Isolation and identification of Aspergillus species isolated from different soil environments in Jos Metropolis, Plateau State, Nigeria

Abstract

Aspergillus species are among the most ubiquitous filamentous soil fungi and play significant ecological, industrial, and medical roles. However, some species are opportunistic pathogens and producers of harmful mycotoxins, making their occurrence in environmental soils a public health concern. This study aimed to isolate and identify Aspergillus species from different soil environments within Jos Metropolis, Plateau State, Nigeria, and to determine their distribution across selected anthropogenic habitats. A total of 30 soil samples were collected in triplicate from ten sampling locations representing gardens, cultivated lands, mechanic workshops, industrial waste sites, industrial effluent areas, abattoirs, and vegetable oil-contaminated soils. Fungal isolation was carried out using the serial dilution pour-plate technique on Potato Dextrose Agar supplemented with chloramphenicol. Pure cultures were obtained through repeated subculturing, while identification was based on cultural and microscopic characteristics using standard taxonomic keys. Thirty-six Aspergillus isolates representing four species were recovered. Aspergillus niger was the predominant species, accounting for 15 (41.7%) isolates, followed by A. fumigatus with 13 (36.1%), A. flavus with 7 (19.4%), and A. nidulans with 1 (2.8%). Cultivated soils and industrial effluent sites recorded the highest proportion of isolates (19.4% each), whereas mechanic workshop and oil-contaminated soils yielded comparatively fewer isolates. The predominance of A. niger suggests its superior ecological adaptability and ability to thrive in soils enriched with organic matter, while the occurrence of A. fumigatus and A. flavus highlights the potential public health risks associated with exposure to opportunistic and mycotoxin-producing fungi. The study concludes that soils from different environments within Jos Metropolis constitute important reservoirs of diverse Aspergillus species, with their distribution largely influenced by environmental conditions and anthropogenic activities. Continuous environmental surveillance and the incorporation of molecular identification techniques are recommended to improve species characterization and support environmental, agricultural, and public health management.

Keywords: Aspergillus species, soil fungi, Aspergillus niger, fungal isolation, Jos Metropolis, environmental microbiology.

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