German Lorenzo-Vargas

German Lorenzo-Vargas

University of Puerto Rico - Mayaguez

Industrial Biotechnology & Biology


Mentor: Frank Caccavo, Jr., Ph.D., Assistant Professor of Microbiology

A Study of the Survival Growth Activity, and Population Dynamics of Dissimilatory Metal-Reducing Bacteria in Aquifers Microcosms

The Dissimilatory Metal-Reducing Bacteria (DMRB) metabolism represents a potential method for the bioremediation of subsurface environments. The DMRB organisms gain energy to support anaerobic growth by coupling the oxidation of hydrogen, organic acids, aromatics hydrocarbons or long-chain fatty acids to the reduction of variety of heavy metals including iron, manganese, cobalt, uranium, technetium, arsenic, selenium and chromium. The versatile metabolism of Shewanella alga, the DMRB model studied, indicates that it can be used to generate biologically active redox-reactive zones in the subsurface to treat groundwater and contaminated soils, through the immobilization, detoxification or precipitation of reduced metals species under anoxic conditions.

The object of this research is to investigate the potential of an inoculated organism to survive and compete with indigenous bacteria and efficiently carry out the reduction of ferric iron in situ. Subsurface material was obtained from Hanford site in Washington State, and this material was used to make the anaerobic aquifer microcosm. Once all the microcosms were inoculated with Shewanella alga, they served as effective ecosystem models. These models are used to study the competitiveness of DMRB inoculum for indigenous organic substrates and the effect of the inoculum in the indigenous microbial populations. The survival of this organism is monitored by plate counts on selective medium and the microbial communities are profiled by molecular techniques. The iron reduction potential rate is obtained through the measurement of Fe+2 concentration by using a colorimetric assay and spectrophotometer. The completed analysis will help us better understand the ecology, biochemistry, and physiology of these bacteria, and ultimately will be applied in bioremedial and industrial technologies.

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