Faculty & Staff Directory

Aaron Baxter

Photo of Aaron Baxter

Email
baxteraa@gvsu.edu

Title
Associate Professor

Office
313 Henry Hall

Phone
616-331-2888

Fax
616-331-2090

Office Hours

See available times here, or by appointment.

Courses Taught

BMS 212 - Introductory Microbiology
BMS 213 - Microbiology Lab
BMS 412 - Medical Bacteriology
BMS 413 - Medical Bacteriology Lab

Education/Training

Ph.D. (Genetics) University of Iowa, 2003
M.S. Department of Poultry Science, University of Arkansas, 1997
B.S. (Microbiology), Idaho State University, Pocatello, Idaho, 1994

Research Interests

Much of what occurs in science revolves around doing research. Research answers the questions of how something works often leading to applications that help our world. Examples showing either the eradication and/or control of many devastating diseases illustrate how an understanding of the mechanisms of pathogenesis leads to ways of fighting a disease.

My research has revolved around understanding the pathogenic mechanisms of Salmonella. The genes involved in Salmonella pathogenesis are found in specific areas known as pathogenicity islands. These islands contain a large number of genes involved in the formation of the type III secretion system, which is vital for bacterial invasion of intestinal cells to occur. The focus for my research has been on the regulatory genes that control activation and repression of the invasion genes. These efforts identified a repressor known as hilE. I began my analysis by mapping the hilE regulator to the chromosomes of serovar Typhimurium and serovar Typhi. My efforts placed the hilE gene at centisome 98. Analysis of this region revealed a ~40 kb region that was specific to Salmonella serovars. This region on closer inspection had many of the characteristics seen in the other pathogenicity islands found in Salmonella. The only other gene that has been identified in this region of the Salmonella genome is the iicA gene (induced intracellularly A gene) a gene shown to be induced upon Salmonella internalization into host cells. This evidence led to identifying this region of the Salmonella genome as a potentially new Salmonella Pathogenicity Island.

Since its identification, work has not been forwarded toward characterizing the other open reading frames within this region. My research is concerned with making a series of nonpolar mutations utilizing a technique by Datsenko and Wanner. The effects of these mutations can then be characterized utilizing lacZ reporters cloned into other regulatory genes such as hilE and hilA. Additional experiments for characterizing these mutations effect on SPI-1 function could be done utilizing cell invasion assays, macrophage survival assays and bacterial adherence assays. Any effects on Salmonella invasion could then be further characterized by identifying how each of the mutations leads to changes in Salmonella invasion in response to environmental signals.

An advantage to this line of research is that the data accumulated from these studies could be extended to other organisms that utilize a type III secretion system. My interests are to identify regulatory genes that respond to various environmental signals that directly upregulate or repress the expression of the type III secretion system. Regulation of these operons are important since there are many genes involved in encoding the secretion system. Therefore it is beneficial to the bacterium to regulate the expression of this system until it has reached an environment where increased gene expression is beneficial to the organism.

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