Bio‐risk assessment research on genetically engineered cyanobacteria for sustainable biofuels

Genetically engineered (GE) cyanobacteria are an attractive photosynthetic platform for sustainable biofuels and bioproducts. A number of biofuels such as ethanol, isobutanol, and 1‐butanol have been experimentally produced using GE cyanobacteria. Even though this approach is promising, there are still questions regarding the biosafety of these GE organisms. What happens to the plasmids that are used for introducing transgenes into the cyanobacterial cells? Studies have shown that E. coli can transfer plasmids into cyanobacteria. We are interested in knowing if the reverse direction is possible? Furthermore, can the transgenes be horizontally transferred into other organisms after they are already integrated into the genomic DNA of the cyanobacteria? These questions need to be addressed before this approach can be commercialized. In order to answer these questions, we conducted an experiment by co‐incubating wild‐type E. coli DH5α with different sets of GE Thermosynechococcus elongatus BP1 carrying either plasmid transgenes or solely integrated transgenes. The transfer event was monitored using selection markers. Our results showed that the transgenes in the form of plasmids were transferred from these GE cyanobacteria into wild‐type E. coli DH5α even without the help of a nitrocellulose membrane while there was no detectable transfer event for the integrated transgenes observed so far. In addition, the frequency of the plasmid transfer event appeared to decrease gradually over time. These results suggested that even though GE cyanobacteria carrying integrated transgenes possess a more permanent change in the genomic DNA, the bio‐risk of these GE organisms in the context of gene sharing is less severe than plasmids‐carrying GE cyanobacteria. Support or Funding Information This work is supported by Biotechnology Risk Assessment Grant Program competitive grant award no. 2016‐33522‐25624 from the U.S. Department of Agriculture to JWL and LHG. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .