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Environmental and food safety issues of genetically modified crops.
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Managing to harvest? Perspectives on the potential of aquaculture.
Aquaculture has been one of the most rapid and technically innovative of food production sectors globally, with significant investment, scientific and technical development and production growth in many parts of the world over the past two decades. While this has had a significant effect on the global supply of aquatic food products and had an important impact in rural and urban food supply and employment in many developing economies, growth and increasing internationalization has not been without concern for natural resource use, environmental impact and social disruption. The expectations for production and diversification are now significant and while the scientific and technical means are already available to meet much of the intended targets, practical constraints of investment, profitability, resource access and system efficiency are likely to become far more important constraints for the future. This review offers a contemporary perspective on the ways in which the sector might develop, its interactions with constraints and the strategies that may be required to ensure that future development is both positive and sustainable.
Patenting biotechnology: ethical and philosophical issues.
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In situ survival of plasmid-bearing and plasmidless Pseudomonas aeruginosa in pristine tropical waters.
Two rare wild-type strains of Pseudomonas aeruginosa were mixed in membrane diffusion chambers and then introduced into a natural freshwater environment for 72 h. The plasmid-containing strain (R serotype 15) and the plasmidless strain (H serotype 5) had initial bacterial densities of 2 x 10(5) cells per ml. Samples collected from the chambers were analyzed for viable and direct counts and for acquired-resistance frequencies. Suspected transconjugant-to-donor ratios ranged from 0.5 to 1.3; transfer percentages ranged from 13 to 70%. [3H]thymidine uptake indicated DNA synthesis in both strains as well as in transconjugants. These studies indicate that rare wild-type bacterial strains with large plasmid loads can survive as well as can bacteria with low plasmid loads when exposed to the in situ conditions of a tropical freshwater habitat. These results also suggest that genetic modification of indigenous microbiota through conjugation or transformation is feasible when rare wild-type strains or genetically engineered microorganisms are released in large numbers in tropical aquatic ecosystems.
Influence of earthworm activity on gene transfer from Pseudomonas fluorescens to indigenous soil bacteria.
We have developed a model system to assess the influence of earthworm activity on the transfer of plasmid pJP4 from an inoculated donor bacterium, Pseudomonas fluorescens C5t (pJP4), to indigenous soil microorganisms. Three different earthworm species (Lumbricus terrestris, Lumbricus rubellus, and Aporrectodea trapezoides), each with unique burrowing, casting, and feeding behaviors, were evaluated. Soil columns were inoculated on the surface with 10(8) cells per g of soil of the donor bacterium, and after a 2-week incubation period, donor, transconjugant, and total bacteria were enumerated at 5-cm-depth intervals. Transconjugants were confirmed by use of colony hybridization with a mer gene probe. In situ gene transfer of plasmid pJP4 from P. fluorescens C5t to indigenous soil bacteria was detected in all inoculated microcosms. In the absence of earthworms, the depth of recovery was limited to the top 5 cm of the column, with approximately 10(3) transconjugants per g of soil. However, the total number of transconjugants recovered from soil was significantly greater in microcosms containing either L. rubellus or A. trapezoides, with levels reaching about 10(5) CFU/g of soil. In addition, earthworms distributed donor and transconjugant bacteria throughout the microcosm columns, with the depth of recovery dependent on the burrowing behavior of each earthworm species. Donor and transconjugant bacteria were also recovered from earthworm casts and inside developing cocoons. Transconjugant bacteria from the indigenous soil microflora were classified as belonging to Acidovorax spp., Acinetobacter spp., Agrobacterium spp., Pasteurella spp., Pseudomonas spp., and Xanthomonas spp.
Precautionary approaches to the appraisal of risk: a case study of a genetically modified crop.
There are strong scientific reasons for holding the broader scope of precautionary approaches to be more consistent with the scientific foundations of rational choice and probability theory than are conventional narrow risk-assessment techniques. The imperatives both of science and precaution can be seen to pull in the same direction. The regulatory appraisal of risk should become more systematic and broader in scope. In particular, a set of criteria can be developed concerning the need for greater humility, completeness, transparency, and participation in regulatory appraisal, with specific attention to the comparison of different options (including mixtures of options), the consideration of benefits and justifications, and the systematic "mapping" of the ways in which different framing assumptions lead to different pictures of performance. A case study of a pilot exercise applying a multi-criteria mapping method to the regulatory appraisal of a genetically modified crop is reported. The results are more complete than orthodox risk assessment, in that they embody consideration of an unlimited array of issues and include consideration of a wide range of different strategic alternatives to the use of GM technologies. It is concluded that conventional regulatory appraisal might be adapted to better address the imperatives of both science and precaution.
Coming to grips with a slippery issue: human waste disposal in cold climates.
Problems associated with sewage treatment and human wastes at high latitudes are briefly reviewed. In view of the fact that E. coli and other faecal bacteria can survive in the snow and the coastal waters of polar regions, several methods of how to deal with sewage outfalls in the Arctic and Antarctic are compared and discussed. Some consequences of raw sewage on the health of captive populations of a variety of Antarctic invertebrates and fish are described. Locomotion and respiration appear to be most affected. However, gaps, both in understanding the biological impact of human sewage on polar ecosystems and in finding optimal solutions for the disposal and treatment of the wastes generated by people who live in polar settlements, unfortunately still remain.
Plant responses to drought, salinity and extreme temperatures: towards genetic engineering for stress tolerance.
Abiotic stresses, such as drought, salinity, extreme temperatures, chemical toxicity and oxidative stress are serious threats to agriculture and the natural status of the environment. Increased salinization of arable land is expected to have devastating global effects, resulting in 30% land loss within the next 25 years, and up to 50% by the year 2050. Therefore, breeding for drought and salinity stress tolerance in crop plants (for food supply) and in forest trees (a central component of the global ecosystem) should be given high research priority in plant biotechnology programs. Molecular control mechanisms for abiotic stress tolerance are based on the activation and regulation of specific stress-related genes. These genes are involved in the whole sequence of stress responses, such as signaling, transcriptional control, protection of membranes and proteins, and free-radical and toxic-compound scavenging. Recently, research into the molecular mechanisms of stress responses has started to bear fruit and, in parallel, genetic modification of stress tolerance has also shown promising results that may ultimately apply to agriculturally and ecologically important plants. The present review summarizes the recent advances in elucidating stress-response mechanisms and their biotechnological applications. Emphasis is placed on transgenic plants that have been engineered based on different stress-response mechanisms. The review examines the following aspects: regulatory controls, metabolite engineering, ion transport, antioxidants and detoxification, late embryogenesis abundant (LEA) and heat-shock proteins.
Considerations in miniaturizing simplified agro-ecosystems for advanced life support.
Miniaturizing the Earth's biogeochemical cycles to support human life during future space missions is the goal of the NASA research and engineering program in advanced life support. Mission requirements to reduce mass, volume, and power have focused efforts on (1) a maximally simplified agro-ecosystem of humans, food crops, and microbes; and, (2) a design for optimized productivity of food crops with high light levels over long days, with hydroponics, with elevated carbon dioxide and other controlled environmental factors, as well as with genetic selection for desirable crop properties. Mathematical modeling contributes to the goals by establishing trade-offs, by analyzing the growth and development of experimental crops, and by pointing to the possibilities of directed phasic control using modified field crop models to increase the harvest index.
Phytoremediation of toxic trace elements in soil and water.
Toxic heavy metals and metalloids, such as cadmium, lead, mercury, arsenic, and selenium, are constantly released into the environment. There is an urgent need to develop low-cost, effective, and sustainable methods for their removal or detoxification. Plant-based approaches, such as phytoremediation, are relatively inexpensive since they are performed in situ and are solar-driven. In this review, we discuss specific advances in plant-based approaches for the remediation of contaminated water and soil. Dilute concentrations of trace element contaminants can be removed from large volumes of wastewater by constructed wetlands. We discuss the potential of constructed wetlands for use in remediating agricultural drainage water and industrial effluent, as well as concerns over their potential ecotoxicity. In upland ecosystems, plants may be used to accumulate metals/metalloids in their harvestable biomass (phytoextraction). Plants can also convert and release certain metals/metalloids in a volatile form (phytovolatilization). We discuss how genetic engineering has been used to develop plants with enhanced efficiencies for phytoextraction and phytovolatilization. For example, metal-hyperaccumulating plants and microbes with unique abilities to tolerate, accumulate, and detoxify metals and metalloids represent an important reservoir of unique genes that could be transferred to fast-growing plant species for enhanced phytoremediation. There is also a need to develop new strategies to improve the acceptability of using genetically engineered plants for phytoremediation.
Weeding with transgenes.
Transgenes promise to reduce insecticide and fungicide use but relatively little has been done to significantly reduce herbicide use through genetic engineering. Recently, three strategies for transgene utilization have been developed that have the potential to change this. These are the improvement of weed-specific biocontrol agents, enhancement of crop competition or allelopathic traits, and production of cover crops that will self-destruct near the time of planting. Failsafe risk mitigation technologies are needed for most of these strategies.
Significance of microbial interactions in control of microbial ecosystems.
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Genetically modified organisms: an analysis of the regulatory framework currently employed within the European Union.
BACKGROUND: Genetic engineering technology is starting to bring many commercial products to the market. These genetically modified organisms (GMOs) and their derived products are subject to topical debate as to their benefits and risks. The strengths and weaknesses of the regulatory framework that controls their development and application is central to the question of whether this technology poses significant risk to the public health during this critical phase of its evolution. METHODS: A critical review was carried out of the legal framework regulating the contained use, deliberate release and some aspects of consumer protection relevant to the control of GMOs in Europe and the United Kingdom. RESULTS: The current legal framework is failing to provide a speed of adaptation commensurate with the development of the science of genetic engineering; failing to properly respond to democratic control; failing to resolve significant conflict between the protection of free markets and protection of public health and the environment; and failing to implement obligations on biodiversity. CONCLUSION: The present legal framework must be replaced. Current European Union proposals for new standards of regulation are welcome, but provide only for further incremental change, and do not address some significant fundamental flaws in our current laws.
Enzyme-catalyzed dehalogenation of pentachloroethane: why F87W-cytochrome P450cam is faster than wild type.
Under anaerobic conditions, cytochromes P450 can reductively dehalogenate heavily halogenated hydrocarbons, such as one- and two-carbon organic solvents. This catalytic capacity has drawn attention to the potential use of engineered forms of P450s in the remediation of contaminated deep subsurface ecosystems. Loida (1994, PhD Thesis, University of Illinois at Urbana-Champaign, IL) and S.G. Sligar (personal communication) have observed recently that an active-site variant of cytochrome P450cam (F87W) dechlorinates pentachloroethane approximately three times faster than the wild-type enzyme. Molecular dynamics simulations have revealed that the mutant enzyme binding pocket remains smaller, and that pentachloroethane assumes configurations closer to the heme-Fe in the F87W mutant twice as often as in the wild-type enzyme. This result is consistent with a collisional model of dehalogenation, which agrees with experimental observations [Li and Wackett (1993) Biochemistry, 32, 9355-9361] that solutions containing wild-type P450cam dehalogenate pentachloroethane 100 times faster than those containing free heme. The simulations suggest that it is unlikely that Trp87 significantly stabilizes the developing negative charge on the substrate during carbon-halogen bond reduction. The design of improved microbial enzymes that incorporate both steric and electronic effects continues for use in remediating halogenated contaminants in situ.
[Biological life support systems: investigations on board of orbital complex "Mir"].
From 1989 till 1998 twelve experiments were performed by Bulgarian, Russian, Slovak, and US researchers and engineers on the effects of space flight on the model of ecosystem "algae-fishes-bacteria", and ontogenesis of birds (Japanese quail) and higher plants. For the first time several viable chicks were hatched and passed the whole cycle of their embryonic development in the MIR microgravity. The length of the plant ontogenetic cycle as a whole and its specific stages appeared to be same as on Earth. Seeds of Brassica rapa gathered and planted in greenhouse Svet on board MIR yielded robust shoots. Photosynthesis and dark respiration of plants growing in spaceflight were successfully measured.
Spread of organisms with novel genotypes: thoughts from an ecological perspective.
One category of objection to the release of organisms produced by genetic engineering is based on the fear that such organisms may persist in the environment and damage existing ecosystems. An assessment of environmental risk thus involves an ecological question analogous to the introduction of exotic species which has been known to produce serious ecological disruptions. An investigation of the literature on exotic introductions reveals, however, that foreign species do not invariably produce adverse changes. Ecologists believe that only a fraction of immigrating species actually produces ecological dislocation while the majority probably fail to penetrate existing biotic assemblages. Stressed or simplified environments are, however, more vulnerable to successful invasion. Unfortunately, because very little information has ever been collected to document the number or causes of failed introductions, it is impossible to quantify the probability that any introduced species will or will not cause serious disturbance purely on the basis of historical evidence. The development and spread of genotypes that confer resistance to chemical control agents in insects and microorganisms is also analogous to genetic engineering in that human activity contributes to the spread of new genotypes. In both groups of organisms, resistant genotypes can come to predominate in even geographically widespread populations with great rapidity. Resistance to pesticides in insects is usually found to be determined by single genes. In bacteria, antibiotic resistance genes are usually, if not always, associated with the extrachromosomal genetic elements known as plasmids. Bacteria seem to be able to transmit plasmid-borne genes between species and genera with facility. The ease with which new genes can be inserted into bacteria via plasmid vectors in recombinant technology is thus a two-edged sword. It may be very difficult to keep inserted genes isolated in single bacterial strains. The evaluation of the literature on which this report is based suggests that an ecological approach for risk assessment is appropriate. Microorganisms, for which genetic engineering is of most immediate importance, exhibit the same ecological properties as higher organisms. The proportion of an organism's genome which is novel has no direct correlation with the magnitude of impact such a change may have in economic, medical, or ecological terms. Meaningful probabilities for persistence of engineered organisms in the environment will have to be generated by experiment, probably with model microbial ecosystems.
Recombinant plasmid mobilization between E. coli strains in seven sterile microcosms.
Transfer by mobilization of a pBR derivative recombinant plasmid lacking transfer functions (oriT+, tra-, mob-) from one E. coli K12 strain to another was investigated in seven sterile microcosms corresponding to different environments. These microcosms were chosen as representative of environments that genetically engineered microorganisms (GEMOs) encounter after accidental release, namely attached biomass in aquatic environments (biofilm), soil, seawater, freshwater, wastewater, mouse gut, and mussel gut, GEMOs survived in the same way as the host strains in all microcosms. Recombinant DNA mobilization occurred in the mouse gut, in sterile soil, and in biofilm. The plasmid transfer rates principally reflected the environmental conditions encountered in each microcosm.