Screening of lindane degrading bacteria isolated from soil for their plant growth promoting attributes

Abstract

Pesticide degrading bacteria that are isolated from agricultural soils are known to harbor multiple auxiliary characteristics such as production of phytohormone, solubilization of inorganic phosphate, nitrogen fixation, biosurfactant production etc., which are essential for plant growth promotion. In this study, twenty bacterial cultures were isolated from different agricultural fields of Odisha, West Bengal and Manipur (three States of eastern India) by enrichment culture method. These bacteria were isolated based on their ability to grow in media containing mineral salt with lindane at the concentration of 100 mg L−1 as the only carbon utilization source. Along with lindane degradation capacity, the ability of the isolates to promote plant growth was characterized by evaluating their ability for production of ammonia, phytohormones and biosurfactants, solubilization of inorganic phosphates and nitrogen fixation. Preliminary identification of all the isolates was done by morphological as well as biochemical tests. Among the 20 isolates, 8 were found to be Gram−positive and 12 were Gram-negative. The percentage of isolates positive for solubilization of inorganic phosphate, nitrogen fixation, production of indole-3-acetic acid, biosurfactant (in CTAB-methylene blue agar and by hemolysis test in blood agar) and ammonia were 40, 70, 90, 70, 85 and 100% respectively. Finally, three isolates were selected which showed positive results for majority of the tested attributes and identified on the basis of their 16S rRNA gene sequences. It was observed that all the three isolates belonged to the genus Ochrobactrum. Hence it was concluded that along with pesticide utilization these isolates have properties for plant growth promotion and can be potent agents for raising the yield of crops in pesticide-contaminated soils by bioaugmentation.