Effects of Cu on Soil Bacterial Number, Activity, and Community Structure as a Function of Time

Abstract

Microorganisms are a critical component in determining the availability of nutrients in soil. Diversity of the soil microflora provides stability, as a more diverse flora will cycle nutrients over a potentially more diverse set of environmental conditions Contamination of the soil by heavy metals has been shown to adversely affect soil microorganisms and cause a decrease in diversity and activity, affecting the production of plant available forms of nutrients and thus decreasing soil quality. This study measured the effects of Cu pollution on microbial activity, number, and diversity as a function of time since exposure to Cu. Microbial communities were sampled from soil microcosms containing 0,12.5, 25, and 50 mM Cu. In this study, certain species of bacteria were able to adapt to the Cu pollution resulting in a shift of bacterial community structure over time. Furthermore, microbial activity decreased after initial exposure to Cu, but increased in activity as exposure progressed with time. Soil with higher concentrations of Cu had higher proportions of the total bacterial population that were tolerant of Cu and the tolerance increased over time. RISA gel analysis revealed differences in community structure between soils containing different amounts of Cu pollutant as well as changes within the community as exposure to Cu increased with time.