Nature's Cleanup Crew: Algal–Bacterial Partnerships in Heavy Metal-Polluted Waters

The escalating accumulation and dissemination of heavy metals (HMs) in the environmental matrices present growing ecological and public health concerns, underscoring the significance of natural process mediating their removal from environment. Among emerging biotechnological approaches, microalgae–bacteria consortia have garnered significant attention as naturally occurring, sustainable systems for the remediation of HMs and organic pollutants in industrial and municipal wastewaters. Despite their promise, the underlying mechanisms that govern microalgae–bacteria interactions, particularly under stress from emerging pollutants and during HM removal remain inadequately understood. Two primary modes of interaction, physical associations and molecular-level communications, are fundamental to their co-adaptation, survival, and functional synergy. These interactions encompass extracellular and intracellular processes such as chemotaxis, quorum sensing, transcriptomic reprogramming, and genetic adaptation. This review synthesizes current knowledge on the dynamic interplay within microalgae–bacteria systems, emphasizing their mechanistic roles in metal sequestration. We presented recent advancements to deepen our understanding of these interactions and support the development of efficient and sustainable biotechnologies for environmental remediation and resource recovery.