Abstract Description

Heavy metal (HM) contamination in soils poses a significant threat to the ecosystem and public health. Yet, it offers a unique opportunity to explore the adaptive potential of microbial communities. The Insizwa Intrusion Complex, which straddles the Eastern Cape and KwaZulu Natal provinces of South Africa is a region characterised by high natural heavy metal soils such as Copper (Cu), Nickel (Ni), and Chromium (Cr). This study investigated the bacterial diversity and heavy metal tolerance of selected isolates inhabiting the heavy metal-rich soils from the eastern (E) and western (W) slopes of the Ngeli mountain. Collected soil samples,labelled (EA- EM, WA-WM), were analysed for HMs, and soil physicochemical properties. Soil DNA extracts were subjected to metabarcoding analysis to identify bacterial communities through the amplification of the hypervariable V4-V5 16S rRNA region using Illumina sequencing. Soil suspensions were cultured on media amended with varying concentrations of Cu, Cr and Ni. Selected HM-tolerant isolates were molecularly identified through Sanger Sequencing. The prevalent bacterial taxa included Proteobacteria, Planctomycetota and Acidobacteriota. Bacterial isolates displayed differential tolerance to each metal, highlighting microbial adaptation to the ultramafic soils in the region. Selected HM-tolerant bacterial isolates were identified as Pseudomonas sp. strain XJC-5, Pseudomonas moraviensis strain MJFC2 (P. moraviensis), Pseudomonas sp. strain 34B, Pseudomonas sp. strain 254.12 .The findings reveal that these microbial communities play a crucial role in the ecosystem by potentially aiding in heavy metal bioremediation and promoting sustainable soil health. This study underscores the importance of the soil microbiome in maintaining soil fertility, suggesting potential applications in bioremediation and sustainable agriculture in metal-rich environments.