Analyses of the Heavy Metal Resistance Pattern and Biosorption Potential of an Indigenous Bacillus tropicus Strain Isolated from Arable Soil

Abstract

Heavy metal contamination has a significant impact on the environment and is a matter of global concern. Microorganisms, particularly bacteria, have evolved specific resistance mechanisms to metabolize and convert heavy metals into less toxic forms. The primary goal of this study was to explore naturally occurring indigenous bacteria from arable land and investigate their role in the eco-friendly recovery of heavy metal pollutants from arable land. In this study, 18 heavy metal resistant bacterial isolates were obtained from the arable soil of Dakshin Dinajpur region of West Bengal, India. A potent bacterial isolate (Bacillus tropicus MCCC 1A01406), was obtained demonstrating resistance against multiple heavy metals like Pb, Cr, Cd, Cu, Ni, Fe, Zn, and Co. The effect of heavy metals on the growth kinetics, heavy metal uptake, and antibiotic susceptibility of the isolate was studied in detail. The isolate was found to be efficient in Pb uptake and demonstrated relatively higher biological Pb removal efficiency and capacity in comparison to other Bacillus strains reported in the literature. The Pb biosorption capability of the isolate was interpreted using Langmuir and Freundlich’s adsorption isotherms. The experimental data fitted well with the Langmuir model, suggesting monolayer type adsorption. The isolate also demonstrated resistance against antibiotics like doxycycline, nalidixic acid, kanamycin, imipenem, metronidazole, ceftriaxone, and amoxicillin.