467630 A Strain Engineering Strategy for the Containment of Genetically Modified Cyanobacteria

Friday, November 18, 2016: 2:00 PM
Continental 7 (Hilton San Francisco Union Square)
Ryan L. Clark1, Thatcher W. Root1 and Brian F. Pfleger2, (1)Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, WI, (2)Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI

Cyanobacteria are photosynthetic microorganisms whose metabolism can be manipulated through genetic engineering for the production of many molecules of interest to industry directly from CO2 and sunlight1,2. However, the costs of constructing and maintaining photobioreactors for scaled up cultivation of these genetically modified cyanobacteria are cost prohibitive3. 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 CO2-concentrating mechanism (CCM) through gene knockouts, thereby eliminating the ability to fix CO2 in ambient air but causing no reduction in CO2-fixation rate under an artificially elevated CO2 concentration4. 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-CO2, an inability to propagate in the surrounding environment, and a low likelihood of restoring viability in ambient air.

1. Angermayr, S. A., Gorchs Rovira, A. & Hellingwerf, K. J. Metabolic engineering of cyanobacteria for the synthesis of commodity products. Trends Biotechnol. 33,352–361 (2015).

2. Sarkar, D. & Shimizu, K. An overview on biofuel and biochemical production by photosynthetic microorganisms with understanding of the metabolism and by metabolic engineering together with efficient cultivation and downstream processing. Bioresour. Bioprocess. 2,17–36 (2015).

3. Jones, M. E. & Banholzer, W. F. Solar flux, water, and land impose limits on biology. Biotechnol. Bioeng. 111,1059–61 (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, 1269–1277 (2014).

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