Influence of soil lead (Pb) levels on fungal occurrence, growth and sporulation

Abstract

The emission of exhaust fumes into the environment, which are eventually deposited in to soils, contributes to the increasing hazardous levels of lead in the soil ecosystem. Kenya has a high number of automotives that emit high levels of exhaust fumes that make lead a major environmental pollutant. At high levels, lead has adverse effect on the soil microbiota. This study was designed to investigate the effect of lead on mucoraceous fungi in a roadside habitat. Mucoraceous fungi are mostly saprophytes and play an important role in nutrient cycling, elemental storage and transport in the soil. Soil plate and dilution methods were used to isolate fungi from the topsoil collected from the Kiambu roadside habitat and forest stand. The soil lead content was determined by atomic absorption spectrometry. The effect of lead on the occurrence, growth and sporulation of the fungi was studied. Lead concentration of up to 160 μg g-1 was recorded from the roadside, habitat soils. This decreased with increase in distance away from the road. The mucoraceous fungi showed a decline in frequency of occurrence and species diversity with increasing lead pollution load in the soil. However, Cunninghamella spp. were predominantly present in the heavily contaminated soils and showed good in vitro growth in lead agar medium. Cunninghamella. elegans, which was the most common species showed tolerance for lead. Theses results showed that lead negatively affected the occurrence and diversity of mucoraceous fungi. The presumed tolerance of lead by species of Cunninghamella presents them as candidates for use in remediation of contaminated soils.