Cry1Ab protein from Bt transgenic rice does not residue in rhizosphere soil

Expression of Cry1Ab protein in Bt transgenic rice (KMD) and its residue in the rhizosphere soil during the whole growth in field, as well as degradation of the protein from KMD straw in five soils under laboratory incubation were studied. The residue of Cry1Ab protein in KMD rhizosphere soil was undetectable (below the limit of 0.5 ng/g air-dried soil). The Cry1Ab protein contents in the shoot and root of KMD were 3.23-8.22 and 0.68-0.89 microg/g (fresh weight), respectively. The half-lives of the Cry1Ab protein in the soils amended with KMD straw (4%, w/w) ranged from 11.5 to 34.3d. The residence time of the protein varied significantly in a Fluvio-marine yellow loamy soil amended with KMD straw at the rate of 3, 4 and 7%, with half-lives of 9.9, 13.8 and 18d, respectively. In addition, an extraction method for Cry1Ab protein in soil was developed, with extraction efficiencies of 46.4-82.3%.     

The impact of Bt maize expressing the Cry1Ac protein on non-target arthropods

Environmental Science and Pollution Research - From 2014 to 2016, individuals of the principal non-target arthropod (NTA) species in a field of Bt maize expressing the Cry1Ac protein (Bt38) were...     

Fate of Bacillus thuringiensis (Bt) Cry3Bb1 protein in a soil microcosm

Transgenic crops expressing insecticidal, crystalline (Cry) Bacillus thuringiensis (Bt) proteins were commercialized in the US in 1996. There is little information in the peer-reviewed literature on the environmental fate of the coleopteran-active Bt Cry3Bb1 protein expressed in event MON863 corn. The exposure characterization of Bt proteins is unique in that the fate of the protein in soil and in crop residue must be considered. To date, the significance of macrodecomposing organisms, such as earthworms, isopods, and springtails, to the dissipation of Bt proteins present in crop residue has not been assessed. In addition, the input of Bt proteins into soil through leaching from post-harvest crop residue has not been examined. Two laboratory microcosm studies were conducted to determine the fate of Bt Cry3Bb1 in decomposing MON863 corn residue and to determine whether Bt proteins can enter soil by leaching from crop residue. In addition, the importance of macrodecomposing organisms to the degradation of Bt proteins in corn residue was assessed. Laboratory microcosms containing MON863 corn leaf, root, and stalk with and without macrodecomposers were used to examine the fate of Bt Cry3Bb1 in post-harvest MON863 corn residue. A half-life of less than five days was found for Bt Cry3Bb1 protein in decomposing MON863 corn residue. There was a trend of increasing half-life of Cry3Bb1 in microcosms containing macrodecomposers, however, this trend was only significant (p<0.05) for Bt Cry3Bb1 in MON863 leaf tissue and this increase is not likely relevant for non-target exposure. The recovery of Bt Cry3Bb1 protein from soil extracts was either below the limit of quantification (9 ng g(-1) soil) or below the limit of detection (0.7 ng mL(-1)) at all time points during the study. Based on the results from this study, Bt protein leaching from post-harvest crop residue is not a significant contributor to Bt protein input into soil.     

Impact of electrokinetic remediation on microbial communities within PCP contaminated soil

Electrokinetic techniques have been used to stimulate the removal of organic pollutants within soil, by directing contaminant migration to where remediation may be more easily achieved. The effect of this and other physical remediation techniques on the health of soil microbial communities has been poorly studied and indeed, largely ignored. This study reports the impact on soil microbial communities during the application of an electric field within ex situ laboratory soil microcosms contaminated with pentachlorophenol (PCP; 100mg kg(-1) oven dry soil). Electrokinetics reduced counts of culturable bacteria and fungi, soil microbial respiration and carbon substrate utilisation, especially close to the acidic anode where PCP accumulated (36d), perhaps exacerbated by the greater toxicity of PCP at lower soil pH. There is little doubt that a better awareness of the interactions between soil electrokinetic processes and microbial communities is key to improving the efficacy and sustainability of this remediation strategy.     

Interactions between plant and rhizosphere microbial communities in a metalliferous soil

In the present work, the relationships between plant consortia, consisting of 1-4 metallicolous pseudometallophytes with different metal-tolerance strategies (Thlaspi caerulescens: hyperaccumulator; Jasione montana: accumulator; Rumex acetosa: indicator; Festuca rubra: excluder), and their rhizosphere microbial communities were studied in a mine soil polluted with high levels of Cd, Pb and Zn. Physiological response and phytoremediation potential of the studied pseudometallophytes were also investigated. The studied metallicolous populations are tolerant to metal pollution and offer potential for the development of phytoextraction and phytostabilization technologies. T. caerulescens appears very tolerant to metal stress and most suitable for metal phytoextraction; the other three species enhance soil functionality. Soil microbial properties had a stronger effect on plant biomass rather than the other way around (35.2% versus 14.9%). An ecological understanding of how contaminants, ecosystem functions and biological communities interact in the long-term is needed for proper management of these fragile metalliferous ecosystems.     

The impact of zero-valent iron nanoparticles upon soil microbial communities is context dependent

Nanosized zero-valent iron (nZVI) is an effective land remediation tool, but there remains little information regarding its impact upon and interactions with the soil microbial community. nZVI stabilised with sodium carboxymethyl cellulose was applied to soils of three contrasting textures and organic matter contents to determine impacts on soil microbial biomass, phenotypic (phospholipid fatty acid (PLFA)), and functional (multiple substrate-induced respiration (MSIR)) profiles. The nZVI significantly reduced microbial biomass by 29 % but only where soil was amended with 5 % straw. Effects of nZVI on MSIR profiles were only evident in the clay soils and were independent of organic matter content. PLFA profiling indicated that the soil microbial community structure in sandy soils were apparently the most, and clay soils the least, vulnerable to nZVI suggesting a protective effect imparted by clays. Evidence of nZVI bactericidal effects on Gram-negative bacteria and a potential reduction of arbuscular mycorrhizal fungi are presented. Data imply that the impact of nZVI on soil microbial communities is dependent on organic matter content and soil mineral type. Thereby, evaluations of nZVI toxicity on soil microbial communities should consider context. The reduction of AM fungi following nZVI application may have implications for land remediation.     

Biotransformation of atrazine and metolachlor within soil profile and changes in microbial communities

Biotransformation studies of atrazine, metolachlor and evolution of their metabolites were carried out in soils and subsoils of Northern Greece. Trace atrazine, its metabolites and metolachlor residues were detected in field soil samples 1 year after their application. The biotransformation rates of atrazine were higher in soils and subsoils of field previously exposed to atrazine (maize field sites) than in respective layers of the field margin. The DT₅₀ values of atrazine ranged from 5 to 18 d in the surface layers of the adapted soils. DT₅₀ values of atrazine increased as the soil depth increased reaching the value of 43 d in the 80-110 cm depth layer of adapted soils. Metolachlor degraded at slower rates than atrazine in surface soils, subsoils of field and field margins with the respective DT₅₀ values ranging from 56 to 72 d in surface soils and from 165 to 186 d in subsoils. Hydroxyatrazine was the most frequently detected metabolite of atrazine. The maximum concentrations of metolachlor-OXA and metolachlor-ESA were detected in the soil layers of 20-40 cm depth after 90 d of incubation. Principal Component Analysis (PCA) of soil Phospholipid Fatty Acids (PLFAs), fungal/bacterial and Gram-negative/Gram-positive ratios of the PLFA profiles revealed that the higher biotransformation rates of atrazine were simultaneously observed with the abundance of Gram-negative bacteria while the respective rates of metolachlor were observed in soil samples with abundance of fungi.     

Microbial degradation and impact of Bracken toxin ptaquiloside on microbial communities in soil

The carcinogenic and toxic ptaquiloside (PTA) is a major secondary metabolite in Bracken fern (Pteridium aquilinum (L.) Kuhn) and was hypothesized to influence microbial communities in soil below Bracken stands. Soil and Bracken tissue were sampled at field sites in Denmark (DK) and New Zealand (NZ). PTA contents of 2.1 +/- 0.5 mg g(-1) and 37.0 +/- 8.7 mg g(-1) tissue were measured in Bracken fronds from DK and NZ, respectively. In the two soils the PTA levels were similar (0-5 microg g(-1) soil); a decrease with depth could be discerned in the deeper B and C horizons of the DK soil (weak acid sandy Spodosol), but not in the NZ soil (weak acid loamy Entisol). In the DK soil PTA turnover was predominantly due to microbial degradation (biodegradation); chemical hydrolysis was occurring mainly in the uppermost A horizon where pH was very low (3.4). Microbial activity (basal respiration) and growth ([3H]leucine incorporation assay) increased after PTA exposure, indicating that the Bracken toxin served as a C substrate for the organotrophic microorganisms. On the other hand, there was no apparent impact of PTA on community size as measured by substrate-induced respiration or composition as indicated by community-level physiological profiles. Our results demonstrate that PTA stimulates microbial activity and that microorganisms play a predominant role for rapid PTA degradation in Bracken-impacted soils.     

Biotransformation of atrazine and metolachlor within soil profile and changes in microbial communities

Biotransformation studies of atrazine, metolachlor and evolution of their metabolites were carried out in soils and subsoils of Northern Greece. Trace atrazine, its metabolites and metolachlor residues were detected in field soil samples 1 year after their application. The biotransformation rates of atrazine were higher in soils and subsoils of field previously exposed to atrazine (maize field sites) than in respective layers of the field margin. The DT₅₀ values of atrazine ranged from 5 to 18 d in the surface layers of the adapted soils. DT₅₀ values of atrazine increased as the soil depth increased reaching the value of 43 d in the 80–110 cm depth layer of adapted soils. Metolachlor degraded at slower rates than atrazine in surface soils, subsoils of field and field margins with the respective DT₅₀ values ranging from 56 to 72 d in surface soils and from 165 to 186 d in subsoils. Hydroxyatrazine was the most frequently detected metabolite of atrazine. The maximum concentrations of metolachlor-OXA and metolachlor-ESA were detected in the soil layers of 20–40 cm depth after 90 d of incubation. Principal Component Analysis (PCA) of soil Phospholipid Fatty Acids (PLFAs), fungal/bacterial and Gram-negative/Gram-positive ratios of the PLFA profiles revealed that the higher biotransformation rates of atrazine were simultaneously observed with the abundance of Gram-negative bacteria while the respective rates of metolachlor were observed in soil samples with abundance of fungi.     

Phosphate-modified ferric-based material remediates lead and arsenic co-contaminated soil and enhances maize seedling growth

Environmental Science and Pollution Research - Soil heavy metal pollution, especially lead (Pb) and arsenic (As), is a global issue that requires urgent attention. In the present study,...     

In-field variation in 2,4-D mineralization in relation to sorption and soil microbial communities

This study was undertaken to assess 2,4-D mineralization in an undulating cultivated field, along a sloping transect (458 m to 442 m above sea level), as a function of soil type, soil microbial communities and the sorption of 2,4-D to soil. The 2,4-D soil sorption coefficient (Kd) ranged from 1.81 to 4.28 L kg(-1), the 2,4-D first-order mineralization rate constant (k) ranged from 0.04 to 0.13 day(-1) and the total amount of 2,4-D mineralized at 130 days (M(130)) ranged from 24 to 39%. Both k and M(130) were significantly negatively associated (or correlated) with soil organic carbon content (SOC) and Kd. Both k and M(130) were significantly associated with two fatty-acid methyl esters (FAME), i17:1 and a18, but not with twenty-two other individual FAME. Imperfectly drained soils (Gleyed Dark Grey Chernozems) in lower-slopes showed significantly lesser 2,4-D mineralization relative to well-drained soils (Orthic Dark Grey Chernozems) in mid- and upper-slopes. Well-drained soils had a greater potential for 2,4-D mineralization because of greater abundance and diversity of the microbial community in these soils. However, the reduced 2,4-D mineralization in imperfectly drained soils was predominantly because of their greater SOC and increased 2,4-D sorption, limiting the bioavailability of 2,4-D for degradation. The wide range of 2,4-D sorption and mineralization in this undulating cultivated field is comparable in magnitude and extent to the variability of 2,4-D sorption and mineralization observed at a regional scale in Manitoba. As such, in-field variations in SOC and the abundance and diversity of microbial communities are determining factors that require greater attention in assessing the risk of movement of 2,4-D by runoff, eroded soil and leaching.     

In-field variation in 2,4-D mineralization in relation to sorption and soil microbial communities

This study was undertaken to assess 2,4-D mineralization in an undulating cultivated field, along a sloping transect (458 m to 442 m above sea level), as a function of soil type, soil microbial communities and the sorption of 2,4-D to soil. The 2,4-D soil sorption coefficient (Kd) ranged from 1.81 to 4.28 L kg^?1, the 2,4-D first-order mineralization rate constant (k) ranged from 0.04 to 0.13 day^?1 and the total amount of 2,4-D mineralized at 130 days (M₁₃₀) ranged from 24 to 39%. Both k and M₁₃₀ were significantly negatively associated (or correlated) with soil organic carbon content (SOC) and Kd. Both k and M₁₃₀ were significantly associated with two fatty-acid methyl esters (FAME), i17:1 and a18, but not with twenty-two other individual FAME. Imperfectly drained soils (Gleyed Dark Grey Chernozems) in lower-slopes showed significantly lesser 2,4-D mineralization relative to well-drained soils (Orthic Dark Grey Chernozems) in mid- and upper-slopes. Well-drained soils had a greater potential for 2,4-D mineralization because of greater abundance and diversity of the microbial community in these soils. However, the reduced 2,4-D mineralization in imperfectly drained soils was predominantly because of their greater SOC and increased 2,4-D sorption, limiting the bioavailability of 2,4-D for degradation. The wide range of 2,4-D sorption and mineralization in this undulating cultivated field is comparable in magnitude and extent to the variability of 2,4-D sorption and mineralization observed at a regional scale in Manitoba. As such, in-field variations in SOC and the abundance and diversity of microbial communities are determining factors that require greater attention in assessing the risk of movement of 2,4-D by runoff, eroded soil and leaching.     

Effects of lead and cadmium nitrate on biomass and substrate utilization pattern of soil microbial communities

A study was conducted to evaluate the effects of different concentrations of lead (Pb) and cadmium (Cd) applied as their nitrates on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), and substrate utilization pattern of soil microbial communities. The C(mic) and N(mic) contents were determined at 0, 14, 28, 42 and 56 days after heavy metal application (DAA). The results showed a significant decline in the C(mic) for all Pb and Cd amended soils from the start to 28 DAA. From 28 to 56 DAA, C(mic) contents changed non-significantly for all other treatments except for 600 mgkg(-1) Pb and 100 mgkg(-1) Cd in which it declined significantly from 42 to 56 DAA. The N(mic) contents also decreased significantly from start to 28 DAA for all other Pb and Cd treatments except for 200 mgkg(-1) Pb which did not show significant difference from the control. Control and 200 mgkg(-1) Pb had significantly lower soil microbial biomass C:N ratio as compared with other Pb treatments from 14 to 42 DAA, however at 56 DAA, only 1000 mgkg(-1) Pb showed significantly higher C:N ratio compared with other treatments. No significant difference in C:N ratio for all Cd treated soils was seen from start to 28 DAA, however from 42 to 56 DAA, 100 mgkg(-1) Pb showed significantly higher C:N ratio compared with other treatments. On 56 DAA, substrate utilization pattern of soil microbial communities was determined by inoculating Biolog ECO plates. The results indicated that Pb and Cd addition inhibited the functional activity of soil microbial communities as indicated by the intensity of average well color development (AWCD) during 168 h of incubation. Multivariate analysis of sole carbon source utilization pattern demonstrated that higher levels of heavy metal application had significantly affected soil microbial community structure.     

Extractable soil lipids and microbial activity as affected by Bt and non Bt maize grown on a silty clay loam soil

Pyrolysis-gas (Py-GC) chromatography was used to characterize extractable lipids from Bt and non-Bt maize shoots and soils collected at time of harvesting. Py-GC-MS (mass spectrometry) showed that the concentrations of total alkenes identified in non-Bt shoots and soils were 47.9 and 21.3% higher than in Bt maize shoots and soils, respectively. N-alkanes identified were of similar orders of magnitude in Bt and non-Bt maize shoots, but were 28.6% higher in Bt than in non-Bt soils. Bt maize shoots contained 29.7% more n-fatty acids than non-Bt maize shoots, whereas the concentrations of n-fatty acids in Bt soils were twice as high as those in non-Bt soils. Concentrations of unsaturated fatty acids in Bt maize shoots were 22.1% higher than those in non-Bt maize shoots, while concentrations of unsaturated fatty acids were 22.5% higher in non-Bt than in Bt soils. The cumulative CO2-C evolved from soils under Bt and non-Bt crops was 30.5% lower under Bt as compared to non-Bt crops, whereas when maize shoots were added to Bt and non-Bt soils, the decrease in CO2-C evolved were 16.5 and 23.6%, respectively. Our data showed that the cultivation of Bt maize significantly increased the saturated to unsaturated lipid ratios in soils which appeared to negatively affect microbial activity.     

Assessment of natural sepiolite on cadmium stabilization, microbial communities, and enzyme activities in acidic soil

A pot trial was conducted to assess the efficiency of sepiolite-induced cadmium (Cd) immobilization in ultisoils. Under Cd concentrations of 1.25, 2.5, and 5 mg?kg^?1, the available Cd in the soil after the application of 1–10 % sepiolite decreased by a maximum of 44.4, 23.0, and 17.0 %, respectively, compared with no sepiolite treatments. The increase in the values of soil enzyme activities and microbial number proved that a certain metabolic recovery occurred after sepiolite treatment. The dry biomass of spinach (Spinacia oleracea) increased with increasing sepiolite concentration in the soil. However, the concentration (dry weight) of Cd in the spinach shoots decreased with the increase in sepiolite dose, with maximum reduction of 92.2, 90.0, and 84.9 %, respectively, compared with that of unamended soils. Under a Cd level of 1.25 mg?kg^?1, the Cd concentration in the edible parts of spinach at 1 % sepiolite amendment was lower than 0.2 mg?kg^?1 fresh weight, the maximum permissible concentration (MPC) of Cd in vegetable. Even at higher Cd concentrations (2.5 and 5 mg?kg^?1), safe spinach was produced when the sepiolite treatment was up to 5 %. The results showed that sepiolite-assisted remediation could potentially succeed on a field scale by decreasing Cd entry into the food chain.     

Monoterpenes and microbial metabolites in the soil

Volatile microbial metabolites were analysed in the soil beneath 15 H year-old Picea abies which had been fumigated for 5 consecutive years with charcoal-filtered air enriched with ozone and sulphur dioxide. Major compounds which could be attributed to the metabolism of basidiomycete fungi were oct-1-en-3-ol, oct-1-en-3-one and 1,3-octadiene. They were accompanied by other C(8)-compounds. The lower amounts of C(8)-compounds observed in the soil of the sulphur dioxide and ozone treatment chambers indicate a reduced development of basidiomycetes. The higher amounts of geosmin and 2-methylisoborneol found in the soil of the ozone treatment chamber indicate an increase in actinomycete populations. The differences of the monoterpene patterns in the particular soils were not large enough to recognize trends unequivocally.     

Transgenic poplar trees expressing yeast cadmium factor 1 exhibit the characteristics necessary for the phytoremediation of mine tailing soil

Genetic engineering of plants for phytoremediation is thought to be possible based on results using model plants expressing genes involved in heavy metal resistance, which improve the plant’s tolerance of heavy metals and accumulation capacity. The next step of progress in this technology requires the genetic engineering of plants that produce large amounts of biomass and the testing of these transgenic plants in contaminated soils. Thus, we transformed a sterile line of poplar Populus alba X P. tremula var. glandulosa with a heavy metal resistance gene, ScYCF1 (yeast cadmium factor 1), which encodes a transporter that sequesters toxic metal(loid)s into the vacuoles of budding yeast, and tested these transgenic plants in soil taken from a closed mine site contaminated with multiple toxic metal(loid)s under greenhouse and field conditions. The YCF1-expressing transgenic poplar plants exhibited enhanced growth, reduced toxicity symptoms, and increased Cd content in the aerial tissue compared to the non-transgenic plants. Furthermore, the plants accumulated increased amounts of Cd, Zn, and Pb in the root, because they could establish an extensive root system in mine tailing soil. These results suggest that the generation of YCF1-expressing transgenic poplar represents the first step towards producing plants for phytoremediation. The YCF1-expressing poplar may be useful for phytostabilization and phytoattenuation, especially in highly contaminated regions, where wild-type plants cannot survive.     

Effect of tetraconazole application on the soil microbial community

Tetraconazole is one of the most commonly used triazole fungicides in agricultural practice, and its continuous application poses a potential risk for non-target soil microorganisms. Therefore, the objective of this study was to evaluate the effect of tetraconazole at the field rate (T1, 0.33 mgkg^?1 of soil), three times the field rate (T3, 1.00 mgkg^?1 of soil) and 10 times the field rate (T10, 3.33 mgkg^?1 of soil) on the soil microorganisms. To ascertain this effect, the tetraconazole concentration and the microbial properties with potential as bioindicators of soil health (i.e. microbial biomass C, basal respiration, substrate-induced respiration, structure diversity and functional community profiling) were determined. The results showed that the degradation half-lives of tetraconazole varied from 69 to 87 days, depending on the three application concentrations. The microbial biomass C, basal respiration and substrate-induced respiration were inhibited, but they tended to recover at the end of the incubation when tetraconazole was applied at the recommended field rate. The ratios of the gram-negative to gram-positive (GN to GP) bacteria decreased, and the fungi to bacteria ratio increased after a temporal decrease on the seventh day. A principal component analysis of the PLFAs showed that tetraconazole application significantly shifted the microbial community structure on day 7. Different functional community profiles were observed, depending on the tetraconazole application rates. It was concluded that tetraconazole application decreases the soil microbial biomass and activity and changes the structures of the soil microbial community.     

The adaptations of the microbial communities of the savanna soil over a period of wildfire,after the first rains,and during the rainy season

Environmental Science and Pollution Research - Annually, the Cerrado ecosystem alternates between dry periods and long rainy seasons. During the dry season, severe forest fires occur, consuming a...