary metabolites; Indirect-contact; Pyridine.