Systems Biology of a Cyanobacterial Chassis for Photosynthetic Biosynthesis
Cyanobacteria, a broadly distributed class of photosynthetic bacteria, are attractive candidates for development as “chassis organisms” for production of biofuels and other products. In comparison to photosynthetic algae, cyanobacteria grow more quickly, are capable of growth in a broad range of conditions, and possess much simpler (and thus more easily engineered) genomes. However, developing systems-level understanding of integrated metabolic networks in cyanobacteria will be necessary before more sophisticated bioengineering approaches can be applied to further optimize performance or more easily introduce new biosynthetic modules. A new study by researchers at Washington University examines systems biology properties of the recently discovered cyanobacterial strain Synechococcus elongatus UTEX 2973, which grows at double the rates of other members of this species under high light intensities. Using a comparative genomics approach, the team was able to identify a surprisingly small set of genetic differences between UTEX 2973 and slower growing S. elongatus strains, amounting to 55 amino acid substitutions and a small missing region encoding six genes seen in the slower growing strains. Leveraging capabilities at the Department of Energy’s Environmental Molecular Sciences Laboratory, these findings were validated using global proteomics analysis, confirming predicted amino acid substitutions and showing that UTEX 2973 is missing five of the six predicted proteins. Although these proteins are currently of unknown function, UTEX 2973 fails to form cytoplasmic glycogen granules observed during growth of the other strains. This observation suggests that UTEX 2973 may not store photosynthetically fixed carbon, but instead immediately uses it as substrate fueling accelerated growth. UTEX 2973 can be genetically manipulated using tools developed for related cyanobacterial strains, and the team currently is developing a mutant library to explore the specific mechanistic basis of the UTEX 2973’s rapid growth phenotype. These findings expand our knowledge of cyanobacterial systems biology and present Synechococcus elongatus UTEX 2973 as a promising potential biotechnological chassis organism for the direct conversion of sunlight and CO2 into biofuels and other compounds.
Yu, J., M. Liberton, P. F. Cliften, R. D. Head, J. M. Jacobs, R. D. Smith, D. W. Koppenaal, J. J. Brand, and H. B. Pakrasi. 2015. “Synechococcus elongatus UTEX 2973, a Fast Growing Cyanobacterial Chassis for Biosynthesis Using Light and CO2,” Scientific Reports 5: 8132. DOI: 10.1038/srep08132.