The Cyanobacterial Core-genome: Global and Specific Features with a Focus on Secondary Metabolites
Stefan Simm, Enrico Schleiff and Rafael Pernil
from: Cyanobacteria: Omics and Manipulation (Edited by: Dmitry A. Los). Caister Academic Press, U.K. (2017) Pages: 1-34.
Cyanobacteria are a prolific source of natural products and produce a vast array of compounds, including many notorious toxins as well as natural products of huge interest to pharmaceutical and biotechnological industries. Genome mining has enabled the identification and characterization of natural product gene clusters, and mechanisms that are unique to cyanobacteria, or rarely seen in other organisms, have been discovered. Many cyanobacterial secondary metabolites are cyanotoxins, which show a broad range of chemical structures and biological activities, but in addition to toxin production, also several NRPS and PKS gene clusters are devoted to important cellular processes in cyanobacteria such as iron uptake and nitrogen fixation. Most of the biosynthetic clusters identified here have unknown end products, highlighting the power of genome mining for the discovery of new secondary metabolites. These studies show that cyanobacteria encode a huge variety of cryptic gene clusters involved in the production of natural products, and the known chemical diversity to date is likely to be only a fraction of the true biosynthetic capabilities of this fascinating and ancient group of organisms. Furthermore, mechanistic insights obtained from the biochemical studies of cyanobacterial pathways can inspire the development of concepts for the design of bioactive compounds by synthetic-biology approaches in the future. Here, we survey the biosynthetic pathways of the top five most researched cyanobacterial species with the most extensive literature, including Microcystis aeruginosa NIES-843, Synechocystis sp. PCC 6803, Anabaena sp. PCC 7120, Arthrospira platensis NIES-39 and Synechococcus elongatus PCC 7942. These analyses have enabled the identification of biosynthetic gene clusters for structurally diverse metabolites, including non-ribosomal peptides, polyketides, ribosomal peptides, terpenes and fatty acids. We highlight the unique enzyme mechanisms that were elucidated or can be anticipated for the individual products, but further include different classes of secondary metabolites from cyanobacteria other than NRPS and PKS read more ...