Plants are a source of wide range of bioactive molecules. Alstonia scholaris, a tree species of Apocynaceae family is being reported as a well known herbal remedy of various diseases. In the present investigation, n-hexane fraction of crude methanolic extract of Alstonia scholaris Linn. R.Br. stem bark was evaluated for antibacterial activity using four human pathogenic multi-drug resistance bacterial strains Enterobacteriaceae bacterium IK1_01, Shigella dysentery, Enterobacter cloacae and Serratia marcescens. Antibiotic susceptibility tests were also performed to evaluate the multi-drug resistance patterns of these strains. All the strains showed multi-drug resistance against several commercially available antibiotics. The n-hexane fraction showed significant inhibitory activities against all the strains by agar-diffusion assay. The n-hexane fraction of crude methanolic extract of stem of A. scholaris showed MICs of 5.5 mg/ml, 5 mg/ml, <5.5 mg/ml and 8 mg/ml, and induced a maximum of 85.7%, 95.6%, 89.3% and 94.4% growth inhibition against E. bacterium IK1_01, S. dysentery, E. cloacae and S. marcescens, respectively.
The present study reports on the isolation and characterization of a Pseudomonas aeruginosa strain PTz-5 from crude oil from oil field sampled in Assam, India. It was capable to utilize hexadecane, benzene or toluene as a sole source of carbon aerobically. Strain PTz-5 was able to produce extracellular lipase that catalyzed triglycerides to free fatty acid and glycerol. The lipase activity was stable in the temperature range of 40 to 60 degrees C. Strain PTz-5 avidly adhered to the surface of hydrocarbon droplets during their growth in liquid culture medium. These properties could play an essential role in hydrocarbon degradation. The results presented here highlight the metabolic versatility and hydrocarbon biodegradative capability of strain PTz-5, signifying its great potential for the bioremediation of various hydrocarbon-contaminated environments.
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