Department of Microbiology - Faculty

The Achenbach Lab specializes in microbial genetics and bioremediation. Our overall goal is to study the genetics of soil microorganisms that are able to metabolize harmful substances or indirectly transform contaminants (i.e. humics oxidation, perchlorate reduction, benzene oxidation, iron oxidation, and uranium reduction) in hopes of finding long-term natural solutions for environmental remediation.

From left: Nastassia Jones, Gareth McGee, Stacey Taft, Rikhi Gon,
Dr. Laurie Achenbach, O.J. Duncan, and Ming Gao.


	Stacey Taft: The goal of my project is to identify genes that are involved in ferrous iron (Fe²⁺) oxidation, a metabolism carried out by the soil bacterium Dechloromonas aromatica strain RCB. Contrary to iron oxidation reactions carried out by acidophilic or phototrophic bacteria, this particular metabolic process is anaerobic, occurs at neutral pH, and does not rely on light. Iron oxidation (Fe²⁺ to Fe³⁺) is important for many reasons; it is a natural occurrence in the earth's crust and contributes to biogeochemical cycling, and iron minerals are important to soil and sediment geochemistry. Iron oxidation is also the cause of rust and may even facilitate pipe corrosion underground. Most importantly, however, is the discovery of iron oxides (Fe³⁺) forming compounds with harmful radioactive isotopes, such as uranium. These radioactive contaminants, called radionuclides, are commonly found at abandoned mine facilities in the western U.S. and may spread to the groundwater, potentially contaminating drinking wells or downstream lakes and rivers. When soluble radionuclides interact with iron oxides, however, an insoluble mineral is formed, rendering it immobile and reducing the threat of contaminant spread. Therefore, it would be ideal to harness bacteria, ubiquitous in nature, to form iron oxides to block the spread of harmful contaminants. We propose that this form of bioremediation would be a clean, safe, and inexpensive way to clean the environment. Before we can even begin to utilize natural soil microorganisms for bioremediative techniques, however, we need to understand the genetics of this metabolism. I have been using a variety of molecular techniques in order to glean more information about the specific types of genes that are involved in iron oxidation and the potential role they play. Apart from my research, I really enjoy tennis and golf - I'm also officially addicted to Starbucks, Harry Potter, and the St. Louis Cardinals.

Rikhi Gon: Uranium-contaminated sites are present all around the world because of abundant mining and processing of the heavy metal during the cold war era. All compounds and isotopes of uranium (U) are toxic, teratogenic and radioactive. A proposed bioremediation strategy for uranium-contaminated sites is microbial reductive immobilization of the metal from soluble U(VI) to insoluble U(IV) phase. However, the presence of nitrate has been reported to inhibit and reverse the uranium reduction reaction. The goal of my research is to understand the mechanism of direct nitrate-mediated uranium re-oxidation. In order to study the genes and proteins associated with this reaction, I am using techniques like RNA Arbitrarily Primed PCR (RAP-PCR), microarray analysis and random transposon mutagenesis on uranium-oxidizing bacteria Diaphorobacter strain TPSY. Since nitrate is a major co-contaminant present at the DOE nuclear waste sites, the results of this study will enable the design of a 'model' bioremediation strategy for the permanent immobilization of reduced uranium, even in the presence of nitrate. I am also studying the genes induced under anaerobic benzene oxidizing condition in Dechloromonas aromatica strain RCB with nitrate as the terminal electron acceptor. I believe that microorganisms are the most inexpensive and environment-friendly tools that can be manipulated to clean up the environment. During my spare time (which is a rare luxury) I love watching movies and reading novels.

	Nastassia Jones: Humic substances (HS) are organic matter formed from the decomposition of plant, animal, and microbial remains in the environment. When studying the reduction-oxidation reactions of humics, it is apparent that nitrate-dependent humics oxidation is ubiquitous and, therefore, likely plays an important role in the environment. Additionally, HS bind both hydrophobic and hydrophilic compounds, interact with heavy metals, and may transfer electrons to contaminating metals by using the redox-reactive components, quinone moieties. My doctoral research project centers on microbial community analysis to understand the ubiquity and diversity of microorganisms capable of HS oxidization using Denaturing Gradient Gel Electrophoresis and identification of genes induced under humics oxidizing conditions by Random Arbitrarily Primed Polymerase Chain Reactions and Random Transposon Mutagenesis. Currently, as a NSF Heartland Ecological/Environmental Assistant Research Training Graduate K-12 (HEART GK-12) Resident Scientist, I spend my time not only in the laboratory, but also at Carbondale Community High School in Lena Dierks' science classroom. My high school research focuses on integrating technology into the classroom through web-based instruction and making science a FUN experience, thus increasing science literacy at the high school level. My passion centers on educating those who are socio-economically disadvantaged by focusing on gender and race equality as they relate to rural science education. The skills gained from research, teaching, and extracurricular activities at SIUC play a major part in the shaping of my personality, permitting me to make a great contribution in diversifying the university and community.

Ming Gao: My research concerns the identification of enzymes involved in the anaerobic benzene oxidation pathway. Dechloromonas strain RCB is the first reported anaerobic benzene oxidizer in pure culture that can completely oxidize benzene to CO₂ coupled with nitrate reduction. Using it as a model organism, I employ 2-dimensional protein gel electrophoresis to identify the gene products that are differentially expressed when RCB is grown with benzene versus other substrates as the sole electron donor. Finally I hope to generate a protein profile that will identify the corresponding genes in the RCB genome.

	Gareth McGee:

Student Workers: