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Proteomics/Genomics Research Group
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Greenhouse
STEM
College of Science, Technology, Engineering & Mathematics
Proteomics/Genomics Research Group
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Dr. Jonathan Caguiat |
Research Interests
Survey of metal resistant bacteria from a mercury contaminated site
The Y-12 plant in Oakridge, TN processed uranium during World War II to make the first atomic bomb and lithium during the Cold War to make hydrogen bombs. These processes contaminated the nearby stream, East Fork Poplar Creek, with mercury and other heavy metals. Stenotrophomas maltophilia Oakridge strain O2 (S. maltophilia O2), which was isolated from East Fork Poplar Creek, grew in the presence of toxic levels of zinc, copper, platinum, mercury, gold, cadmium, lead, silver, chromium and selenium. Nine hundred aerobic bacterial colonies were isolated from a site contaminated with 96 ppm mercury, and one thousand six hundred other colonies were isolated from a downstream site contaminated with 2 ppm mercury. We are in the process using 16s rDNA to determine the identity of some of these colonies and are screening them for growth in the presence of toxic concentrations of mercury, copper, zinc, lead, cadmium, chromium and selenium. So far, we have tentatively identified multi-metal resistant species of Enterobacter, Pseudomonas, Microbacterium and Cupriavidus. The genes, which encode metal resistances in S. maltophilia O2, will then be identified using the polymerase chain reaction (PCR) and transposon mutagensis and used to identify similar genes in the other isolates by colony hybridizations.
Selenium Homeostasis in Enterobacter cloacae YSU
We have also been working with the strain, Enterobacter cloacae YSU (E. cloacae YSU), which is resistant to salts of mercury, cadmium, zinc, arsenic, copper, chromium, silver, gold and selenium. Selenium (Se) is an important element in the diet of all living organisms, but too much can be toxic. In the presence of high concentrations of selenite (SeO32-), a toxic form of selenium, E. cloacae YSU precipitates it from its culture medium by reducing it to elemental selenium (Se0). Thus, under high selenium concentrations, the bacterium must maintain a balance or homeostasis of the amount of selenite that is incorporated into the cell and the amount of selenite that is detoxified.
We used proteomics will to identify some of the proteins that may be involved in selenite homeostasis. E. cloacae YSU was grown in the presence and absence of 40 mM selenite. One hour after selenite was added, protein samples from each culture were separated by 2-dimensional gel electrophoresis. Comparing the intensity of protein spots on gels containing samples from bacteria grown in the presence of selenite with gels containing samples from bacteria grown in the absence of selenite identified proteins that were differentially expressed. These proteins were excised, digested with trypsin and identified by mass spectrometry at the Ohio State University. Preliminary results showed that the overexpressed proteins may be involved in relieving selenite-induced oxidative stress, in selenite reduction and in selenite efflux.
Selected Publications
Holmes, A., A. Vinayak, C. Benton, A. Esbenshade, C. Heinselman, D. Frankland, A. Kurtanich and J. Caguiat. Comparison of two multimetal resistant bacterial strains: Enterobacter cloacae UNK and Stenotrophomonas maltophilia ORO2. In preparation.
Jasenec, A., N. Barasa and J. Caguiat. Proteomic profiling of the selenite resistant strain Enterobacter cloacae UNK. In preparation.
Benton, C., N. Barasa and J. Caguiat. Proteomic profiling of the selenite resistant E. coli strain HB101(pOR1). In preparation.
Song, L., J. Caguiat, Z. Li, J. Shokes, R. A. Scott, L. Olliff and A. O. Summers (2003). Engineered Single Chain, Antiparallel, Coiled Coil Mimics MerR Metal Binding Site. J. Bacteriol. 186:1861-1868.
Caguiat, J. J., A. L. Watson and A. O. Summers (1999). Cd(II)-Responsive and Constitutive Mutants Implicate a Novel Domain in MerR. J. Bacteriol. 181:3462-3471.
Jackson, J. H., R. George, H. O. Adeyemi, M. A. Winrow, P. A. Herring, J. J. Caguiat, C. F. Mulks, R. Srikanth, S. H. Harrison and R. E. Mickens (1998). Characterization of Base Coding Periodicities in Protein-Coding Genes. J. Biol. Sys. 6:49-70.
Frasch, W.D., J. Green, J. Caguiat and A. Meija (1989). ATP Hydrolysis Catalyzed by a œ-Subunit Preparation Purified from CF1oCF0. J. Biol. Chem. 264:5064-5069.
Summers, A. O. and J. Caguiat (2004). Metal Binding Proteins, Recombinant Host Cells and Methods. Patent Number 6,750,042.