Bioremediation of organophosphorus pesticide phorate in soil by microbial consortia.

Microbial consortia isolated from aged phorate contaminated soil were used to degrade phorate. The consortia of three microorganisms (Brevibacterium frigoritolerans, Bacillus aerophilus and Pseudomonas fulva) could degrade phorate, and the highest phorate removal (between 97.65 and 98.31%) was found in soils inoculated with mixed cultures of all the three bacterial species. However, the mixed activity of any of two of these bacteria was lower than mixed consortia of all the three bacterial species. The highest degradation by individual mixed consortia of (B. frigoritolerans+B.aerophilus, B. aerophilus+P. fulva and B. frigoritolerans+P. fulva) appeared in soil between (92.28-94.09%, 95.45-97.15% and 94.08-97.42%, respectively). Therefore, inoculation of highly potential microbial consortia isolated from in situ contaminated soil could result in most effective bioremediation consortia for significantly relieving soils from phorate residues. This much high phorate remediation from phorate contaminated soils have never been reported earlier by mixed culture of native soil bacterial isolates.

Novel surface antigen based impedimetric immunosensor for detection of Salmonella typhimurium in water and juice samples.

A specific surface antigen, OmpD has been reported first time as a surface biomarker in the development of selective and sensitive immunosensor for detecting Salmonella typhimurium species. The OmpD surface antigen extraction was done from Salmonella typhimurium serovars, under the optimized growth conditions for its expression. Anti-OmpD antibodies were generated and used as detector probe in immunoassay format on graphene-graphene oxide (G-GO) modified screen printed carbon electrodes. The water samples were spiked with standard Salmonella typhimurium cells, and detection was done by measuring the change in impedimetric response of developed immunosensor to know the concentration of serovar Salmonella typhimurium. The developed immunosensor was able to specifically detect S. typhimurium in spiked water and juice samples with a sensitivity upto 10(1)CFUmL(-1), with high selectivity and very low cross-reactivity with other strains. This is the first report on the detection of Salmonella typhimurum species using a specific biomarker, OmpD. The developed technique could be very useful for the detection of nontyphoidal Salmonellosis and is also important from an epidemiological point of view.

Isolation and evaluation of potent Pseudomonas species for bioremediation of phorate in amended soil.

Use of phorate as a broad spectrum pesticide in agricultural crops is finding disfavor due to persistence of both the principal compound as well as its toxic residues in soil. Three phorate utilizing bacterial species (Pseudomonas sp. strain Imbl 4.3, Pseudomonas sp. strain Imbl 5.1, Pseudomonas sp. strain Imbl 5.2) were isolated from field soils. Comparative phorate degradation analysis of these species in liquid cultures identified Pseudomonas sp. strain Imbl 5.1 to cause complete metabolization of phorate during seven days as compared to the other two species in 13 days. In soils amended with phorate at different levels (100, 200, 300 mg kg(-1) soil), Pseudomonas sp. strain Imbl 5.1 resulted in active metabolization of phorate by between 94.66% and 95.62% establishing the same to be a potent bacterium for significantly relieving soil from phorate residues. Metabolization of phorate to these phorate residues did not follow the first order kinetics. This study proves that Pseudomonas sp. strain Imbl 5.1 has huge potential for active bioremediation of phorate both in liquid cultures and agricultural soils.

Brevibacterium frigoritolerans as a Novel Organism for the Bioremediation of Phorate.

Phorate, an organophosphorus insecticide, has been found effective for the control of various insect pests. However, it is an extremely hazardous insecticide and causes a potential threat to ecosystem. Bioremediation is a promising approach to degrade the pesticide from the soil. The screening of soil from sugarcane fields resulted in identification of Brevibacterium frigoritolerans, a microorganism with potential for phorate bioremediation was determined. B. frigoritolerans strain Imbl 2.1 resulted in the active metabolization of phorate by between 89.81% and 92.32% from soils amended with phorate at different levels (100, 200, 300 mg kg(-1) soil). But in case of control soil, 33.76%-40.92% degradation were observed. Among metabolites, sulfone was found as the main metabolite followed by sulfoxide. Total phorate residues were not found to follow the first order kinetics. This demonstrated that B. frigoritolerans has potential for bioremediation of phorate both in liquid cultures and agricultural soils.

Bioremediation of fipronil by a Bacillus firmus isolate from soil.

Persistence of fipronil, a new molecule in extensive use against various insect pests is causing serious problems to the environment. Bacillus firmus was isolated by selective enrichment from soil samples collected from sugar fields with known history of pesticide usage and evaluated for metabolization of fipronil in clay loam soil. Soil samples in 50 g aliquotes were fortified with fipronil @ 0.50-1.50 mg kg(-1) and inoculated with B. firmus cells (45×10(7) CFU mL(-1)) and incubated at 25 °C. Each sample in triplicates was drawn periodically up to 56 d and residual fipronil contents analyzed by gas liquid chromatograph. Fipronil residues were not detected after 35 d at lower doses of fipronil (@ 0.50, 0.75 and 1.00 mg kg(-1)). However, at higher doses (@ 1.25 and 1.50 mg kg(-1)) than this total metabolization of fipronil could be observed after 35 and 42 d, respectively. Thus whereas, B. firmus proved its potential in efficient metabolization of fipronil, the period required for the same was dose dependent. Amongst various metabolites of fipronil degradation, fipronil sulfide was found to be the main metabolite followed by fipronil sulfone and fipronil amide. Though, desulfinyl metabolite earlier reported as one of the main metabolite of fipronil degradation, the existence of the same was not detected in any of the treatment.

Isolation and characterization of novel phorate-degrading bacterial species from agricultural soil.

Based upon 16S rDNA sequence homology, 15 phorate-degrading bacteria isolated from sugarcane field soils by selective enrichment were identified to be different species of Bacillus, Pseudomonas, Brevibacterium, and Staphylococcus. Relative phorate degradation in a mineral salt medium containing phorate (50 µg ml(-1)) as sole carbon source established that all the bacterial species could actively degrade more than 97 % phorate during 21 days. Three of these species viz. Bacillus aerophilus strain IMBL 4.1, Brevibacterium frigoritolerans strain IMBL 2.1, and Pseudomonas fulva strain IMBL 5.1 were found to be most active phorate metabolizers, degrading more than 96 % phorate during 2 days and 100 % phorate during 13 days. Qualitative analysis of phorate residues by gas liquid chromatography revealed complete metabolization of phorate without detectable accumulation of any known phorate metabolites. Phorate degradation by these bacterial species did not follow the first-order kinetics except the P. fulva strain IMBL 5.1 with half-life period (t1/2) ranging between 0.40 and 5.47 days.

Microbial degradation of fipronil by Bacillus thuringiensis.

Fipronil, a phenyl pyrazole insecticide has been found to be effective for the control of various insect pests. Due to its higher persistence in soil bioremediation is a promising approach to degrade the pesticide from soil. Isolation and identification of soil microbes was conducted for bioremediation of fipronil contaminated soils. Soil samples collected from different sugarcane growing fields in Gurdaspur district with extensive use of pesticide history served as a source of pesticide degrading microbes. The microbe cultures were grown in Luria broth and maintained at 28°C. After that Dorn's broth enrichment culture supplemented with fipronil was used and Bacillus thuringiensis were isolated. Clay loam soil samples were fortified with fipronil @ 0.50, 0.75, 1.00, 1.25 and 1.50mgkg(-1) along with 45×10(7) microbe cells. Each treatment was replicated thrice and from each fortified (insecticide+microbes) sample, 50g soil sample was taken at 7, 14, 28, 35, 42, 49 and 56 days after initiation of this experiment. Residues were not detected after 28, 35, 35, 35 and 42 days in soil samples after fortification with fipronil @ 0.50, 0.75, 1.00, 1.25 and 1.50mgkg(-1). Among metabolites, sulfide was found to be the main metabolite followed by sulfone and amide. Desulfinyl metabolite was not produced in any of the sample. Total fipronil residues were not found to follow the first order kinetics.