Team:Edinburgh/ethics(biosafety)

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OUR APPROACH TO THE ISSUES OF BIOLOGICAL SAFETY ASSOCIATED WITH THE PROJECT

Our project ideas would hardly raise safety issues in terms of researcher or public safety. Escherichia coli strains used are standard disabled laboratory strains which are not capable of colonising the human intestines. Inserted genes in the strains encode regulatory elements, bioluminescence proteins, and proteins involved in degradation of nitro-compounds. They are not expected to have any effect on pathogenesis or raise any other safety issues. The resulting gene-modified organism is not expected to be more hazardous than the parent organism. However, as soon as the last stage of our project implies the release of genetically engineered microorganisms in the environment, ecological considerations must be taken into account when implementing this stage.

In advance of work starting we submitted risk assessment form for activities involving the use of genetically modified micro-organisms to School GM Safety Committee of the University of Edinburgh. You can download this document here.

Synthetic biology techniques allow genetic constructs to be inserted into or removed from genomes of genetically engineered microorganisms (GEMs). Introduced genes and regulatory sequences could, theoretically, come from any living source or be synthetically produced. Organisms combining novel traits might be more likely to display novel ecological properties. There is a need to ensure that GEMs do not damage the ecosystems to which they are released (see figure 1).

Figure 1. A summary of the relationships between risk and the ecological properties of genetically modified microorganisms. Taken from [2].

Survival and persistence of GEMs in soil Many factors influence the survival and persistence of microorganisms released into the environment. Some can survive for very long periods in adverse conditions as dormant spores or cysts ; others persist in a viable but non-culturable state without forming such structures. For example, after inoculation of E. coli in soil at 5°C their numbers declined gradually and reached the detection limit at day 68. At 25°C, the detection limit was reached at day 26 after inoculation. As there are the vast array of environmental factors influencing GEMs, both biotic (competition and predation) and abiotic (temperature, pH, moisture and adsorption), it is understandable that deriving a competent modeling scheme for the survival of our gene-engineered microorganism will be a daunting task.

GEMs which have genes deleted from their genome are generally less risky than those with added genes, and might even be safer than the conventional micro-organisms which they replace. Biological containment can make prolonged persistence of GEMs unlikely by, for example the use of suicide vectors or release into an environment which is only temporarily favourable, such as in the presence of a host crop. GEMs will also typically have a decrease level of fitness due to the extra energy demands imposed by introduced foreign DNA, and will therefore unable to compete under real-world conditions.

Monitoring of the survival and spread of GEMs

Monitoring the survival and spread of GEMs introduced into the environment might be difficult or impossible. Our use of the lux-based system affords several advantages for monitoring survival and spread processes:
1) bioluminescence is easily detected and requires no substantial input of expensive or obscure survey devices;
2) the production of bioluminescence by our synthetic organism is completely self-contained, no exogeneous addition of chemicals or co-factors are required;
3) bioluminescence can be monitored directly online, providing a continuous, near real-time profile of the bioremediation process;
4) the use of intact microbes as chemical sensors allows for the monitoring of contaminant bioavailability rather than just contaminant presence. This is in contrast to analytical techniques that may determine contaminant presence in an environmental matrix, but without providing information as to the biological effect of the contaminant. Such data becomes extremely important when attempting to assess detrimental health effects of TNT on exposed populations, human or otherwise.

Gene transfer

The likelihood and consequences of gene exchange between GEMs and other organisms needs to be assessed, especially when toxin transgenes are involved. Once released GEMs can be expected to evolve in ways that are beneficial to their own survival. There may be strong selection pressure for modifications that allow escape from debilitating effects imposed by biological or physical containment. Generally it makes sense to accept the likely persistence of GEMs or their transgenes after release in the environment and minimize the associated risks accordingly.

Effect of GEMS on ecosystems

Because little is known about the effects of species diversity on ecosystem processes the added effects of introducing GEMs will be difficult, if not impossible, to predict. There needs to be more research on the role of biodiversity in maintaining and regulating ecosystem functions, especially those which are life supporting. This will help us to understand the potential for syntethic biology to have adverse effects on ecosystem structure and function.

Each GEM should continue to be assessed on a case-by-case basis. Furthermore, account might need to be taken of genotype x environment interactions if the GEM is destined for widespread release. It should be remembered that where the large scale releases of GEMs are concerned, even events with very low probability might occur with sufficient frequency to cause harm. In appropriate conditions GEMs will reproduce, evolve and transfer genetic material to other organisms in the environment. Mistakes, therefore, might have permanent consequences

Despite of all the hazards associated with releasing novel organisms one must not lose sight of the fact that most GEMs are probably more likely to be beneficial than harmful. Furthermore, taking risks is a part of life we all accept to some extent. When deciding on acceptable levels of risk we should take into account the potential benefits of the GEMs.

References

1.D. Cools, R. Merckxa, K. Vlassaka and J. Verhaegen. (2001). Survival of E. coli and Enterococcus spp. derived from pig slurry in soils of different texture. Applied Soil Ecology 17, 53-62.

2.Giddings, G. (1998). The release of genetically engineered microorganisms and viruses into the environment. New Phytologist 140, 173–184.

3.Sayler, G. S., Ripp, S. (2000). Field applications of genetically engineered microorganisms for bioremediation processes. Current Opinion in Biotechnology 11, 286-289.

4.Droge, M., Puhler, A., & Selbitschka, W. (1998). Horizontal gene transfer as a biosafety issue: A natural phenomenon of public concern. Journal of Biotechnology 64, 75–90.

5.Jansson J.K. (1995). Tracking genetically engineered microorganisms in nature. Current Opinion in Biotechnology 6, 275-283.

Edinburgh University iGEM Team 2009