Heavy Metal Toxicity in Bioremediation

This research employed a variety of microscopy and spread plating techniques to observe the effects of heavy metal treatments on a toluene-selected bacterial population. Microbial colonies were cultured on spread plates and the resulting numbers were compared to respiration data. The mechanisms of reproduction were demonstrated to be more sensitive to metal treatments than were the mechanisms of respiration. Phase contrast, Gram stain, fluorescent microscopy, were used to compare and document a wide variety of bacteria resulting from different metal treatments as well as from environmental changes within the source bioreactor. The removal of sensitive bacteria and the selection of metal tolerant species resulting from metal treatments was observed. Species that were initially unobserved within the bioreactor appeared to dominate when competing types of bacteria were removed and more agreeable environmental conditions were present. The use of fluorescent stains to differentiate between live and dead bacteria when treated with heavy metals proved to be impractical as the bacteria exhibited auto-fluorescence. Such new findings, however, did aid in the characterization of different types of bacteria and offered new techniques for potential heavy metal toxicity measurements as well as differentiation methods.