Characterization of a bacterium tolerant of spill levels of the herbicide alachlor
1993
Khan, Y.H. | Harris, R.F. (Wisconsin Univ., Madison (USA). Dept. of Soil Science)
Soils treated with five levels of alachlor (4, 40, 400, 4000, and 40000 lbs/ac), were plated on to a range of media i.c. concentrated and nutritionally rich nutrient broth medium (NB) relatively dilute but nutritionally rich diluted nutrient broth medium (DNB) and relatively dilute and nutritionally poor diluted glucose yeast extract medium (DGY). [all amended with four levels of alachlor (200, 2000, 4000, and 20000 ppm)]. Representative colony-morphology-distinct microorganisms were isolated from their respective NB, DNB and DGY media. Isolates were run through a characterization scheme developed on the basis of gross difference in the characterization of predominant aerobic heterotrophic soil bacteria. The characterization was narrowed down to a limited number of biochemical tests keeping in view these generals and gross differences between aerobic heterotrophic soil bacteria. Gram-negative short rods Pseudomonas/ Alcaliqenese group appeared to be predominant in all alachlor amended plates and was found to tolerate alachlor at the level of 4000 ppm in the relatively diluted and nutritionally poor medium. The Acinetobacter also made significant appearance but failed to grow beyond 200 ppm concentrations of alachlor in all the supplemented systems. Plates containing 20,000 ppm alachlor lacked any microbial growth. It appeared that isolates made from soils amended with higher concentrations of the herbicide. The present data indicates that microorganisms exposed to higher concentrations of alachlor in the soil systems might have developed the herbicide tolerance.
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