Genetic engineering and water.
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Active biological containment (ABC) systems have been designed to control at will the survival or death of a bacterial population. These systems are based on the use of a killing gene, e.g., a porin-inducing protein such as the one encoded by the Escherichia coli gef gene, and a regulatory circuit that controls expression of the killing gene in response to the presence or absence of environmental signals. An ABC system for recombinant microorganisms that degrade a model pollutant was designed on the basis of the Pseudomonas putida TOL plasmid meta-cleavage regulatory circuit. The system consists of a fusion of the Pm promoter to lacI, whose expression is controlled by XylS with 3-methylbenzoate, and a fusion of a synthetic P(lac) promoter to gef. In the presence of the model pollutant, bacterial cells survived and degraded the target compound, whereas in the absence of the aromatic carboxylic acid cell death was induced. The system had two main drawbacks: (i) the slow death of the bacterial cells in soil versus the fast killing rate in liquid cultures in laboratory assays, and (ii) the appearance of mutants, at a rate of about 10(-8) per cell and generation, that did not die after the pollutant had been exhausted. We reinforced the ABC system by including it in a Deltaasd P. putida background. A P. putida Deltaasd mutant is viable only in complex medium supplemented with diaminopimelic acid, methionine, lysine, and threonine. We constructed a P. putida Deltaasd strain, called MCR7, with a Pm::asd fusion in the host chromosome. This strain was viable in the presence of 3-methylbenzoate because synthesis of the essential metabolites was achieved through XylS-dependent induction. In the P. putida MCR7 strain, an ABC system (Pm::lacI, xylS, P(lac)::gef) was incorporated into the host chromosome to yield strain MCR8. The number of MCR8 mutants that escaped killing was below our detection limit (<10(-9) mutants per cell and generation). The MCR8 strain survived and colonized rhizosphere soil with 3-methylbenzoate at a level similar to that of the wild-type strain. However, it disappeared in less than 20 to 25 days in soils without the pollutant, whereas an asd(+), biologically contained counterpart such as P. putida CMC4 was still detectable in soils after 100 days.
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Rental products are often a large expense in healthcare institutions. Desert Samaritan Medical Center in Mesa, AZ, took a look at the equipment rental dollars being spent on air therapy beds to determine if a new approach could result in significant cost savings. They identified the potential purchase and in-house maintenance of air therapy devices as an opportunity to increase productivity and service levels while simultaneously reducing expenses. After conducting a thorough product evaluation of various products, the institution purchased four portable mattress replacement systems, four beds complete with air therapy, in-bed scales and dynamic blowers and continue to rent air-fluidized therapy beds on an as-needed basis. Duties for supplying, cleaning and maintaining the equipment were shared between Materials Management, Patient Transport, Environmental Services, Clinical Engineering and Plant Services and Nursing. The hospital has realized a $90,000 expense reduction as a result and improved patient outcomes.
This paper presents results of a collaborative trial study (IUPAC project No. 650/93/97) involving 29 laboratories in 13 countries applying a method for detecting genetically modified organisms (GMOs) in food. The method is based on using the polymerase chain reaction to determine the 35S promotor and the NOS terminator for detection of GMOs. reference materials were produced that were derived from genetically modified soy beans and maize. Correct identification of samples containing 2% GMOs is achievable for both soy beans and maize. For samples containing 0.5% genetically modified soy beans, analysis of the 35S promotor resulted also in a 100% correct classification. However, 3 false-negative results (out of 105 samples analyzed) were reported for analysis of the NOS terminator, which is due to the lower sensitivity of this method. Because of the bigger genomic DNA of maize, the probability of encountering false-negative results for samples containing 0.5% GMOs is greater for maize than for soy beans. For blank samples (0% GMO), only 2 false-positive results for soy beans and one for maize were reported. These results appeared as very weak signals and were most probably due to contamination of laboratory equipment.
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High-erucic acid (HEA) Brassica napus cultivars are regaining interest in industrial contexts. Erucic acid and its derivatives are important renewable raw materials utilized in the manufacture of plastic films, in the synthesis of Nylon 13,13, and in the lubricant and emollient industries. Theoretically, the highest level of erucic acid that can be achieved by means of classical breeding is 66 mol%; however, using new approaches on the basis of genetic engineering, it might be possible to develop a B. napus cultivar containing levels of erucic acid significantly above 66 mol% (>80 mol%). In an attempt to increase the amounts of very-long-chain fatty acids (VLCFAs), and erucic acid in particular, in Canadian HEA B. napus cultivars, we have focused on two targets using a transgenic approach. We examined both the role/function of the Arabidopsis thaliana FAE1 (fatty acid elongase) gene by expressing it under the control of the seed-specific napin promoter in B. napus germplasm with analysis of the changes in VLCFA content in the seed oil of transgenic lines, and the performance of the yeast SLC1-1 (sphingolipid compensation mutant) in B. napus cv. Hero transgenic progeny in the field. Here, we report analyses of the contents of 22:1, total VLCFAand oil in the seed oil, as well as seed yield of the field-grown FAE1 and SLC1-1 B. napus cv. Hero progeny.
Many conversations on genetic modification over the past few years have begun with the words 'I'm not a scientist, but...' They usually go on to say they do not follow the scientific detail, but it doesn't seem right to tamper with genes. The media and pressure groups have fuelled the fire with emotive terms like 'Frankenstein food', 'genetic pollution' and 'mutant crops'. There are important lessons here, which are as much about people and society as they are about science.
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The literatures on potential of genetic engineering in sugarcane, transformation method and its efficiency, effects of promoter and selectable marker on gene expression and on identification of transformant, and achievement of genetic engineering in sugarcane were reviewed. Directions of further research were also suggested.
A high performance liquid chromatographic method with ethylenediamine dynamically modified silica column and evaporative light-scattering detection (ELSD) was developed for the direct determination of trehalose in transgenic tobacco extracts. The separation column (Zorbax Rx-SIL, 4.6 mm i.d. x 250 mm, 5 microns, Hewlett-Packard, USA) modified by ethylenediamine and a guard column (Zorbax Rx-SIL, 4.6 mm i.d. x 12.5 mm, 5 microns) were used. The mobile phase was a mixture of acetonitrile-water(2.6:1, V/V) containing 0.03% ethylenediamine. Regression equations revealed the linear relationships (r = 0.996-0.999) between the concentrations and peak areas of carbohydrates detected by ELSD. The detection limits of ELSD (S/N = 3:1) were 10 mg/L, 20 mg/L, 10 mg/L and 10 mg/L for fructose, glucose, sucrose and trehalose, respectively.
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