Cyanobacteria are photosynthetic microorganisms whose metabolism can be manipulated through genetic engineering for the production of many molecules of interest to industry directly from CO
2 and sunlight
1,2. However, the costs of constructing and maintaining photobioreactors for scaled up cultivation of these genetically modified cyanobacteria are cost prohibitive
3. A major concern for the cultivation of cyanobacteria in more affordable open pond reactors is the escape and subsequent environmental contamination by these genetically modified cyanobacteria. Modelling and preliminary experimental results suggest that a potentially useful strategy for containment of genetically modified cyanobacteria could involve abolishment of function the native CO
2-concentrating mechanism (CCM) through gene knockouts, thereby eliminating the ability to fix CO
2 in ambient air but causing no reduction in CO
2-fixation rate under an artificially elevated CO
2 concentration
4. In the first part of this work, the efficacy of this method was studied for a model cyanobacterium,
Synechococcus sp. PCC7002. The genes eliminated in this method have homologs across a wide diversity of cyanobacteria. Thus, a probable mechanism for subversion of containment would involve horizontal gene transfer to restore CCM function. In the second part of this work, elimination of genes associated with the natural competency of
Synechococcus sp. PCC7002 was examined as a method to decease the likelihood of this subversion. The final result of this work is a strain of cyanobacteria engineered to have high fitness in an industrial environment containing high-CO
2, an inability to propagate in the surrounding environment, and a low likelihood of restoring viability in ambient air.
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3. Jones, M. E. & Banholzer, W. F. Solar flux, water, and land impose limits on biology. Biotechnol. Bioeng. 111,1059â??61 (2014).
4. Clark, R., Cameron, J., Root, T. & Pfleger, B. Insights into the industrial growth of cyanobacteria from a model of the carbon-concentrating mechanism. AIChE J. 60, 1269â??1277 (2014).
