Abstract

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Untreated abattoir wastewater contains high microbial loads that may persist in irrigated soils and transferred to edible crops. This study investigated the culture and molecular profiles of microorganisms isolated from abattoir wastewater, it’s irrigated soils and crops cultivated on the receiving soils with particular emphasis on soil and crop-associated microbiomes in Agbor, Delta State, Nigeria. Effluents exhibited elevated bacterial (6.94–7.02 log₁₀ cfu ml⁻¹) and coliform counts (5.38–5.52 log₁₀ cfu ml⁻¹), with isolation of Bacillus, Pseudomonas, Enterobacter, Escherichia coli, Aspergillus, and Penicillium species. Wastewater-irrigated soils demonstrated significantly higher microbial population than the control, including heterotrophic bacteria (up to 7.46 log₁₀ cfu g⁻¹) and enterococci (up to 5.08 log₁₀ cfu g⁻¹). Soil communities were dominated by Bacillus (100%), Pseudomonas (90%), Enterobacter (70%), E. coli (70%), and Aspergillus niger (100%). Crops grown on abattoir wastewater-irrigated soils harboured similar microbial groups, confirming effluent–soil–crop microbial transmission. Molecular characterization using 16S rRNA gene sequencing for bacteria and Internal Transcribed Spacer (ITS) sequencing for fungi confirmed the identities of key isolates, including Escherichia coli, Pseudomonas aeruginosa, Pseudomonas fluorescens, Enterobacter cloacae, Bacillus subtilis, Aspergillus niger, and Fusarium oxysporum. The findings demonstrate that irrigation with untreated abattoir wastewater alters soil microbiome and facilitates the transfer of wastewater-borne microorganisms onto edible crops, raising significant food-safety and public-health concerns.

Keywords: Abattoir wastewater, crop contamination, ITS sequencing, microbial profiling, microbiome, soil, 16S rRNA.