Containment of genetically modified (GM) microorganisms such as Escherichia coli is a legal requirement to protect the environment from an unintended release and to avoid horizontal gene transfer (HGT) of recombinant DNA to native bacteria. In this study, we sampled the laboratory wastewater (LWW) at a large Swiss university from three sources over 2 years and cultured ampicillin-resistant, presumptive GM E. coli. From a total of 285 samples, 127 contained presumptive GM E. coli (45%) at a mean concentration of 2.8 × 102 CFU/ml. Plasmid DNA of 11 unique clones was partially or entirely sequenced. All consisted of cloning vectors harboring research-specific inserts. To estimate the chance of HGT between GM E. coli and native bacteria in LWW, we identified taxa representative for the bacterial community in LWW using 16S rRNA amplicon sequencing and measured conjugation frequencies of E. coli with five LWW isolates. At optimal conjugation conditions, frequencies were between 3.4 × 10−3 and 2.4 × 10−5. Given the absence of transferable broad-host range plasmids and suboptimal conjugation conditions in the LWW system, we conclude that the chance of HGT is relatively low. Still, this study shows that the implementation of robust containment measures is key to avoid the escape of GM microorganisms.
This work is first intended to optimize the experimental conditions for the maximum degradation of guaiacol (2-methoxyphenol)
by Fenton’s reagent, and second, to improve the process efficiency through the use of solar radiation. Guaiacol is considered
as a model compound of pulp and paper mill effluent. The experiments were carried out in a laboratory-scale reactor subjected
or not to solar radiation. Hydrogen peroxide solution was continuously introduced into the reactor at a constant flow rate.
The kinetics of organic matter decay was evaluated by means of the chemical oxygen demand (COD) and the absorbance measurements.
The experimental results showed that the Fenton and solar photo-Fenton systems lead successfully to 90% elimination of COD
and absorbance at 604 nm from a guaiacol solution under particular experimental conditions. The COD removal always obeyed
a pseudo-first-order kinetics. The effect of pH, temperature, H2O2 dosing rate, initial concentration of Fe2+, and initial COD was investigated using the Fenton process. The solar photo-Fenton system needed less time and consequently
less quantity of H2O2. Under the optimum experimental conditions, the solar photo-Fenton process needs a dose of H2O2 40% lower than that used in the Fenton process to remove 90% of COD. 相似文献
Short chain chlorinated paraffins (SCCPs) are a group of persistent organic pollutants (POPs) of increasing concern, but are to date not widely investigated in the environment, largely due to the challenges involved in their quantification. Here, SCCPs were quantified in marine sediments from the Firth of Clyde, Scotland, by gas chromatography with electron capture negative ionisation mass spectrometry (GC-ECNIMS) and through carbon skeleton analysis by gas chromatography with flame ionisation detection (GC-FID), and the analytical challenges encountered are discussed. Concentrations in the sediments ranged from 0.4 to 69 μg kg−1 when determined by GC-ECNIMS, and from 5.6 to 379 μg kg−1 when determined by GC-FID. For 8 out of 11 samples, analysis by GC-FID gave higher results than analysis by GC-ECNIMS. Unexpected aspects of the analysis, such as the presence of high concentrations of longer chain chlorinated paraffins in the samples, are also presented. 相似文献
Six groups of rats (n?=?10 per group) were exposed to 1 and 10 mg/l of sodium arsenate for 45 and 90 days. Kidneys from treated groups exposed to arsenic showed higher levels of trans isomers of oleic and linoleic acids as trans C181n-9, trans C18:1n-11, and trans C18:2n-6 isomers. However, a significant decrease in eicosenoic (C20:1n-9) and arachidonic (C20:4n-6) acids were observed in treated rats. Moreover, the “Δ5 desaturase index” and the saturated/polyunsaturated fatty acids ratio were increased. There was a significant increase in the level of malondialdehyde at 10 mg/l of treatment and in the amount of conjugated dienes after 90 days (p?0.05). Significant kidney damage was observed at 10 mg/l by increase of plasma marker enzymes. Histological studies on the ultrastructure changes of kidney supported the toxic effect of arsenate exposure. Arsenate intoxication activates significantly the superoxide dismutase at 10 mg/l for 90 days, whereas the catalase activity was markedly inhibited in all treated groups (p?0.05). In addition, glutathione peroxidase activity was significantly increased at 45 days and dramatically declined after 90 days at 10 mg/l (p?0.05). A significant increase in the level of glutathione was marked for the groups treated for 45 and 90 days at 1 mg/l followed by a significant decrease for rats exposed to 10 mg/l for 90 days. An increase in the level of protein carbonyl was observed in all treated groups (p?0.05). In conclusion, the present study provides evidence for a direct effect of arsenate on fatty acid (FA) metabolism which concerns the synthesis pathway of n-6 polyunsaturated fatty acids and leads to an increase in the trans FAs isomers. Therefore, FA-induced arsenate kidney damage could contribute to trigger kidney cancer. 相似文献
Structurally complex landscapes may enhance local species richness and interactions, which is possibly due to a higher species pool in complex landscapes. This hypothesis was tested using cereal aphid parasitoids (Hymenoptera, Aphidiidae) by comparing 12 winter wheat fields in structurally complex landscapes (>50% semi-natural habitats; n = 6) and structurally simple landscapes dominated by agricultural lands (>80% arable land; n = 6). Surprisingly, landscape structural complexity had no effect on aphid parasitoid species diversity. In complex landscapes 12 and in simple landscapes 11 species were found; 9 species occurred in both landscape types. Hence, arable fields in high-intensity agricultural landscapes with little non-crop area can support a similar diversity of cereal aphid parasitoids as structurally complex landscapes. This finding suggests that cereal aphid parasitoids may find necessary resources even in simple landscapes, making generalisations concerning the relationship between landscape composition and biodiversity in arable fields difficult. 相似文献
Summary The research addressed two questions: (1) doIguana iguana hatchlings recognize their kin, and (2) what are the recognition mechanisms? Eggs were collected from wild and captive-raised
females and hatched in semi-natural incubators. In the first experiment we used eggs from two females. One of the clutches
was subdivided to be placed in different incubators. Immediately after emergence one of these hatchling groups was introduced
into a 10 m x 10 m enclosure. At the same time we introduced hatchlings from another female. The remaining hatchling group
was kept separate for 3 weeks and was then introduced into the same cage. Unrelated hatchlings separated from each other.
Related but separated hatchlings grouped according to introduction date. In the second experiment we maintained eight kin
groups in individual cages and two hatchlings per kin group in an additonal cage. Hatchlings from the mixed group showed no
preference for their kin before physical contact with pure kin groups had occurred. After physical contact hatchling recognized
their kin by feces smell. Body odor is likely to be also involved. 相似文献
Environmental Modeling & Assessment - Costa Rica has set a very ambitious Nationally Determined Contribution (NDC). Despite the low-carbon footprint of its power sector, the goal set in its NDC... 相似文献
The risk assessment of genetically-modified plants pursuant to Annex II B of EU Directive 94/15/EC assumes that it is possible
to infer the environmental impacts of a crop plant from its characteristics, so most of Annex II should also be applicable
to conventional plants. To test this, we surveyed reports on the ecological impacts of the cultivation of non-transgenic crop
plants with novel or improved traits and, in three cases, investigated whether Annex II B would have been adequate to indicate
the effects. Such an assessment appears to be feasible only if the time frame on which it is based is short, so that long-term
effects cannot be assessed. Secondly, the plant must be genetically homogenous which is not always granted, e.g. with forest-trees.
Thirdly, the cultivation area must be defined. Differences in the behaviour of foreign plants between their original and cultivation
habitats may be ecologically relevant and should be assessed. In the (few) cases where direct inference of the observed effects
was possible from inherent traits, these effects often correlated with poor adaptation to local environmental conditions.
The ecological impacts of traits that had been introduced in order to overcome poor adaptation may differ widely according
to the way in which the traits are exploited. In practice, the effects of agricultural measures are more important than the
effects of gene transfer and invasiveness, although the latter currently play a major role in risk assessment. In the light
of these deliberations, a modification of Annex II B of EU Directive 94/15/EC is suggested. 相似文献
This work summarizes the results of a study of atmospheric wet and dry deposition fluxes of Deisopropyl-atrazine (DEA), Desethyl-atrazine (DET), Atrazine, Terbuthylazine, Alachlor, Metolachlor, Diflufenican, Fenoxaprop-p-ethyl, Iprodione, Isoproturon and Cymoxanil pesticides conducted in Strasbourg, France, from August 2000 through August 2001. The primary objective of this work was to calculate the total atmospheric pesticide deposition fluxes induced by atmospheric particles. To do this, a modified one-dimensional cloud water deposition model was used. All precipitation and deposition samples were collected at an urban forested park environment setting away from any direct point pesticide sources. The obtained deposition fluxes induced by atmospheric particles over a forested area showed that the dry deposition flux strongly contributes to the total deposition flux. The dry particle deposition fluxes are shown to contribute from 4% (DET) to 60% (cymoxanil) to the total deposition flux (wet + dry). 相似文献