ABSTRACT
BACKGROUND: The extensive and intensive uses of organophosphorus insecticide-quinalphos in agriculture, pose a health hazard to animals, humans, and environment because of its persistence in the soil and crops. However, there is no much information available on the biodegradation of quinalphos by the soil micro-organisms, which play a significant role in detoxifying pesticides in the environment; so research is initiated in biodegradation of quinalphos. RESULTS: A soil bacterium strain, capable of utilizing quinalphos as its sole source of carbon and energy, was isolated from soil via the enrichment method on minimal salts medium (MSM). On the basis of morphological, biochemical and 16S rRNA gene sequence analysis, the bacterium was identified as to be Bacillus thuringiensis. Bacillus thuringiensis grew on quinalphos with a generation time of 28.38 min or 0.473 h in logarithmic phase. Maximum degradation of quinalphos was observed with an inoculum of 1.0 OD, an optimum pH (6.5-7.5), and an optimum temperature of 35-37 °C. Among the additional carbon and nitrogen sources, the carbon source-sodium acetate and nitrogen source-a yeast extract marginally improved the rate of degradation of quinalphos. CONCLUSIONS: Display of degradation of quinalphos by B. thuringiensis in liquid culture in the present study indicates the potential of the culture for decontamination of quinalphos in polluted environment sites.
ABSTRACT
Studies were undertaken to examine the mechanism of mediation of silver nanoparticles in inhibiting biofilm formation by Pseudomonas aeruginosa through LuxI/LuxR system of signal transduction. This study includes the basic signaling transduction mechanism LasR, QscR, RhlR, and Vfr signaling model systems. The arbitrary homology models built with the I-TASSER server were evaluated and validated with the Qmean web server. Based on the Z-score and the relative square mean distance (RMSD) values, the structures were validated. The interaction results of the nanoparticle with the rigid docking proved the requirement of minimal energy for the inhibition of the protein active site by the silver nanoparticle. This principle docking experiment suggests that the biofilm formation in Gram-negative bacteria can be inhibited by the silver nanoparticles at the signal transduction level. Graphical abstract Systematic outline of present study; Stage one provides the data sampling and generation of pdb systems to conform the structure of bacterial signal sytems like LasR/LasI; RhlR/RhrI; QscR/QscI; VfrR/VfrI. Stage two involves docking of silver nanoparticles with Bacterial signal protein strucutres which are listed in Stage one. The Final Stage involves in understanding the development of appropriate mechanism behind the biofilm inhibition by silver nanoparticles.
