Peebles Lab
Colorado State University
Cyanobacteria Biotechnology
Cyanobacteria are photosynthetic microbes
Cyanobacteria utilize sunlight and atmospheric carbon dioxide (CO2) to grow. This makes them an attractive chassis for chemical production because of the renewable nature of sunlight availability and the carbon sequestration process of cyanobacterial growth.
​
Our lab works with Synechocystis sp. PCC 6803, a fresh-water cyanobacterium with a fully-sequenced, genetically-tractable genome and a relative fast growth rate.
Genetic engineering in cyanobacteria is challenging due to the lack of tools available
A large majority of the genetic tools available to engineers have been developed in heterotrophs like E. coli and yeast. Genetic tools can be implemented to provide control over transcription (e.g. promoters), translation (e.g. ribosome binding sites), and protein activity (e.g. codon optimization strategies and design). However, many of the standard tools effective in heterotrophs do not perform as expected in photoautotrophs, like cyanobacteria.
Our lab has worked to identify, develop, and characterize new genetic tools for use in cyanobacteria. We have developed a promoter library of induction strength (see Albers et al. (2014) J. Biotechnol.), and characterized PpsbA2 and PpsbA3 for heterologous gene expression from chromosomal neutral sites (see Albers et al. (2016) Biotechnol. Prog.). We also built a counter-selection method for markerless integration into the Synechocystis genome (see Cheah et al. (2013) Biotechnol. Prog.).
Biofuel production in cyanobacteria is different under continuous light laboratory conditions and diurnal light-dark cycles
Industrial production strains of cyanobacteria will likely be grown in outdoor cultivation systems so that they can use sunlight--the renewable resource cyanobacteria utilize which makes them so interesting in the first place.
​
Natural sunlight availability goes through diurnal light-dark cycles: the run rises, peaks at midday, sets, and there is no sunlight available at night. These light conditions are drastically different than the continuous low-light conditions of most laboratories.
​
We found that daily light-dark cycles had a diminishing effect on engineering free fatty acid productivity in Synechocystis (see Cheah et al. (2016) Algal Res.). We are currently working to understand how daily light-dark cycles affect cellular metabolism and developing genetic engineering tools tailored to these dynamic conditions.