(430d) Contrasting the Metabolic Capabilities of Cyanobacterial Strains for Assessing Bio-Production Platform Selection

Cyanobacteria are photoautotrophic prokaryotes that exhibit robust growth under diverse environmental conditions with minimal nutritional requirements. They can use solar energy to convert CO2 and other reduced carbon sources into a variety of biofuels and chemical products. The Cyanothece genus of cyanobacteria has been shown to offer very high levels of hydrogen production and nitrogen fixation. Here we reconstruct and subsequently analyze and contrast the differences in metabolism between five Cyanothece strains, namely Cyanothece 7424, 7425, 7822, 8801 and 8802. We compare these phylogenetically related Cyanothece strains to assess their suitability as microbial production platforms. Reconstructed genome-scale metabolic models include experimentally verified biomass compositions, fully traced photosynthesis reactions and respiratory chains as well as balanced reaction entries and GPR associations. From the reconstructed models, we find Cyanothece strains share almost 90% of their reactions. Common reactions are mainly involved in nitrogen fixation, central carbon metabolism, photosynthesis and respiration, amino acid biosynthetic pathways as well as bidirectional hydrogenase activity. All but Cyanothece (7424 and 7822) have complete alkane production pathways. Furthermore, all these strains share a non-fermentative higher-alcohol production pathway. Cyanothece 7425 is phylogenetically most distant among these Cyanothece strains, reflected in the 332 unique reactions not shared with the other Cyanothece strains. By focusing on the specific differences among these Cyanothece strains, our models reveal exactly which steps are the ones absent in fermentative Butanol production pathway. Specifically, Cyanothece 7425 has the most complete pathway missing only the conversion between 3-Hydroxybutanoyl-CoA and Crotonoyl-CoA, while Cyanothece 7822 lacks a step dealing with the conversion between Crotonyl-CoA and Butanoyl-CoA. Another notable difference is the presence or absence of the glyoxylate shunt in the TCA cycle. Cyanothece (7425, 8801 and 8802) do not have the glyoxyate shunt, whereas Cyanothece (7424 and 7822) appear to have all relevant enzymes. Herein, we describe results from comparing important pathways leading to biofuel or other useful product formation followed by experimental verification.