Date of Award


Degree Type


Degree Name

Master of Science


Microbiology and Immunology


Dr. Thomas Linn


The Gram-positive and ubiquitous bacterium Bacillus cereus is an emerging human and animal pathogen, and is capable of adapting to numerous extracellular stresses such as the low pH environment of the gastrointestinal tract. One mechanism B. cereus might utilize to regulate the acid-tolerance response system is through alternative sigma factors: proteins that bind and direct RNA polymerase to promoter- specific genes. A previous study found that alternative sigma factors c5816 and o7615 were induced dramatically at low pH, but it was unclear whether these sigma factors mediated an acid-tolerance response. Here, molecular tools were developed to further study these a factors, including a regulatable expression system and sigma-specific polyclonal antibodies. We were unable to identify a growth-deficient or growth- enhanced phenotype in strains that had these sigma factors deleted or could over-express these sigma factors, respectively. Through transcriptome analysis and qRT-PCR, we attempted to define the a5816 regulon. The proteolytic subunit of a Cip protease, ClpA, was found to potentially be part of the a5816 regulon. Understanding how B. cereus uses sigma factors to adapt to environmental stresses may give insight on how this emerging pathogen interacts and survives in its host.



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