The Effects of Soil Copper Concentration on the Activity and Diversity of Microbial Communities

Abstract

Bacteria are an essential component of soil ecosystems, assisting in nutrient cycling and degradation of organic materials that maintain a healthy environment for growth of plants and other microorganisms. Stable levels of bacterial activity and diversity are indicative of a fully functional environment. Contamination with heavy metals, including copper, has been shown to adversely affect stability of soil microcosms through reduction of bacterial activity and diversity. Therefore, research was conducted to measure the microbial activity in soils a year after contamination with 0, 12.5, 25, and 50 mM copper using arginine ammonification and dehydrogenase activity assays. Also, bacterial diversity was examined through the extraction, cloning, and sequencing of DNA fragments from the bacterial 16s ribosomal gene. The sequences obtained were matched to accession numbers to determine the number of unique sequences. The sequences were aligned and used to construct phylogenic trees. It was concluded that: 1. a marked decrease in activity resulted from increased copper contamination, 2. in soils with higher levels of copper contamination, a larger percentage of the soil community was copper tolerant and 3. bacterial diversity was not significantly affected in overall number of unique sequences; however, small changes were exhibited in bacterial community structure.