Effect of Copper and Nickel on Soil Enzymatic Activities and Microbial Abundance and Diversity using Illumina MiSeq platforms

The objectives of this study were to determine the effects of nickel and copper on soil enzymatic activity and microbial communities in an environmentally controlled setting. Soil samples were treated with copper sulfate (1,300 mg kg-1) and nickel sulfate (1,600 mg kg-1). To determine the effect of Cu and Ni ions, potassium sulfate and water were used as controls and the treated soils were incubated for 100 days in a growth chamber. Nine enzymes were targeted including beta-glucosidase (BG), cellobiohydrolase (CBH), beta-N-acetylglucosaminidase (NAGase), aryl sulfatase (AS), acid phosphatase (AP), alkaline phosphatase (AlP), glycine aminopeptidase (GAP), leucine aminopeptidase (LAP), and peroxidase (PER). Surprisingly, only potassium sulfate used as a salt control induced a significant increase of the glycine-aminopeptidase (GAP) enzyme. The Illumina MiniSeq Platform was used to measure bacterial and fungal abundance and diversity. Candidatus Koribacter was the most abundant genus representing 27.6% of all bacterial genera followed by Chthoniobacter (7%), Granulicella (6.6%), and Acidobacterium (5.8%). For fungi, Russula and Tricholoma (13.4%) were the most prevalent genera followed by Hydnum (10.4%) and Cuphophyllus (8.8%). There was a significant reduction of relative abundance of the top five most abundant genera induced by copper ions compared to potassium sulfate and water. Copper also decreased significantly the levels of Amplicon Sequence Variants (ASV) and Shannon Diversity Index values for both bacteria and fungi. The effects of Ni on these indices were not significant compared to controls. Beta diversity analysis revealed no clear grouping or clustering based on treatments for both bacteria and fungi