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likely to be confined to the laboratory or ‘field’ test kits, and so are unlikely to warrant concern with regard to creating their own environmental pollution.

It has already been noted that GMOs are unlikely to occupy a significant niche in bioremediation, principally due to the high cost in developing such organisms set against the low financial return on remediation. Where they are likely to be of great benefit is in solving problems for which no cheaper or simpler alternative technology is available; examples of these are not widespread.

However, genetic engineering does, and will continue to, find a role in clean technology as in examples quoted in Chapter 10. There is great potential to develop ‘designer biocatalysts’, either as isolated enzymes, or as whole cells, which should go a long way to helping industry improve its profitability and environmental profile (Burton, Cowan and Woodley 2002). The picture is also somewhat different where environmental biotechnology strays into agribiotechnology. Here the potential for the development of genetically modified plants with improved quality or increased resistance to harsh conditions or pathogens, as described in Chapters 9 and 10, is apparent.

Concerns about the safety of such constructs should be viewed in the light of discussions in Chapter 3 emphasising the natural mobility of genetic material. In nature, there is a considerable amount of genetic exchange even between unrelated organisms. A powerful example is that of the insertion of the Ti plasmid of the bacterium, Agrobacterium tumefaciens, into plant cells and another is the ‘mariner’ gene shown to have ‘jumped ‘ from tsetse fly to human (Edwards 2000). A criticism frequently levied at genetic engineering is that it crosses species boundaries, thereby transferring genes into organisms which could never be recipients. An appreciation of the potential degree of genetic rearrangement and exchange through the activities of plasmids, viruses and transposable elements leads to the conclusion that genetic engineering can be viewed as a very tiny part of the overall picture. Furthermore, considering that there is an argument suggesting a blurring between genomic and extrachromosomal genes, it seems unrealistic to describe any gene as truly ‘foreign’ when the genome is probably carrying an array of genetic material originating from a variety of sources. Generally, public alarm comes with the widespread release of large numbers of specially engineered organisms into the environment, carrying genes which may be envisaged causing an environmental problem greater than the one they seek to solve. Such examples would be GM plants carrying genes for increased herbicide or pesticide resistance.

In Chapters 9 and 10, reference was made to baculoviruses being used as insecticides. There are many reasons why this appears to be a relatively safe agent given that these nuclear polyhedrosis viruses (NPVs) are unable to infect plants, microorganisms, vertebrates, or nonarthropod invertebrates. Assuming that this argument is not invalidated by alteration to the host range, recombinant baculoviruses should be even safer, since normally the protective polyhedrin protein gene has been sacrificed in favour of the ‘foreign’ gene. This lack of

The Way Ahead 275

polyhedrin protein would be expected to lessen NPV survival in the wild and certainly reduce their infectivity thus making them poor vectors for the spread of ‘foreign’ genes.

Another area of major concern is that that many of the constructs released into the environment carry genes for antibiotic resistance. In Chapter 9, the rationale for including such genes was described but, briefly, its function is during the construction of the recombinant and, especially in eukaryotic recombinants, serves no function in the final GMO. This being the case, it can be argued that it is reasonable to require the removal of all such selector and reporter genes before release of the GMO. Accordingly, it is especially true because of the limited number of selector and reporter genes in current use. Consequently, it is likely that while the gene or genes of interest may be unique, or almost so, to that construct, it will probably be carrying one of a very limited number of selector or reporter genes. As a result, the total number of GMOs released worldwide in one year, carrying one particular selector or reporter gene could be very high indeed. Given that true figures for the rate of gene transfer between unrelated organisms (horizontal transfer) have not yet been satisfactorily estimated, it would seem prudent to err on the side of caution and remove all unnecessary genetic material, prior to GMO release.

Attempts to estimate the rate of gene transfer in the environment are being made using microcosms. These are small-scale reproductions of an enclosed test environment. One such experiment investigated the effect of simulated lightning on the rate of plasmid transfer between bacteria. Their results showed an increase in transformation suggesting that, under certain conditions, lightning is able to make bacterial cells competent to receive plasmid DNA by horizontal transfer (Demaneche 2001). Microcosms are useful test systems especially as in this example, where the question being asked is very specific, but they have their limitations in the assessment of wider horizontal gene transfer, due to the difficulties in recreating the natural environment. It seems likely that many questions regarding the spread of genes will not be answered until sufficient GMOs have been released and the ensuing results monitored. It is clear that much more research is required into the balance between real benefits and risks of genetically engineered plants (Wolfenbarger and Phifer 2000).

Closing Remarks

In the final analysis, life is enormously robust and resilient, not perhaps at an individual level, but certainly on a gross scale. Living things, and most especially microbes, have colonised a truly extensive range of habitats across the planet, and some of these are, as has been discussed, extremely challenging places. This, combined with the lengthy history of bacteria and archaea, which has equipped many species with an amazing array of residual metabolic tools, adds up to a remarkable reservoir of capabilities which may be of use to the environmental

276 Environmental Biotechnology

biotechnologist. Humanity recently celebrated the turning of the millennium – the passage of 40 generations of our species. On this basis, a bacterial ‘millennium’ passes in less than a day. There is a tendency, particularly in older biology textbooks, to describe bacteria and their kin as ‘primitive life forms’. While, of course, this is true in terms of relative organisational complexity, it can encourage a sort of unwarranted phylum-ist view of our own evolutionary superiority. With 40 generations passing in under 24 hours and predating our own earliest beginnings by several hundreds of millions of years, prokaryotes are clearly far more highly evolved than ourselves or any other form of life on earth. Unsurprisingly, then, many of the environmental problems encountered today have readily available solutions which make use of the natural cycles, pathways and abilities of entirely unaltered micro-organisms.

As this book has been at pains to point out, while there may well be a role for the use of GMOs in some applications, it seems unlikely that engineered organisms will assume centre-stage in the field. Part of the reason is that there may simply be no need; there are enough odd abilities around quite naturally. Scientists from the US Geological Survey recently announced the discovery of hydrogenotrophic archaean methanogens living 200 metres below the surface of Lidy Hot Springs, Idaho (Chapelle et al. 2002). This microbial community is unlike any previously discovered; normally arachea seldom comprise more than 1 – 2%, but here, in conditions of low organic carbon content (around 0.27 mg/l) but significant levels of molecular hydrogen, they amount to around 99% of the population. Under normal circumstances these archaeans, being less efficient energetically, are out-competed by ‘normal’ carbon-eating microbes, but in the absence of solar energy, which drives ecosystems based on utilising organic carbon, conditions heavily favour them.

This has been seen as particularly relevant to the search for extraterrestrial life, since finding living systems on earth in environments analogous to those believed to exist on Mars or the Jovan moon, Europa, could provide vital clues. In many ways, perhaps it has even more relevance as a testimony to the extraordinary biodiversity of this planet and to the enormous potential of its collective gene pool.

References

Burton, S.G., Cowan, D.A. and Woodley, J.M. (2002) The search for the ideal biocatalyst, Nature Biotechnology, 20: 37 – 45.

Chapelle, F.H., O’Neill, K., Bradley, P.M., Methe,´ B.A., Ciufo, S.A., Knobel, L. and Lovley, D.R.A. (2002) A hydrogen-based subsurface microbial community dominated by methanogens, Nature, 415: 312 – 15.

Cui, Y., Wei, Q.Q., Park, H.K., Lieber, C.M.(2001a) Nanowire nanosensors for highly sensitive and selective detection of biological and chemical species, Science, 293: 1289 – 92.

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Cui, X.D., Primak, A., Zarate, X., Tomfohr, J., Sankey, O.F., Moore, A.L., Moore, T.A., Gust, D., Harris, G. and Lindsay, S.M. (2001b) Reproducible measurement of single-molecule conductivity, Science, 294: 571 – 4.

Daniell, H. (1999) Environmentally friendly approaches to genetic engineering,

In Vitro Cellular and Developmental Biology – Plant, 35: 361 – 8. Demaneche, S., Bertolla, F., Buret, F., Nalin, F., Sailland, A., Auriol, P., Vagel,

T.M. and Simonet, P. (2001) Laboratory scale evidence for lightning mediated gene transfer in soil, Applied and Environmental Microbiology, 67: 3440 – 4.

Edwards, R. (2000) Look before it leaps, New Scientist, 24: June 5.

Tucker, C.L. and Fields, S. (2001) A yeast sensor of ligand binding, Nature Biotechnology, 19: 1042 – 6.

Wolfenbarger, L.L. and Phifer, P.R. (2000) Biotechnology and ecology – the ecological risks and benefits of genetically engineered plants, Science, 290: 2088 – 93.

Bibliography and Suggested

Further Reading

Allison, D.G., Gilbert, P., Lappin-Scott, H.M. and Wilson, M. eds (2000) Community Structure and Co-operation in Biofilms, Fifty-ninth symposium of the Society for General Microbiology held at the University of Exeter September 2000, Cambridge University Press, Cambridge.

Barrow, G.I. and Feltham, R.K.A. (1993) Cowan and Steel’s Manual for the Identification of Medical Bacteria, 3rd edition, Cambridge University Press, Cambridge.

Davidson, J.N. (1972) The Biochemistry of the Nucleic Acids, 7th edition, Chapman and Hall, London.

Evans, G.M. (2001) Biowaste and Biological Waste Treatment, James and James, London.

Glazer, A.N. and Nikaido, H. (1995) Microbial Biotechnology Fundamentals of Applied Microbiology, W.H. Freeman, New York.

Hardman, D.J., Mc Eldowney, S. and Waite, S. (1994) Pollution: Ecology and Biotreatment, Longman, Harlow.

Hughes, M.A. (1996) Plant Molecular Genetics, Longman, Harlow.

Larson, R.A. and Weber, E.J. (1994) Reaction Mechanisms in Environmental Organic Chemistry, Lewis, Boca Raton.

Lehninger, A.L. (1975) Biochemistry, 2nd edition, Worth, New York. MacPherson, G. (1995) Home Grown Energy from Short-Rotation Coppice, Farm-

ing Press Books, Ipswich.

Mandelstam, J. and McQuillen, K. (1973) Biochemistry of Bacterial Growth, 2nd edition, Blackwell Scientific, Oxford.

Nelson, D.L. and Cox, M.M. (2000) Lehninger Principles of Biochemistry, 3rd edition, Worth, New York.

Polprasert, C. (1995) Organic Waste Recycling, Wiley, Chichester.

Prescott, L.M., Harley, J.P. and Klein, D.A. (1996) Microbiology, 3rd edition, WmC Brown, Dubuque, IA.

Scragg, A. (1999) Environmental Biotechnology, Longman, Harlow.

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Twidell, J. and Weir, T. (1994) Renewable Energy Resources, Chapman & Hall, London.

White, A. Handler, P., and Smith, E.L. (1968) Principles of Biochemistry, 4th edition, McGraw-Hill, New York.