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Daniel O. Onunga Anastasiah N. Ngigi Aggrey Osogo Francis Orata Zachary M. Getenga 《Journal of environmental science and health. Part. B》2013,48(6):387-397
Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) has been used within the Nzoia River Basin (NRB), especially in Bunyala Rice Irrigation Schemes, in Kenya for the control of pests. In this study, the capacity of native bacteria to degrade carbofuran in soils from NRB was investigated. A gram positive, rod-shaped bacteria capable of degrading carbofuran was isolated through liquid cultures with carbofuran as the only carbon and nitrogen source. The isolate degraded 98% of 100-μg mL?1 carbofuran within 10 days with the formation of carbofuran phenol as the only detectable metabolite. The degradation of carbofuran was followed by measuring its residues in liquid cultures using high performance liquid chromatography (HPLC). Physical and morphological characteristics as well as molecular characterization confirmed the bacterial isolate to be a member of Bacillus species. The results indicate that this strain of Bacillus sp. could be considered as Bacillus cereus or Bacillus thuringiensis with a bootstrap value of 100% similar to the 16S rRNA gene sequences. The biodegradation capability of the native strains in this study indicates that they have great potential for application in bioremediation of carbofuran-contaminated soil sites. 相似文献
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The phenylurea herbicide diuron [N-(3,4-dichlorophenyl)-N,N-dimethylurea] is widely used alone or in a broad range of herbicide formulations. Its degradation in sugarcane-cultivated soils which have been impacted by the herbicide through repeated applications was studied. Liquid culture experiments with diuron as the only carbon source led to the isolation of different bacterial strains capable of degrading diuron. The bacterial species belonging to the genera Bacillus, Vagococcus, and Burkholderia, identified through biochemical and molecular characterization, degraded diuron to different extents. The isolated Bacillus cereus, Vagococcus fluvialis, Burkholderia ambifaria, and Bacillus spp1 degraded diuron by 21%, 25%, 22%, and 19% of the initially applied concentration of 40?mg?L?1, respectively, after 35 days of incubation in liquid culture media. Small amounts of 3,4-dichloroaniline and the de-methylated metabolite N-(3,4-dichlorophenyl)-N-methylurea were detected in liquid culture media. The combination of V. fluvialis and B. ambifaria showed an enhanced degradation of up to 30% of the initially applied concentration of 40?mg?L?1. Degradation by pure isolates was low (18–25%) compared to the capacities of diuron degradation shown by the bacterial communities (58–74%). This study showed the presence of diuron degraders in sugarcane-cultivated soils impacted by diuron due to repeated applications. 相似文献
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Ngigi AN Getenga ZM Boga HI Ndalut PK 《Journal of environmental science and health. Part. B》2012,47(8):769-778
In this study soils from sugarcane-cultivated fields were screened for bacterial species capable of atrazine (6-chloro-N2-ethyl-N?-isopropyl-1,3,5-triazine-2,4-diamine) degradation due to long exposure of the soils to this herbicide. To enrich for atrazine degraders, Minimal Salt Medium containing atrazine as the sole N source and glucose as the C source was inoculated with soils impacted with this herbicide and incubated. Bacterial growth was monitored by measuring optical density. The degradation of atrazine was followed by measuring residual atrazine in liquid cultures over a given time period by high performance liquid chromatography. Bacterial strains isolated from the enrichment cultures were characterized by biochemical tests and identified by 16S rRNA gene sequencing. Two bacterial strains coded ISL 8 and ISL 15 isolated from two different fields were shown to have 94 and 96% 16S rRNA gene sequence similarity to Burkholderia cepacia respectively. Another bacterial sp., ISL 14 was closely related to Enterobacter cloacae with a 96% 16S rRNA gene sequence similarity. There was not much difference between the extents of atrazine degradation by the enrichment cultures with communities (79-82% applied amount) from which pure strains were isolated and the pure strains themselves in liquid cultures that showed a degradation of 53-83% of applied amount. The study showed existence of bacterial strains in different sugarcane-cultivated fields which can use atrazine as a nitrogen source. The bacterial strains isolated can be used to enhance the degradation of atrazine in contaminated soils where atrazine is still considered to be recalcitrant. 相似文献
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Anastasiah N. Ngigi Zachary M. Getenga Hamadi I. Boga Paul K. Ndalut 《Journal of environmental science and health. Part. B》2013,48(8):769-778
In this study soils from sugarcane-cultivated fields were screened for bacterial species capable of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) degradation due to long exposure of the soils to this herbicide. To enrich for atrazine degraders, Minimal Salt Medium containing atrazine as the sole N source and glucose as the C source was inoculated with soils impacted with this herbicide and incubated. Bacterial growth was monitored by measuring optical density. The degradation of atrazine was followed by measuring residual atrazine in liquid cultures over a given time period by high performance liquid chromatography. Bacterial strains isolated from the enrichment cultures were characterized by biochemical tests and identified by 16S rRNA gene sequencing. Two bacterial strains coded ISL 8 and ISL 15 isolated from two different fields were shown to have 94 and 96% 16S rRNA gene sequence similarity to Burkholderia cepacia respectively. Another bacterial sp., ISL 14 was closely related to Enterobacter cloacae with a 96% 16S rRNA gene sequence similarity. There was not much difference between the extents of atrazine degradation by the enrichment cultures with communities (79–82% applied amount) from which pure strains were isolated and the pure strains themselves in liquid cultures that showed a degradation of 53–83% of applied amount. The study showed existence of bacterial strains in different sugarcane-cultivated fields which can use atrazine as a nitrogen source. The bacterial strains isolated can be used to enhance the degradation of atrazine in contaminated soils where atrazine is still considered to be recalcitrant. 相似文献
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This study elucidates the effect of fluctuating soil moisture on the co-metabolic degradation of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) in soil. Degradation experiments with 14C-ring-labelled atrazine were carried out at (i) constant (CH) and (ii) fluctuating soil humidity (FH). Temperature was kept constant in all experiments. Experiments under constant soil moisture conditions were conducted at a water potential of −15 kPa and the sets which were run under fluctuating soil moisture conditions were subjected to eight drying-rewetting cycles where they were dried to a water potential of around −200 kPa and rewetted to −15 kPa. Mineralization was monitored continuously over a period of 56 d. Every two weeks the pesticide residues in soil pore water (PW), the methanol-extractable pesticide residues, the non-extractable residues (NER), and the total cell counts were determined. In the soil with FH conditions, mineralization of atrazine as well as the formation of the intermediate product deisopropyl-2-hydroxyatrazine was increased compared to the soil with constant humidity. In general, we found a significant correlation between the formation of this metabolite and atrazine mineralization. The cell counts were not different in the two experimental variants. These results indicate that the microbial activity was not a limiting factor but the mineralization of atrazine was essentially controlled by the bioavailability of the parent compound and the degradation product deisopropyl-2-hydroxyatrazine. 相似文献
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