Evaluation of the Genetic Structure and Functionality of Selected Lead-Resistant Bacteria toward Lead Bioremediation

Abstract

Lead pollution is a major biotic and abiotic stress with significant impact on the environment, public health, and a threat to food security. Hence, the need for an effective and sustainable remediation strategy is strongly required to remove lead pollutants and restore environmental integrity. In this study, four lead-tolerant bacteria, Bacillus infantis strain K66, Halopseudomonas xiamenensis strain B13, Lysinibacillus fusiformis strain KAF67, and Pseudomonas spp. strain A27, were selected for lead bioremediation. The isolates were screened for the presence of lead tolerance gene clusters PbrA, B, C, and T encoding P-type Pb(II) efflux ATPase; predicted integral membrane protein; predicted prolipoprotein signal peptidase; and Pb(II) uptake protein, respectively. All isolates harbored three genes, while KAF67 harbored all. The isolates were utilized for lead treatability study under greenhouse conditions using a block randomized design system for 56 days. Lead bioremediation was monitored biweekly using bacteria counts and lead concentration as monitoring indices. The results revealed a decrease in lead concentration across all pots and a significant difference (P ≤ 0.05) between the lead bacteria–treated pot and control was observed. The rate of removal of lead was the highest in the pot amended with strain K66 (84.64%) and the lowest in the control pot (40.91%). Although the lead removal efficiency varied among treatments, all inoculated pots exhibited significant lead reduction (<80%), highlighting the efficacy of the four lead-resistant bacteria in mitigating lead contamination in soil. Furthermore, this study serves as a demonstration of the efficacy of lead-resistant bacteria with requisite genetic structure toward lead removal from the environment, offering an effective approach to achieving environmental sustainability.