An-Najah Staff

The effect of raw city wastewater irrigation on species richness and evenness of cycloheximide-resistant (CH) fungal community was studied in 13 field soils receiving either raw city wastewater or normal irrigation, and raw city wastewater in Nablus area, using the hair baiting (HBT) and surface soil dilution plating (SSDP) techniques. Three of these fields, one had been receiving raw city wastewater for more than ten years and designated heavily polluted field, and the other 2 were cultivated for the first time and were either irrigated with raw city wastewater (newly polluted field) or normal irrigation water (nonpolluted), were sampled 4-7 times over a 9-month period.
Fifty seven CH-resistant species belonging to 18 genera were recovered, of which 49 species were isolated from soil habitats and 28 species from raw city wastewater. The HBT had shown to be more efficient in the isolation of pathogenic and potentially pathogenic fungi including dermatophytes, a higher percentage of this group of fungi was recovered from the three main field soils studied using HBT (70% of all isolates recovered by this method), than the SSDP (35.5%). Two dermatophytes (Microsporum gypseum, and, Trichophyton ajelloi), and five dermatophyte related fungi (Arthroderma cuniculi, A curreyi, Chrysosporium keratinophilum, C. tropicum, and C. pannorum) were recovered from these habitats, no dermatophytes were recovered by the SSDP method.
Wastewater irrigation seems to affect fungal population densities, with the highest population densities being found in the heavily polluted field soil, while lower population densities were found in the nonpolluted field soil. Increases in organic matter were also observed as a result of sewage effluents irrigation.
However, basic similarities in the biodiversity of CH-resistant fungal communities existed in nonpolluted and polluted field soils, and raw city wastewater. Comparable number of fungal species were recovered from the three main field soils, with the species most commonly found in these habitats included: Alternaria alternata, Aspergillus candidus, Geotrichum candidum, and Paecilomyces lilacinus.
The ability of 55 CH-resistant fungal species (117 isolates), to degrade human hair in vitro was investigated. The intensity of keratinolytic activity (IKA) was estimated on a scale of 0-100, based on morphological expression of keratinolysis. A high percentage of the species tested (48/55, 87%) demonstrated varied degrees of keratinolytic activity. Five species (Chrysosporium keratinophilum, Microsporum gypseum, Penicillium frequentans, Rhizopus stolonifer, and Trichophyton ajelloi) showed strong IKA, and were capable of producing invasive structures related to radial penetration and surface erosion contemporaneously. On the other hand, seven of all tested species showed no keratinolytic activity including: Acremonium species, Aspergillus carneus, Nectria inventa, Penicillium citrinum, Paecilomyces variotii, Plectosphaerella cucumerina, and Verticillium nubilum. Isolates of the same species can vary in their IKA,s. Thus such character does not seem to be a constant or species-specific character.
Field soils receiving either raw city wastewater or normal irrigation water, were shown to be rich in pathogenic and potentially pathogenic CH-resistant fungi, including dermatophytes, with raw city wastewater yielding the highest percentage (81%), followed by the newly wastewater irrigated field (77.7%), the nonpolluted field (67%), and the heavily polluted field (63.4%). Hygienic measures should therefore be taken to control the spread of these fungi in the environment of human communities, and to avoid mycotic infections among farmers.