The Effect of Heavy Metal Pollution on Copper Tolerance and Antibiotic Resistance of Soil Bacterial Communities

Abstract

The bacterial composition of soils is important in the study of ecosystem ecology. Soil bacteria are involved in nutrient cycling, soil nutrition, and degradation of organic matter, and provide a healthy environment for plants and other microorganisms. Contamination of the soil by heavy metals has been shown to have adverse effects on the bacterial communities living in soil. Heavy metals can cause shifts in pH, providing an unstable environment for many species ofbacteria. Also, it is quite common for the genes for resistance to heavy metals and for antibiotic resistance to be found together on a plasmid, therefore, conferring resistance to both metals and antibiotics to the bacteria. In this study, I measured the composition ofbacterial communities in soils collected from sites near the drainage area of the Anaconda Copper Mining Company which caused contamination of soils in the Clark Fork River Valley in and around Deer Lodge County, MT. Using pH, dehydrogenase activity, antibiotic resistance, and DGGE, I was able to conclude the following: 1) soils with high levels of Cu2+ had a low pH, 2) studied soils with low pH also had low biological activity, 3) total viable bacteria were significantly correlated with pH and Cu2+ availability, and 4) species richness of the antibiotic resistant bacterial community showed no specific effects of Cu2+ or pH.