Applications of bacterial quorum sensing in algal biotechnology

Quorum sensing (QS) is the ability of bacteria to communicate and coordinate their behavior via the production of signal molecules, and it is dependent on the local cell density. QS plays vital roles in the regulation of cellular functions in bacteria such as gene expression, formation of biofilms, production of antimicrobial compounds, resistance to antibiotics, and interaction with other organisms such as microalgae. The bacterial interactions with microalgae and cyanobacteria can be either beneficial or detrimental, and these are utilized for various biotechnological applications. The notable applications include large-scale production of microalgal biomass, algal by-products, phytohormones, enhancement of lipid production for biofuel, and improvement of microbial fuel cells' performance for electricity production and algal hydrogen production. In addition, bacterial–algal interactions are utilized for the removal of pollutants from wastewater and the improvement of microalgal harvest through aggregate formation. The metabolites produced from the microalgae are used as quorum sensing inhibitors (QSIs) to control the biofilm formed by bacterial pathogens. Conversely, the QS bacteria are also used for controlling harmful algal blooms. In general, the biological applications of algal biotechnology related to QS and interactions with bacteria are promising in various fields from biomass production to environmental management. Moreover, the results obtained from the previous studies showed that the algal–bacterial consortia have clear advantages over monoculture in terms of biomass production and accumulation of bioproducts. However, the current studies on the biological applications of QS in algal biotechnology focus much on the conceptual design and testing hypothesis, but the studies lack explorations for commercialization and scale-up productions, which needs to be considered in the future studies.