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EC-sponsored Research on Safety of Genetically Modified Organisms - A Review of Results
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Bioremediation
Cleaning up polluted environments:
how microbes can help


Introduction


V. de Lorenzo,
CSIC, Centro Nacional de Biotecnología,
Madrid (ES)

The development of the gene cloning technology by Cohen and Boyer in the early 1970s constituted a revolution for all of the biological sciences, seeded new industries based on these sciences, and ushered in the era of biotechnology. Though the mainstream of effort in the late 1970s lay in the development of contained bioreactor-based biotechnological applications, during the 1980s interest in developing recombinant plants and micro-organisms for uncontained environmental applications, such as waste disposal, grew rapidly. This in turn ignited a scientific and public debate on possible ecological risks of such applications and stimulated the extension of research in microbial ecology.

The use of recombinant organisms for environmental applications differs from that for contained applications in several important respects. Instead of being propagated as a monoculture in an optimised, controlled environment with nutrients in excess, the recombinant organism is introduced into a community of diverse organisms where it must establish itself, interact with other members of the community in unknown ways, and face a multitude of poorly controllable external factors, some of which place it under considerable stress. Some environmental situations encountered in bioremediation, are patently hostile for the recombinant organism. Thus, whereas contained applications are mainly based on a few well-characterised micro-organisms such as Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae and some cell lines which perform well in bioreactors, open applications are based on a more diverse range of organisms able to survive and perform in natural communities in the environment, such as Pseudomonas, Alcaligenes, etc. Efforts in the early 1980s focused on the development of new plasmid vectors based on broad host range replicons. However, these vectors suffered from the disadvantages generally common to plasmids. The specific characteristics of open biotechnological applications clearly necessitated the development of novel genetic tools and concepts to engineer new properties and meet the new challenges. Among others, these included stability without selection, minimal physiological burden, small size non-antibiotic selection markers, minimal lateral transfer of cloned genes to indigenous organisms, and traceability of specific genes and strains in complex ecosystems.
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In this context it comes as little surprise that many of the efforts of the various EC-supported projects summarised in this chapter were devoted to developing not only genetic and biochemical tools, but also to conceptual instruments to deal with two major questions. First, can we construct GMOs for release in bioremediation with an acceptable degree of ecological predictability? Second, can we monitor the performance of GMOs within a complicated environment, in particular in terms of their survival, gene transfer potential and impact on the native microbial population? As is often the case in scientific research, the original questions have given rise along the way to still more interesting ones concerning microbial ecology and biodiversity that were perhaps not anticipated to begin with. Nevertheless, the results of the various projects discussed in this chapter clearly indicate two major conclusions. First, that there is little scientific basis on which to consider microbial GMOs as agents intrisincally different from their non-recombinant counterparts. In most cases, microbes designed for bioremediation processes have been manipulated to acquire in the laboratory, in a short period of time, properties that would have otherwise evolved naturally over a much longer period of time. Second, no evidence has been found that the deliberate release of GMOs for bioremediation has caused a measurable negative impact on the natural microbial community. The consequence is that the frequently inflated concept of risk assessment, which has fuelled so much controversy and triggered so many research efforts for a decade, has moved towards the more rational area of microbial ecology and has given a remarkable new value to this otherwise neglected field.

Although the two conclusions above are in general (using the scientific jargon) negative results, they are in fact the pillars that allow us to shift the emphasis of research in biodegradation and bioremediation from such risk assessment to much more meaningful biological and ecological questions. Fortunately, the public has anticipated such a shift much earlier than the normative bodies. These are sometimes reluctant to accept that, on the basis of research that has been going on for many years now in Europe (mostly under EC sponsorship) and elsewhere, there are very few risks (if any at all) in the use of GMOs in bioremediation – certainly far less than letting pollution go untreated. As reflected in the last Eurobarometer survey, on the social perception of biotechnology, biological research for environmental remediation is precisely the application of genetics that Europeans sympathise with the most and are least concerned with regarding risks.
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How can Europe capitalise on the intellectual potential, the excellent research and the vigorous networking that the EC-supported bioremediation activities have created over the years in the various Framework Programmes? We are in a privileged position to move now towards the new challenges of biodiversity and microbial ecology. Important for us as it is, human genetics and human genes in fact contribute very little to the extraordinary biological diversity of the biosphere. We know nearly nothing (perhaps less than 0.1%) of the overall genetic pool of planet Earth. While we know much about animal and plant diversity, the microbial word (that may contribute over 80% of the total biomass on the planet) is still a terra incognita, due mostly to our failure to access micro-organisms that cannot be easily cultivated with traditional techniques. The growing demand for medicaments for human health, and novel biocatalysts for industry and environmental preservation and remediation places entirely new significance on the exploration of microbial diversity as a veritable activity mine. There, the bulk of unknown life forms, enzymes and bioactive molecules lie waiting to be discovered and applied for the benefits of humans and industrial opportunities. If the many techniques and concepts that have emerged from the projects summarised in this chapter can be harnessed and made to join forces with the novel genomic approaches currently emerging, together they will provide materials and conceptual tools to tackle the challenge of accessing microbial biodiversity with an entirely new strength.

As a final reflection on research on microbes destined for environmental release, let me share my feeling that a major source of innovation in the next decade will originate at the interfaces of (molecular) microbiology with what one may call traditional industrial disciplines such as agriculture, mining, materials science and industrial waste management. Although the direct impact on citizens’ lives may not be quite the same as that of new medicaments, the possibilities in these areas are immense. Microbial alternatives to chemical pesticides and fertilisers, bacteria that specifically remove sulphur atoms from fossil fuels, or microbes designed to convert extremely toxic chemicals into valuable products, are just a few of the many movements we will witness in years to come.

 
 
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