Harnessing microbial resource Rhodopseudomonas palustris for saline-alkaline paddy soil amelioration: key role of...

Bioremediation offers an eco-friendly solution for soil salinization, yet few salt-alkali-tolerant microorganisms can adapt to redox fluctuations induced by wet-dry alternation in paddy soil. Rhodopseudomonas palustris (R. palustris) holds promise for addressing this challenge, while the mechanism is still poorly understood. This study established a microcosm experiment mimicking paddy wet-dry alternation by regulating redox conditions to investigate the mechanisms of R. palustris and its extracellular polymeric substances (EPS) in soil amelioration. R. palustris adapted well to redox alternation and significantly reduced soil pH and electrical conductivity (EC) by 3-7% and 7-28%. In anaerobic phase, R. palustris secreted organic acids and promoted EPS synthesis, which directly complexed salt ions and drove soil acidification. Upon transition to aerobic conditions, it accumulated glycogen and polyhydroxyalkanoate (PHA) to sustain growth and EPS secretion. In the subsequent aerobic phase, EPS gradually transformed into amino acids, fulvic acid, and humic-like substances, as revealed by excitation-emission matrix (EEM) spectra, thereby improving soil fertility. Metagenomic analysis further revealed R. palustris and its EPS reshaped the microbial community and regulated the expression of related functional genes. Collectively, this study demonstrates R. palustris serves as an effective microbial resource for sodic-saline paddy soil amelioration, with EPS acting as a key bioactive component that drives this process toward biotechnology-driven remediation strategies.