Metabolic Pathway Engineering in Cyanobacteria for Environmental Applications

Cyanobacteria have an efficient and well-controlled metabolic architecture. Their abilities to adapt to harsh environments and unpredictable stresses have led to the development of sophisticated molecular editing tools to fully harness their machinery for diverse applications. Improved knowledge of cellular metabolism under heavy metal stress, pollutant removal, and salt tolerance utilizing omics-based techniques is crucial for manipulating cyanobacteria’s genome for environmental applications. This chapter covers the elucidation and engineering of the molecular pathways in cyanobacteria for removal of heavy metals, phosphorus, and excessive salts. Promoter systems, ribosome-binding sites (RBSs), CRISPR interference (CRISPRi), and synthetic short regulatory RNA (sRNA) are among the well-established regulatory tools in cyanobacteria. A promising strategy for creating multi-knock-in marker-free mutants in Escherichia coli, serine integrase recombinational engineering may soon be investigated in cyanobacteria. Synthetic genetic circuits that operate as Boolean logic functions have been built in model strains, while these circuits allow switch-like control over gene expression in response to environmental inputs. The possibility of elucidating and manipulating the resistance mechanisms has also been discussed as a tool to improve cyanobacterial bioremediation capabilities. Lastly, possible obstacles and opportunities for enhancing cyanobacteria-based bioremediation of heavy metals, phosphorus, and excessive salts are also highlighted.