Carbon and nitrogen metabolism in cyanobacteria: Basic traits, regulation and biotechnological application

Cyanobacteria constitute a coherent phylogenetically group into Bacteria domain, displaying great morphological, physiological and metabolic diversity. Further to carbon-fixation via oxygenic photosynthesis, certain cyanobacteria also perform biological nitrogen (N) fixation, contributing for key cell metabolic processes. CO2 is the primary carbon (C) source, however sugar and other organic C can also be used by cyanobacteria. Considering N, a variety of sources are metabolized. C and N metabolism must be therefore tightly coupled and precisely regulated. Thus, coordinated control mechanisms involving both metabolisms, avoiding limitation or oversupply, are present in cyanobacteria. Here, we briefly characterize and further discuss the regulatory principles underlying C and N metabolisms, highlighting how cyanobacterial cells sense their sources/concentrations, controlling their transport, assimilation and usage. Furthermore, we highlight how and to which extent the understanding of C/N balance contribute for optimum growth and production of specific compounds with biotechnological application in different cyanobacteria.