The growth of genetically engineered or GE cyanobacteria may pose a risk if the transformant escapes to the environment. In an attempt to simulate the behavior of a possible escape into the environment of GE cyanobacteria with a construct containing a nitrate promoter, we conducted several growth studies. Results suggest that the presence of nitrate has an influence on the growth rate of the T. elongatus BP1 wild type and the GE T. elongatus BP1 R-Lipase-Tetracycline BY20 (or BY20). In order to determine whether the GE cyanobacteria would outcompete, co-exist or lose ground to the wild type cyanobacteria, a study was conducted by co-culturing wild type cyanobacteria with the GE cyanobacteria in medium supplemented with nitrate. Two models were used in the co-culture: one model involved the BP1 wild type vs BY20 and the other model involved Synechococcus elongatus PCC 7942 WT (or 7942 WT) vs the GE Synechocystis PCC 6803 YFP-R-Lipase-Tetracycline (or 6803 YFP). Microscopy cell counting and/or plating on tetracycline antibiotic plates were used to monitor the cells in the co-culture over time. The preliminary results from the cell count using microscopy suggested that the plasmid transformant 6803 YFP grows quicker than the 7942 WT. From an initial mixture of 7942 WT and 6803 YFP at 1:1 ratio, the 6803 YFP showed domination after a week of incubation. After two weeks of co-culturing, the 6803 YFP continued to grow faster than the 7942 WT. The control samples which involved the incubation of 6803 WT and 7942 WT showed a slight domination of 6803 WT. The preliminary results suggest that the GE 6803 YFP outcompetes the 7942 WT over time and that the domination of 6803 YFP is partially due to the difference in species. A thorough investigation is needed into the effect of transformation on the growth rate of cyanobacteria.

Competition study between wild type cyanobacteria Synechococcus elongatus PCC 7942 and plasmid transformant Synechocystis PCC 6803

2019 Spring National Meeting

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