Metabolic interactions between microalgae and bacteria: Multifunctional ecological interplay and environmental applications

Microalgae in nature facilitate the harboring of a unique niche for the bacteria living in their immediate surroundings, contain an organic carbon-rich environment called the phycosphere. This review revisited microalgal-bacterial interactions and metabolic exchange by covering various examples and identifying gaps in our understanding and implications of algal-bacterial interactions across a broad spectrum from ecology to biotechnology. There is a wide diversity in the types of interactions (positive and negative) between microalgae and bacteria, the nature of exo-metabolites, and the ecological functions of metabolic exchange. In addition, host specificity of the phycospheric bacteria and the mediation of phages in the algal-bacterial interactions are some of the fascinating questions wherein more research is needed. Some of these interactions have implications that could be harnessed to improve competence for biofuels (electro-biofuel, biohydrogen, bioethanol, and biodiesel) production, stress mitigation, and the repertoire of bioremediation strategies for pollutants. Beside these, advanced omics technologies and synthetic ecology provide solutions not only to understand the vivid exometabolic and algal-bacterial interactions for devising new applications but also to unfold the multi-functions of metabolites in varying ecological settings.