Heavy Metal Resistance in Microorganisms Isolated from Waste Dumpsites in Uyo Metropolis, Nigeria

Abstract

Waste dumpsites often act as reservoirs for diverse microorganisms and toxic heavy metals, thereby posing serious environmental and public health challenges. Continuous disposal of municipal and domestic wastes promotes the accumulation of heavy metals in soils, which can influence microbial diversity and encourage the development of resistance mechanisms. Understanding the resistance patterns of microorganisms inhabiting waste-impacted soils is therefore essential for evaluating ecological risks and improving waste management practices. This study investigated the heavy metal resistance of microorganisms isolated from waste dumpsites in Uyo metropolis using standard microbiological and analytical techniques. Soil samples were collected and analyzed for physicochemical parameters, including temperature and pH. Microbial populations were enumerated using appropriate culture media, while bacterial and fungal isolates were identified through morphological and biochemical characterization. The resistance of the isolates to selected heavy metals was assessed using varying metal concentrations. Results showed that the mean temperature and pH of the dumpsite soils ranged from 26–37 °C and 6.8–8.7, respectively. Total bacterial counts ranged from 4.70 × 10³ to 5.60 × 10³ CFU/g, while fungal counts ranged from 1.86 × 10³ to 2.13 × 10³ CFU/g. Bacterial isolates included Bacillus, Escherichia coli, Pseudomonas, Corynebacterium, Klebsiella, Proteus, Aeromonas, Micrococcus, and Staphylococcus aureus, while fungal genera comprised Fusarium, Aspergillus, Penicillium, Mucor, and Rhizopus. Pseudomonas and Escherichia coli were the most predominant bacterial isolates (16.87%), whereas Rhizopus was the most frequent fungal isolate (28.25%). All isolates exhibited varying levels of resistance to heavy metals (0.50–2.50 mg/L). The findings indicate that waste dumpsites harbor heavy metal resistant microorganisms, highlighting the need for proper waste segregation, recycling, and environmental monitoring to reduce contamination and associated health risks.