Date of Award


Degree Name

Master of Science


Biological Sciences

First Advisor

Dr. Maria E. Scott

Second Advisor

Dr. Silvia Rossbach

Third Advisor

Dr. Susan Stapleton

Access Setting

Masters Thesis-Campus Only


To examine the secreted protein profile of Shiga toxin-producing Escherichia coli (STEC) we developed a method to enrich for low abundance secreted proteins. Rotary evaporation in combination with conventional spin column concentration achieved protein enrichment 10-fold greater than that acquired by the traditional trichloroacetic acid protein precipitation method. Analysis of the enriched secreted protein fraction led to the discovery of a protein designated as YghJ. Genetic homology analysis revealed that YghJ is a serine/threonine phosphatase-like protein. Serine/threonine phosphatases have not previously been discovered in Escherichia coli and are rare in bacteria. The probable serine/threonine phosphatase activity of YghJ suggests that the protein may play a role in the regulation of stress factors produced by E. coli during times of nutrient deprivation.