Thiamethoxam degradation by Pseudomonas and Bacillus strains isolated from agricultural soils

Abstract

Twelve bacterial species were evaluated to know the degradation pattern of thiamethoxam in liquid medium. All the bacterial species could actively degrade phorate in a mineral salt medium containing phorate (50 μg ml(-1)) as sole carbon source. As these species have ability to degrade, we used these for the degradation of thiamethoxam--a neonicoitinoids. Screening of 12 active phorate-metabolizing bacterial species resulted in selection of Bacillus aeromonas strain IMBL 4.1 and Pseudomonas putida strain IMBL 5.2 causing 45.28 and 38.23 % thiamethoxam (50 μg ml(-1)) reduction, respectively, in 15 days as potential thiamethoxam degrading species. These two bacterial species grew optimally at 37 °C under shake culture conditions in MSMT medium raised with initial pH of 6.0-6.5 and use of these optimum cultural conditions resulted in improved thiamethoxam degradation by these bacterial species. These species caused maximum thiamethoxam degradation only in the presence of thiamethoxam as sole source of carbon and energy and the same was reduced in the presence of easily metabolize able carbon (C₀ and C₁) and nitrogen ((N₀, N₁ and N₂) sources. This could be attributed to involvement of repressible metabolic pathways, reactions of which are inhibited by the presence of easily available nutrients for growth. Besides above, qualitative analysis of thiamethoxam residues by gas liquid chromatography revealed complete metabolization of thiamethoxam without detectable accumulation of any known thiamethoxam metabolites.

Thiamethoxam removal by Fenton and biological oxidation

“…Although toxic compounds present in natural waters are removed mainly by photodegradation and biodegradation, TMX is poorly degraded by hydrolysis . In fact, TMX biodegradation with pure Rhizobacterium , Pseudomonas and Bacillus strains proved largely inefficient (TMX conversion after 15 days was <45%) …”

“…11 In fact, TMX biodegradation with pure Rhizobacterium, Pseudomonas and Bacillus strains proved largely inefficient (TMX conversion after 15 days was <45%). 12,13 Advanced oxidation processes (AOPs), which provide highly competitive water treatments for removing pesticides refractory to conventional methods, appear to be a good choice for TMX removal. In recent years, a variety of AOPs, but particularly photocatalysis with titanium dioxide (TiO 2 ) and photo-Fenton treatments, have been used successfully to degrade neonicotinoids.…”

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 1: new molecules, metabolism, fate, and transport

“…The same study found no difference in the dissipation of clothianidin from autoclaved soils or nonsterile aerobic soils, demonstrating that microbes are not a factor involved in the degradation of this neonicotinoid. This behavior is in contrast with that of thiamethoxam, which can be degraded by Bacillus aerophilus and Pseudomonas putida in soils (Rana et al 2015). Laboratory cultures (37°C) of these soil microbes were capable of degrading 50 mg/kg thiamethoxam in soil by 38% (P. putida) and 45% (B. aerophilus), with no production of metabolites.…”

Population structure determined by comparative amplicon gene sequencing in biofilm and planktonic bacterial communities from pesticide-contaminated water

“…A strain of Pseudomonas aeruginosa isolated from rice-cultivated soil has the capacity to degrade propiconazole [54]. Other strains of the genus Pseudomonas isolated from agricultural soil degrade thiamethoxam [55].…”