Mechanism of lead adsorption by a Bacillus cereus strain with indole-3-acetic acid secretion and inorganic phosphorus dissolution functions

Abstract

Background Heavy metal pollution has become a major source of environmental pollution because of increasing industrialization. Microbial remediation is a promising approach to remediate lead-contaminated environments owing to its cost-effective, environment-friendly, ecologically sustainable, and highly efficient properties. In this study, the growth-promoting functions and lead-adsorption ability of Bacillus cereus SEM-15 were examined, and the functional mechanism of the strain was preliminarily identified using scanning electron microscopy, energy spectrum, infrared spectrum, and genome analyses, providing theoretical support for utilization of B. cereus SEM-15 in heavy metals remediation. Results B. cereus SEM-15 showed strong ability to dissolve inorganic phosphorus and secrete indole-3-acetic acid. The lead adsorption efficiency of the strain at lead ion concentration of 150 mg/L was more than 93%. Single factor analysis revealed the optimal conditions for heavy metal adsorption by B. cereus SEM-15 (adsorption time, initial lead ion concentration, pH, and inoculum amount were 10 min, 50–150 mg/L, 6–7, and 5 g/L, respectively) in nutrient-free environment, with the lead adsorption rate reaching 96.58%. Scanning electron microscopy of B. cereus SEM-15 cells before and after lead adsorption showed adherence of a large number of granular precipitates to the cell surface after lead adsorption. X-Ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results indicated the characteristic peaks of Pb–O, Pb–O-R (R = functional group), and Pb–S bonds after lead adsorption, and a shift in the characteristic peaks of bonds and groups related to C, N, and O. Genome annotation results showed the presence of genes related to heavy metals tolerance and plant growth promotion in B. cereus SEM-15, providing a molecular basis for the strain’s heavy metals tolerance and plant growth promotion functions. Conclusions This study analyzed the lead adsorption characteristics of B. cereus SEM-15 and the associated influencing factors, and discussed the adsorption mechanism and related functional genes, providing a basis for clarifying the underlying molecular mechanism and offering a reference for further research on plant-microorganisms combined remediation of heavy metals polluted environments.

Lead (Pb)-Resistant Bacteria Improve <i>Brassica chinensis</i> Biomass and Reduce Pb Concentration in Pb-Contaminated Soil

“…The treatment reduced Pb residue by up to 88% compared to the control; the remaining Pb residue was only 10 mg/kg (Figure 6). The low Pb residue in the soil on TSB treatment was due to B. wiedmannii adsorb Pb, as a previous study reported that B. cereus, which is closely related to B. wiedmannii can absorb Pb up to 96.58% through several mechanisms such as indole-3-acetic acid (IAA) secretion and inorganic phosphorus (P) dissolution (Miller et al 2016;Li et al 2023). Besides Pb adsorption ability, the bacterium is a biocontrol agent of the root -knot nematode (Meloidogyne arenaria) (Fallahzadeh-Mamaghani et al 2023).…”

Self-Assembled Amphiphilic Chitosan Nanomicelles: Synthesis, Characterization and Antibacterial Activity

“…The effects of CS, CS-DA, and CS-DA-SA on the morphology of E. coli and S. aureus were observed by SEM. As described [40] with some modifications, 3 mL of bacteria in stable or late-logarithmic growth were centrifuged (8000 rpm, 5 min), and the pelleted cells were fixed in 40 volumes of 2.5% glutaraldehyde at 4 • C for a minimum of 2 h. The bacteria were washed several times in a phosphate buffer and dehydrated (50, 70, and 90% ethanol). They were then resuspended in an ethanol tert-butanol solution (1:1, v/v) for 20 min.…”

Effect of Lyoprotective Agents on the Preservation of Survival of a Bacillus cereus Strain PBG in the Freeze-Drying Process

“…Additionally, other species such as B. sterothemophilus, B. megaterium, B. pumilus, B. licheniformis, and B. jeotgalim have shown bioremediation capabilities [28][29][30][31], producing various secondary metabolites such as lipopeptides, polypeptides, macrolides, fatty acids, polyketides, and isocoumarins, which enable them to decontaminate soils polluted with toxic metals and organic pollutants [32]. Bacillus cereus, in particular, has been employed in various studies to break down toxic metals [33][34][35], hydrocarbons [36,37], free cyanide [38,39], pesticides [40,41], and polypropylene [42]. Given its broad applicability in bioremediation processes [43,44], unique biotechnological properties [20][21][22], involvement in the microbiota of contaminated soils, and tolerance for free cyanide, it is crucial to address the preservation of Bacillus cereus [45].…”