Isolation, identification, and characterization of heavy metal-resistant bacteria from soil samples collected at a cement company in Nigeria.

Many heavy metals, including cadmium, chromium, copper, lead, and zinc, are produced during cement-making. Even in low quantities, most of the heavy metals released are known to be harmful to plants and animals. The objective of this study was to isolate, identify and characterize heavy metal-resistant bacteria from soil samples collected at Benue Cement Company, Nigeria. Soil samples taken near the Gboko facility of Nigerian cement manufacturer Benue Cement Plc were tested for heavy metal-resistant bacteria. Results from the study revealed that compared to other metals (Pb, Cr, and Cd), the concentration of copper and zinc was consistently quite high across all sites. The levels of all components examined were determined to be higher than the limits allowed by the World Health Organization In this study, Cd, Zn, Cr, Cu, and Pb were found in soil samples taken from the Benue cement industry, according to the analysis of heavy metals. The results obtained from this study further revealed that out of 20 isolates only five (5) bacterial isolates, namely Staphylococcus aureus, Escherichia coli, Proteus sp., Bacillus cereus, and Lactobacillus which showed high levels of heavy metal resistance were selected for further studies in secondary screening. Based on the biochemical tests, S. aureus reacted positively to catalase and coagulase test. They were also seen to ferment lactose, sucrose and glucose. The E. coli reacted negatively to citrate, catalase, coagulase tests, and did not ferment sucrose. However, the bacteria fermented lactose and glucose. Lactobacillus reacted positively to only citrate but fermented the three sugars. Proteus sp. fermented glucose and sucrose and also reacted positively to citrate, catalase and urea tests. The B. cereus fermented glucose and sucrose. The bacteria also reacted positively to only citrate and catalase tests. Results of showed that S. aureus had MIC values between 12 and 16 mg/L, E. coli between 20 and 50 mg/L, Proteus species between 15 and 64 mg/L, and B. cereus between 10 and 18 mg/L, all against various metals. The B. cereus showed the lowest resistance to several heavy metals, while E. coli showed the highest resistance. Additionally, E. coli demonstrated a significant resistance level to all ten antibiotics examined. Antibiotic resistance was highest in E. coli and lowest in Proteus species. The findings of this study revealed that the four isolates that showed high tolerance to heavy metals could be used as inoculants to bioremediate cement sites that polluted by heavy metals. [ABSTRACT FROM AUTHOR]