Pesticide-polluted Soils Research Articles

In situ microbial bioremediation of obsolete pesticides at their disposal sites

Soil pollution by pesticides is a global problem in many countries, including Kyrgyzstan. Currently, 50 storage facilities for obsolete banned pesticides exist, severely threatening the surrounding populations and environment. In this study, in situ bioremediation technology was used to remove pesticide contamination from soil around the storage facilities. Three conditions were tested: application of fertile soil and bioproduct, application of fertile soil and no bioproduct (Control 1), and application of fertile soil and no bioproduct (Control 2). An aerobic bioremediation approach was used: the treatment was applied directly to the contaminated soil. For the bioaugmentation, three selected active degrading bacterial species were used: Stenotrophomonas sp. (Ps-B strain), L. fusiformis (SA-4 strain) and E. cloacae (SB-2 strain). Regular aeration, loosening and watering were performed during the subsequent months to create the conditions required to activate the local microflora and the degrading activity of the bacterial species in the bioproduct. The bioproduct of three active bacteria species has demonstrated a high pesticide decomposition effect. The pesticides were degraded from 85.6 to 99.0 ± 0.05% within six months of initiating the bioremediation process. The efficiency of the degradation process depended on optimum atmospheric conditions, that is, temperature, pH, and moisture content of the soil. Our study recommends using the agrotechnical and biotechnological approach for moderately pesticide-polluted soils and pesticide storage areas.

Activation of persulfate for the degradation of ethyl-parathion in soil: Combined effects of microwave with biochar

Sulfate radical (SO4•−), formed by persulfate (PS) activation during advanced oxidation process (AOPs), can be used for the remediation of organic contaminated soil. However, the role of biochar and microwave (MW) in the activation of PS is not fully understood, especially the corresponding mechanism. Herein, biochar combined with MW was used to activate PS for the remediation of ethyl-parathion (PTH)-polluted soil. The dynamic evolutions of PTH under different conditions, such as biochar content, particle size, reaction temperature, and the degradation mechanisms of PTH were also systematically investigated. Significant enhancement performance on PTH removal was observed after adding biochar, which was 88.78% within 80 min. Meanwhile, activating temperature exhibited remarkable abilities to activate PS for PTH removal. The higher content of adsorption sites in nano-biochar facilitated the removal of PTH. Furthermore, chemical probe tests coupled with quenching experiments confirmed that the decomposition of PS into active species, such as SO4•−, •OH, O2•− and 1O2, contributed to the removal of PTH in biochar combined with MW system, which could oxidize PTH into oxidative products, including paraoxon, 4-ethylphenol, and hydroquinone. The results of this study provide valuable insights into the synergistic effects of biochar and MW in the PS activation, which is helpful for the potential application of biochar materials combined with MW-activated PS in the remediation of pesticide-polluted soils.

Pesticide Soil Pollution: An Overview about Advantages and Disadvantages of Different Remediation Technologies

The use of pesticides presents a looming danger to the living elements of our ecological system, crops, and the well-being of our species. As an outcome, various organic contaminants pollute the soil. Different physical, chemical, and biological remediation techniques have been employed for the decontamination of pesticide-polluted soils. Remediation technology should always be affordable, on-site or in-situ, and capable of restoring the soil's natural functionality. The presence of multiple pesticides can pose challenges in effectively remediating them from the soil. The present work examines the scientific literature on the benefits and drawbacks of various existing and emerging soil remediation techniques. Customized technology choices and designs for specific site conditions enhance the effective cleanup of polluted areas. The present study, which evaluates and contrasts various technological approaches, shall serve as an invaluable tool for determining the optimal soil remediation method for a given contamination dilemma.

In Vitro Biofilm-Mediated Biodegradation of Pesticides and Dye-Contaminated Effluents Using Bacterial Biofilms.

Overuse of pesticides in agricultural soil and dye-polluted effluents severely contaminates the environment and is toxic to animals and humans making their removal from the environment essential. The present study aimed to assess the biodegradation of pesticides (cypermethrin (CYP) and imidacloprid (IMI)), and dyes (malachite green (MG) and Congo red (CR)) using biofilms of bacteria isolated from pesticide-contaminated soil and dye effluents. Biofilms of indigenous bacteria, i.e., Bacillus thuringiensis 2A (OP554568), Enterobacter hormaechei 4A (OP723332), Bacillus sp. 5A (OP586601), and Bacillus cereus 6B (OP586602) individually and in mixed culture were tested against CYP and IMI. Biofilms of indigenous bacteria i.e., Lysinibacillus sphaericus AF1 (OP589134), Bacillus sp. CF3 (OP589135) and Bacillus sp. DF4 (OP589136) individually and in mixed culture were tested for their ability to degrade dyes. The biofilm of a mixed culture of B. thuringiensis + Bacillus sp. (P7) showed 46.2% degradation of CYP compared to the biofilm of a mixed culture of B. thuringiensis + E. hormaechei + Bacillus sp. + B. cereus (P11), which showed significantly high degradation (70.0%) of IMI. Regarding dye biodegradation, a mixed culture biofilm of Bacillus sp. + Bacillus sp. (D6) showed 86.76% degradation of MG, which was significantly high compared to a mixed culture biofilm of L. sphaericus + Bacillus sp. (D4) that degraded only 30.78% of CR. UV-VIS spectroscopy revealed major peaks at 224 nm, 263 nm, 581 nm and 436 nm for CYP, IMI, MG and CR, respectively, which completely disappeared after treatment with bacterial biofilms. Fourier transform infrared (FTIR) analysis showed the appearance of new peaks in degraded metabolites and disappearance of a peak in the control spectrum after biofilm treatment. Thin layer chromatography (TLC) analysis also confirmed the degradation of CYP, IMI, MG and CR into several metabolites compared to the control. The present study demonstrates the biodegradation potential of biofilm-forming bacteria isolated from pesticide-polluted soil and dye effluents against pesticides and dyes. This is the first report demonstrating biofilm-mediated bio-degradation of CYP, IMI, MG and CR utilizing soil and effluent bacterial flora from Multan and Sheikhupura, Punjab, Pakistan.

Biodegradation of Pendimethalin by Three strains of Bacteria Isolated from Pesticide-Polluted Soils

Biodegradation of pendimethalin by three strains of bacteriaviz; Pseudomonas aeruginosa, Bacillus mycoides and Bacillus cereusisolated from pesticides polluted soil was studied in mineral salt medium.Pendimethalin was incubated with each of the three strains of bacteria andsamples were drawn at 0, 3, 7, 15 and 30 days for gas chromatographicanalysis. The loss in the initial concentration (400 ppm) over time wasmonitored and used to compute the half lives following a biphasic model.GC-MS was used to identify the major metabolites as well as to re-confirm the identity of the starting material (pendimethalin). The resultsshowed that the remaining amounts of pendimethalin recovered frommedia inoculated with Pseudomonas aeruginosa for 3, 7, 15 and 30 dayswere; 75.5%, 69.25%, 29.75 % and 19.25% respectively, While theamounts recovered from media inoculated with Bacillus mycoides were;48.75%, 46.25%, 39.25 % and 28.25% following the same order. On theother hand, the respective amounts recovered from media inoculated withBacillus cereus were; 45 %, 32.5 %, 30.5 % and 19.75% at 3, 7, 15 and30 days, respectively. Despite the significant drop in the starting material,no metabolites were detected in Bacillus cultures while only N-(1-ethylpropyl)-3-methyl-2, 6-diaminobenzine was detected in P. aeruginosaculture indicating the capability of these microorganisms of completemineralization of pendimethalin. Pendimethalin biodegradation by thethree types of bacteria followed a biphasic model with faster rate of

Влияние высокоактивных соединений на механические свойства древесины двухлетних сеянцев сосны обыкновенной в лесных питомниках

Scots pine (Pinus sylvestris L.) has the leading environment-forming function. Also, the pine is an economically valuable tree species in the Ural region. The long-term use of the pesticide complex in forest nurseries has led to the pesticide pollution of the arable soil, which causes disruption in the pine seedlings growth, weakening their ability to overcome the difficult period of transportation into the forest environment. The use of biostimulants created from extracts of fir and spruce needles, as well as organic ameliorant (forest litter from pinebirch plantations), is considered as a way to reduce the negative impact of pesticides on pine seedlings. At the same time, biologically active preparations and substrates can lead to shifts in the metabolic processes of young plants, which affect the formation of physical characteristics of the stems. The research aims at assessing how wood density changes under the influence of highly active substances of different nature in two-year-old Scots pine seedlings grown in forest nurseries of the Middle Urals. The study objects were two-years-old pine seedlings dug out in autumn from sylvicultural fields and experimental sites in different forest nurseries. Morphometric parameters of seedlings were determined in the laboratory conditions. The basic wood density of stems in the 1st and 2nd years of growth was determined by the method of maximum humidity. It was found that the metabolic activity of pesticides and biostimulants leads to changes in the formation of physical properties of stems at the initial stages of pine growth: when growing seedlings in pesticide-polluted soil, the height of seedlings is lower, and the basic density of stem wood is higher, compared to control group. Forest litter from mixed plantations (birch-pine), when introduced to the forest nursery soil, produces seedlings of greater height and has no significant effect on the formation of physical and mechanical properties of wood. The seed treatment by biostimulants leads to a rapid increase in the stems size, but the wood density decreases, relative to the control option. Corrective measures and the development of balanced agronomic machinery for production of pine with the required physical qualities of wood are needed in the future. The study of the qualitative characteristics formation features of trees, when using intensive technologies in nurseries, is necessary for the development of target models for the subsequent use of such seedlings in forest management.

Biodegradation of chlorpyrifos by bacterial strains isolated from Lebanese soil and its association with plant growth improvement

Chlorpyrifos poses a danger to the environment as a result of its toxicity and endurance in soil and water. Bioremediation of pesticide-polluted soils is one of the most promising approaches for removing contaminants from the environment. This study aimed to isolate and identify chlorpyrifos-degrading bacterial strains and test their biodegradation capabilities and their roles in plant growth. The 16S rDNA gene sequencing identified the two efficient chlorpyrifos-degrading bacterial strains as Stenotrophomonas maltophilia (RS1) and Acinetobacter calcoaceticus (RS3), which significantly (p < 0.01) degraded 71.3% and 73.5% of chlorpyrifos in the liquid medium, respectively, compared to 80% degradation (p < 0.01) when cultured as a consortium within 48 h. The bioremediation of artificially chlorpyrifos-contaminated soils varied between 84.4% and 90.11% (p < 0.01), depending on the used bacterium and soil sterilization status. Furthermore, the enzymes embroiled in the degradation mechanism were sprinkled all over the cells but with different portions. Experiments on plant growth revealed that chlorpyrifos hurt lettuce growth. The presence of RS1 and RS3, on the other hand, demonstrated considerable lettuce growth-enhancing traits in terms of germination percentages, shoot and root lengths and weights. Our isolates could be promising candidates in the bioremediation of chlorpyrifos-contaminated sites in conjunction with their contribution as biofertilizers.

A review on effective soil health bio-indicators for ecosystem restoration and sustainability.

Preventing degradation, facilitating restoration, and maintaining soil health is fundamental for achieving ecosystem stability and resilience. A healthy soil ecosystem is supported by favorable components in the soil that promote biological productivity and provide ecosystem services. Bio-indicators of soil health are measurable properties that define the biotic components in soil and could potentially be used as a metric in determining soil functionality over a wide range of ecological conditions. However, it has been a challenge to determine effective bio-indicators of soil health due to its temporal and spatial resolutions at ecosystem levels. The objective of this review is to compile a set of effective bio-indicators for developing a better understanding of ecosystem restoration capabilities. It addresses a set of potential bio-indicators including microbial biomass, respiration, enzymatic activity, molecular gene markers, microbial metabolic substances, and microbial community analysis that have been responsive to a wide range of ecosystem functions in agricultural soils, mine deposited soil, heavy metal contaminated soil, desert soil, radioactive polluted soil, pesticide polluted soil, and wetland soils. The importance of ecosystem restoration in the United Nations Sustainable Development Goals was also discussed. This review identifies key management strategies that can help in ecosystem restoration and maintain ecosystem stability.

The efficient persistence and migration of Cupriavidus gilardii T1 contribute to the removal of MCPA in laboratory and field soils

The application of exogenous biodegradation strains in pesticide-polluted soils encounters the challenges of migration and persistence of inoculants. In this study, the degradation characteristics, vertical migration capacity, and microbial ecological risk assessment of an enhanced green fluorescent protein (EGFP)-tagged 2-Methyl-4-chlorophenoxyacetic acid (MCPA)-degrading strain Cupriavidus gilardii T1 (EGFP) were investigated in the laboratory and field soils. The optimum remediation conditions for T1 (EGFP) was characterized in soils. Meanwhile, leaching experiments showed that T1 (EGFP) migrated vertically downwards in soil and contribute to the degradation of MCPA at different depths. After inoculation with T1 (EGFP), a high expression levels of EGFP gene was observed at 28 d in the laboratory soil and at 45 d in the field soil. The degradation rates of MCPA were ≥ 60% in the laboratory soil and ≥ 48% in the field soil, indicating that T1 (EGFP) can efficiently and continuously remove MCPA in both laboratory and field conditions. In addition, the inoculation of T1 (EGFP) not only showed no significant impact on the soil microbial community structure but also can alleviate the negative effects induced by MCPA to some extent. Overall, our findings suggested that T1 (EGFP) strain is an ecologically safe resource for the in situ bioremediation of MCPA-contaminated soils.

Conceptual approaches to rehabilitation of pesticide-polluted soils of Ukraine

The Concept of Rehabilitation of Contaminated Soils has been developed, which substantiates the ways to restore areas contaminated with persistent organic pesticides. The practical implementation of the Concept will contribute to the transfer of existing land use systems to the principles of sustainable agricultural development, as well as the preservation, reproduction and expansion of biodiversity, as well as improving the environmental safety of agro-ecosystems for sustainable development of the Agrosphere. The Concept combines ways of practical implementation of environmentally friendly methods of cleaning pesticide-contaminated areas and further use of rehabilitated land in the process of agricultural activity in Ukraine. The problem of pesticide pollution of agroecosystems is proposed to be solved by using scientifically sound ecologically safe methods of soil remediation with multicomponent pesticide pollution developed at the Institute of Agroecology and Environmental Management of NAAS, in particular using bioremediation methods. The following are proposed for use: methods of agroecological monitoring of areas contaminated with persistent organic pollutants, methods of phytotesting and phytoremediation of soils contaminated with resistant pesticides. For phytoremediation of contaminated soils, it is proposed to use annual cultivated (barley, wheat, beans, soybeans, zucchini, pumpkin) and wild (dandelion, bitter wormwood, common wormwood, wheatgrass) species of plant-mediators, which are suitable for phytostabilation and in the conditions of multicomponent soil pollution. The main stages of the Concept implementation are: complex agroecological monitoring of soils contaminated with residues of persistent organic pollutants (POPs); comprehensive ecotoxicological assessment of soil condition; determining the degree of chemical degradation of soils; adaptation of remediation technologies to the specifics of the area in need of cleaning; introduction of ecologically safe remediation methods into practical use; realization of prospects of further use of rehabilitated soils in various branches of agriculture; taking into account the ecological and economic efficiency of the use of remediation methods. Possibility and ways of using restored areas in the process of agricultural activity, taking into account the main stages of implementation of the Concept are set out in the developed in the Institute of Agroecology and Environmental Management of NAAS «Scientific and methodological recommendations for restoration of soil contaminated with organochlorine pesticides depending on their toxicity» and «Scientific and methodological recommendations for the use of restored areas in the process of agricultural activity».

Photodegradation of endosulfan and pendimethalin in sunlight

The potential of sunlight photolysis in remediation of pesticide-polluted soils in Sudan is reported. The common pollutants endosulfan (alpha- and beta- isomers) and pendimethalin were exposed to sunlight over glass and soil surfaces and the periodically drawn samples were analyzed by GC-ECD and GC-MS. Photo-degradation followed biphasic model. The half-lives of direct photolysis of the two pesticides over glass and soil surfaces ranged between 1.840-6.720 d and 2.711 to 9.760 d respectively. The respective values for indirect photolysis of the two pesticides with β-carotene over glass surface were 0.846-1.605 d and for benzophenone 1.050-1.626 d. Values for soil β-carotene sensitized photolysis of the two pesticides were 2.260-3.158 d while the corresponding values for benzophenone sensitized photolysis on soil were 1.193-2.880 d. Meteorological factors did not show significant impact on photolysis rates. Despite the significant decrease in starting material in direct no photoproducts were detected. However, many photoproducts were detected on the indirect sets. Photo-degradation efficiency can be arranged in the order benzophenone > β-carotene > direct exposure.

Assessment of the Microbial Biomass Carbon (MB-C), Nitrogen (MB-N) and Phosphorus (MB-P) in Soil Spiked with Pesticides (Carbofuran and Paraquat)

This study aimed at determining the impact of Carbofuran and Paraquat use on soil microbial biomass and microbial population as soil health index. Pot experiment, set-up as a randomized block design with replicates was done, with both pesticides applied at recommended rates for eight weeks. Twenty-four (24) soil samples were taken from the pesticides polluted soil as well as the unpolluted soil. These samples were used to assess the effect of pesticides on microbial biomass carbon (MB-C), nitrogen (MB-N) and phosphorus (MB-P). Also, microbial population (determined by aerobic spread plate count) of the pesticide-polluted soils was used as health index. The assessments were done weekly. The microbial biomass values increased from 273.48 µg/g to 293.15 µg/g (MB-C), 17.275 µg/g to 18.52 µg/g (MB-N) and 10.605 µg/g to 11.37 µg/g (MB-P) in carbofuran treated soil while increases from 277.26 µg/g to 288.365 µg/g (MB-C), 17.515 µg/g to 18.22 µg/g (MB-N) and 10.745 µg/g to 11.18 µg/g (MB-P) were observed in paraquat treated soil. The microbial counts in treated soils were within the ranges of 1.95 x 106 cfu/g to 1.03 x 107 cfu/g, 8.83 x 104 to 1.90 x 105 cfu/g, 1.08x 104 to 2.43 x 104, 1.15 x105 to 2.17 x 105 cfu/g, 1.38 x 105 to 2.22 x 105 cfu/g for total heterotrophic bacterial, fungal, actinomycetes, phosphate solubilizers, nitrifiers counts, respectively.&#x0D; The pesticides had no negative effects on the MB-C, MB-N, MB-P and soil microorganisms at recommended field rates, hence their use must be strictly based on these rates. These findings indicate that the relationship between soil nutrients and microbial biomass is significant in facilitating the use of microbial biomass as an important soil quality indicator.

Paraquat Degradation From Contaminated Environments: Current Achievements and Perspectives.

Paraquat herbicide has served over five decades to control annual and perennial weeds. Despite agricultural benefits, its toxicity to terrestrial and aquatic environments raises serious concerns. Paraquat cannot rapidly degrade in the environment and is adsorbed in clay lattices that require urgent environmental remediation. Advanced oxidation processes (AOPs) and bioaugmentation techniques have been developed for this purpose. Among various techniques, bioremediation is a cost-effective and eco-friendly approach for pesticide-polluted soils. Though several paraquat-degrading microorganisms have been isolated and characterized, studies about degradation pathways, related functional enzymes and genes are indispensable. This review encircles paraquat removal from contaminated environments through adsorption, photocatalyst degradation, AOPs and microbial degradation. To provide in-depth knowledge, the potential role of paraquat degrading microorganisms in contaminated environments is described as well.

Photodegradation of chlorpyrifos, malathion, and dimethoate by sunlight in the Sudan

The potential of sunlight photolysis in remediation of pesticide-polluted soils in Sudan was studied. Chlorpyrifos, malathion and dimethoate, common pollutants, were exposed to sunlight over glass and soil surfaces with periodic samples drawn for GC and GC-MS analysis. Photo-degradation followed a biphasic model. Alpha half-lives of direct photolysis over glass surface range between 1.99 and 9.36 days while the range in soil surfaces is 1.88–10.77 days. Respective values for indirect photolysis with β-carotene are 0.96–2.40 days whereas for benzophenone are 0.38–2.37 days (not including malathion as starting material was completely lost after 3 days). Values for soil β-carotene sensitized photolysis are 0.85–4.02 days while respective values for soil benzophenone sensitized photolysis are 0.88–3.74 days. Metrological factors did not have a significant impact on photolysis rates. No photoproducts detected in direct photolysis. However, many photoproducts were detected on the indirect sets. Photo-degradation efficiency can be ordered as; benzophenone > β-carotene > direct exposure.

English

The objective of this study was to evaluate the capability of the bacteria Bacillus safensis strain FO-36bT isolated from pesticide-polluted soil in degrading fenthion and temphos in mineral salt media (MSM). Fenthion and temphos were incubated with the isolated bacteria. Samples were drawn at 0, 3, 7, 14, and 30 days to analyze residual fenthion and temphos content with gas chromatography (GC) and high-performance liquid chromatography (HPLC), respectively. The loss of the initial pesticide concentration (400 mg/L) over time was determined and used to compute the half-lives using a biphasic model. Gas chromatography-mass spectrometry (GC-MS) was used to identify the major metabolites as well as to re-confirm the identity of starting material (fenthion). The results showed that the bacterium was still viable at the end of each incubation period. The biodegradation of fenthion and temphos followed a biphasic model. The half-lives of fenthion in the first and in the second phase were 0.29 and 3.69 days, respectively, whereas the corresponding values for temphos were 0.11 and 1.15 days. Only one metabolite &quot;iso-fenthion&quot; (O, S-dimethyl O-[3-methyl-4-(methylthio)phenyl] phosphorothioate) was detected in fenthion culture, while no metabolites were detected in temphos culture. Based on the half-lives, this bacterium was able to degrade temphos at a faster rate than fenthion.&nbsp; &nbsp; &nbsp; Key words: Biodegradation, fenthion, temphos, bacteria, pesticides-contaminated soil, Sudan.

Biodegradation of Chlorpyrifos, Malathion, and Dimethoate by Three Strains of Bacteria Isolated from Pesticide-Polluted Soils in Sudan

This study was done to identify pesticide-biodegrading microorganisms and to characterize degradation rates. Bacillus safensis strain FO-36bT, Bacillus subtilis subsp. inaquosorum strain KCTC13429T, and Bacillus cereus strain ATCC14579T were isolated from pesticide-polluted soil in Sudan, separately incubated with each pesticide with periodic samples drawn for GC and GC-MS. Pesticide biodegradation followed a biphasic model. α and β half-lives (days) of chlorpyrifos, malathion, and dimethoate in B.safensis culture were 2.13, 4.76; 2.59, 5.66; and 9.5, 11.0, respectively. Values in B.subtilis and B.cereus cultures were 4.09, 9.45 and 4.33, 9.99 for chlorpyrifos; 2.99, 5.36 and 2.43, 4.71 for malathion; and 9.53, 15.11 and 4.16, 9.27 for dimethoate. No metabolite was detected in B.subtilis cultures, whereas a few were detected from B.safensis and B.cereus cultures. Bacterial efficiency can be ordered as B.safensis > B.subtilis > B.cereus for chlorpyrifos and B.cereus > B.subtilis > B.safensis for malathion and dimethoate.

Performance of trichlorfon degradation by a novel Bacillus tequilensis strain PA F-3 and its proposed biodegradation pathway.

The novel trichlorfon (TCF)-degrading bacterium PA F-3, identified as Bacillus tequilensis, was isolated from pesticide-polluted soils by using an effective screening and domesticating procedure. The TCF biodegradation pathways of PA F-3 were also systematically elucidated. As revealed by high-performance liquid chromatography, the TCF residues in the mineral salt medium demonstrated that PA F-3 can utilize TCF as its sole carbon source and reach the highest degradation of 71.1% at an initial TCF concentration of 200mg/L within 5days. The TCF degradation conditions were optimized using response surface methodology as follows: temperature, 28°C; inoculum amount, 4%; and initial TCF concentration, 125mg/L. Biodegradation treatments supplemented with exogenous carbon sources and yeast extract markedly increased the microbial dry weights and TCF-degrading performance of PA F-3, respectively. Meanwhile, five metabolic products of TCF were identified through gas chromatography/mass spectrometry, and a biodegradation pathway was proposed. Results indicated that deoxidation and dehydration (including the cleavage of the P-C phosphonate bond and the C-O bond) were the preferred metabolic reactions of TCF in this TCF-degrading bacterium.

Biodegradation of the Organophosphate Trichlorfon and Its Major Degradation Products by a Novel Aspergillus sydowii PAF-2.

Trichlorfon (TCF) is an important organophosphate pesticide in agriculture. However, limited information is known about the biodegradation behaviors and kinetics of this pesticide. In this study, a newly isolated fungus (PA F-2) from pesticide-polluted soils was identified as Aspergillus sydowii on the basis of the sequencing of internal transcribed spacer rDNA. This fungus degraded TCF as sole carbon, sole phosphorus, and sole carbon-phosphorus sources in a mineral salt medium (MSM). Optimal TCF degradation conditions were determined through response surface methodology, and results also revealed that 75.31% of 100 mg/L TCF was metabolized within 7 days. The degradation of TCF was accelerated, and the mycelial dry weight of PA F-2 was remarkably increased in MSM supplemented with exogenous sucrose and yeast extract. Five TCF metabolic products were identified through gas chromatography-mass spectrometry. TCF could be initially hydrolyzed to dichlorvos and then be degraded through the cleavage of the P-C bond to produce dimethyl hydrogen phosphate and chloral hydrate. These two compounds were subsequently deoxidized to produce dimethyl phosphite and trichloroethanal. These results demonstrate the biodegradation pathways of TCF and promote the potential use of PA F-2 to bioremediate TCF-contaminated environments.

Stimulation of soil microorganisms in pesticide-contaminated soil using organic materials

Agrochemicals such as pesticides have contributed to significant increases in crop yields; however, they can also be linked to adverse effects on human health and soil microorganisms. For efficient bioremediation of pesticides accumulated in agricultural fields, stimulation of microorganisms is necessary. In this study, we investigated the relationships between bacterial biomass and total carbon (TC) and total nitrogen (TN) in 427 agricultural soils. The soil bacterial biomass was generally positively correlated with TC and TN contents in the soil, but some soils had a low bacterial biomass despite containing high amounts of TC and TN. Soils of two fields (fields A and B) with low bacterial biomass but high TC and TN contents were investigated. Long-term pesticide use (dichloropropane-dichloropropene and fosthiazate in field A and chloropicrin in field B) appeared to have contributed to the low bacterial biomass observed in these soils. Soil from field A was treated with different organic materials and incubated for 1 month under laboratory conditions. The bacterial biomass in field A soil was enhanced in treatments containing organic materials rich in TN. Application of organic materials stimulated the growth of microorganisms with the potential to bioremediate pesticide-polluted soils.

Genome Sequence of Organophosphorus Pesticide-Degrading Bacterium Pseudomonas stutzeri Strain YC-YH1.

Pseudomonas stutzeri strain YC-YH1, isolated from pesticide-polluted soil, efficiently degrades organophosphorus pesticides (OPPs) such as chlorpyrifos, parathion-methyl, triazophos, and parathion. Here, we report the genome sequence (4.83 Mb) of P. stutzeri YC-YH1 to facilitate further investigation of the OPP-degrading mechanism.