Associate Professor
My research focuses on the pathogenic mechanisms of Salmonella and biofilm formation in Escherichia coli. In Salmonella we are currently working toward finding additional genes necessary for Salmonella virulence. Studies have shown that the genes involved in Salmonella pathogenesis are found in specific regions of the chromosome known as pathogenicity islands. Salmonella Pathogenicity Island 1 (SPI-1) has numerous genes involved in the formation of a type III secretion system and other secreted effector proteins. Activation of this island allows for bacterial invasion of intestinal cells. A second critical island (SPI-2) is needed for survival within macrophage after invasion across the intestinal epithelia is completed. Due to the number of genes required for each of these processes to occur, the bacteria tightly regulate their expression. Our lab’s focus is on the regulatory genes that control activation and repression of these islands in response to environmental signals. As part of these studies, I characterized a repressor known as hilE, which represses the activation of SPI-1. Studies of the DNA sequence surrounding hilE suggest that this repressor lies in a 40 kb region of the chromosome that has all the hallmarks of a pathogenicity island, yet little is known about the function of these genes. We created ten different polar mutations in potential operons within this identified region. Work has started trying to analyze the effects these mutations have on Salmonella virulence by using gene reporters, cell invasion, macrophage survival and bacterial adherence assays, etc. all conducted under various virulence inducing and noninducing environmental conditions. Any effects on Salmonella invasion could then be further characterized by identifying how each gene affects Salmonella pathogenesis in response to an environmental signal.
My second project is looking for genes important for Escherichia coli biofilm formation under conditions that mirror the intestinal environment. Earlier work has identified many genes needed for the activation and formation of a biofilm when the bacteria are grown under aerobic conditions. As E. coli is a commensal bacteria found in the anaerobic conditions of the colon, we are trying to find regulator genes that may be responsible for increasing or decreasing biofilm formation in response to oxygen concentration. We developed a biofilm assay and are using it to screen a library of nonpolar mutants under aerobic, microaerophilic, and anaerobic conditions to determine if there are effects on biofilm formation at varying oxygen levels.
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About Aaron Baxter
My research focuses on the pathogenic mechanisms of Salmonella and biofilm formation in Escherichia coli. In Salmonella we are currently working toward finding additional genes necessary for Salmonella virulence. Studies have shown that the genes involved in Salmonella pathogenesis are found in specific regions of the chromosome known as pathogenicity islands. Salmonella Pathogenicity Island 1 (SPI-1) has numerous genes involved in the formation of a type III secretion system and other secreted effector proteins. Activation of this island allows for bacterial invasion of intestinal cells. A second critical island (SPI-2) is needed for survival within macrophage after invasion across the intestinal epithelia is completed. Due to the number of genes required for each of these processes to occur, the bacteria tightly regulate their expression. Our lab’s focus is on the regulatory genes that control activation and repression of these islands in response to environmental signals. As part of these studies, I characterized a repressor known as hilE, which represses the activation of SPI-1. Studies of the DNA sequence surrounding hilE suggest that this repressor lies in a 40 kb region of the chromosome that has all the hallmarks of a pathogenicity island, yet little is known about the function of these genes. We created ten different polar mutations in potential operons within this identified region. Work has started trying to analyze the effects these mutations have on Salmonella virulence by using gene reporters, cell invasion, macrophage survival and bacterial adherence assays, etc. all conducted under various virulence inducing and noninducing environmental conditions. Any effects on Salmonella invasion could then be further characterized by identifying how each gene affects Salmonella pathogenesis in response to an environmental signal.
My second project is looking for genes important for Escherichia coli biofilm formation under conditions that mirror the intestinal environment. Earlier work has identified many genes needed for the activation and formation of a biofilm when the bacteria are grown under aerobic conditions. As E. coli is a commensal bacteria found in the anaerobic conditions of the colon, we are trying to find regulator genes that may be responsible for increasing or decreasing biofilm formation in response to oxygen concentration. We developed a biofilm assay and are using it to screen a library of nonpolar mutants under aerobic, microaerophilic, and anaerobic conditions to determine if there are effects on biofilm formation at varying oxygen levels.
| Present | Associate Professor, Grand Valley State University ‐ Biomedical Sciences | |
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Disciplines
Research Interests
Courses
- BMS 212 - Introductory Microbiology
- BMS 213 - Microbiology Lab
- BMS 412 - Medical Bacteriology
- BMS 413 - Medical Bacteriology Lab
- BMS 422 - Bacterial Physiology
- BMS 423 - Bacterial Physiology Lab
| 2003 | Ph.D., University of Iowa ‐ Genetics | |
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| 1997 | M.S., University of Arkansas ‐ Poultry Science | |
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| 1994 | B.S., Idaho State University ‐ Microbiology | |
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Contact Information
Office: 313 Henry Hall
Phone: (616) 331-2888
Email: baxteraa@gvsu.edu
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