DETECTING TOLERANCE OF Bacillus Subtilis TO THE COMMERCIALLY USED AGRICULTURAL PESTICIDES

Abstract

Bacillus subtilis is an aerobic, spore forming, rod shaped, Gram positive soil bacterium. It is mostly found in soil and vegetation with an optimal growth temperature from 25-35℃. They produce endospores that allow the survival of extreme environmental conditions including heat and desiccation. Pesticides are substances that are meant to control pests. The term pesticide includes herbicides, insecticides, fungicides etc. Most pesticides are intended to serve as plant protection products which in general, protect plants from weeds, fungi, or insects. Because of extended persistence of fungicides, insecticides and herbicides in soil, slow rate of decomposition most of the pesticide residue remain in soil. It is desirable that actual or potential effect upon the soil microflora to be investigated. Hence, main motive of this research was isolation and biochemical characterization of Bacillus subtilis having Plant Growth Promoting Rhizobacterial (PGPR) characteristics from agricultural soil and detecting its tolerance on different pesticides. The bacterial strain was obtained with positive results of Gram staining, endospore staining, catalase degradation, citrate utilization, motility test, VP, starch hydrolysis, gelatin hydrolysis test. The growth promoting activity of bacterial strain was determined by Indole Acetic Acid production test, showed positive test. It was found that Bacillus subtilis was able to tolerate all the pesticide except Mancozeb where it did not show any growth in in-vitro examination. Enumeration of cfu/g soil by periodical interval by serial dilution method (108 cfu/g) showed that all Bacillus isolates were able to grow first 45 day time interval. The number got increased and become higher at the interval of 90 day of inoculation then bacterial number got decreased at 135 day of inoculation. All soil inoculated bacterium with pesticide showed tolerance and gave positive growth in its number. The result of the study showed that the Bacillus spp are very good plant growth promoting agent with great potentiality to grow on pesticide polluted soil.