GTP-binding protein Era: a novel gene target for biofuel production

Background: Biodiesel production using cyanobacteria is a promising alternative to fossil fuels. In this study we created a transposon library of Synechococcus elongatus PCC 7942 in order to identify novel gene targets for enhanced fatty acid and hydrocarbon production. The transposon library was subsequently screened for desirable traits using macro- and microscopic observations as well as staining with the lipophilic dye Nile Red. Results: Based on the screening results, we selected a single mutant, which has an insertion in the gene encoding for the GTP-binding protein Era. We subsequently verified the phenotype-genotype relation by overexpression, reintroducing and complementing the mutation. Overexpression of era caused a reduction in the cell size in the late exponential phase of growth and an increase in the total amount of intracellular fatty acids. Reintroduction of the inactivated transposon caused a significant increase in the cellular length as well as changes in the amounts of individual hydrocarbons and fatty acids. Ectopic complementation of this mutation fully restored the hydrocarbon production profile to that of wild-type and partially restored the fatty acid production. Moreover, the cellular size was significantly smaller than that of the inactivated transposon mutant. Conclusions: The GTP-binding protein Era has never been studied in cyanobacteria and proved to be an essential gene for S. elongatus PCC 7942. We also found that this protein is important for hydrocarbon and fatty acid metabolism as well as determination of the cell size in PCC 7942. Our results suggest that the GTP-binding protein Era can be used as a novel target for further improvement of biofuel precursors production.