Root surface microbial biofilms in phytoremediation: Formation processes, regulatory mechanisms, influencing factors and roles

Abstract

Root surface microbial biofilm (RSMB), formed by microorganisms colonizing plant root surfaces, constitutes the critical interface between soil environment and root system during phytoremediation. However, the mechanisms underlying RSMB formation and its roles in phytoremediation have not been comprehensively reviewed. This review integrates knowledge from microbial ecology, environmental science, and plant physiology to critically analyze the formation processes, regulatory mechanisms, influencing factors, and roles of RSMB in phytoremediation. RSMB formation unfolds in cyclical stages, including cell adhesion, microcolony formation, biofilm maturation, disintegration, and regeneration. Regulatory mechanisms are orchestrated by root exudates, which act as both nutrient sources and signaling molecules to induce microbial chemotaxis and biofilm formation ability. Additionally, communication activities among microorganisms via chemical and non-chemical signals further modulate biofilm development. RSMB formation is influenced by a combination of factors, including plant species, environmental conditions, nutrient availability, enzymes, antimicrobial peptides, biosurfactants, etc., bringing complexity to biofilm dynamics. Functionally, RSMB contributes to phytoremediation through various mechanisms. It can activate pollutants or improve plant physiology and growth to promote pollutant migration into plant systems; immobilize pollutants, degrade pollutants, or mediate pollutant volatilization to reduce pollutant migration into plant systems. Looking ahead, this review advocates for a paradigm shift toward mechanistic dissection of RSMB. We emphasizie integrating high-resolution microscopy imaging systems, multi-omics analysis techniques, and artificial intelligence simulation techniques to unravel their ecological roles and advance sustainable bioremediation approaches.