Date of Award


Degree Type

Honors College Thesis


Biological Sciences

First Advisor

Mohamed Elasri, Ph.D

Advisor Department

Biological Sciences


The msaABCR operon regulates virulence factors in Staphylococcus aureus, a Gram-positive commensal organism that colonizes healthy individuals but can also be a human pathogen. These virulence factors include biofilm development, pigmentation, and extracellular protease production. The operon consists of the msaB gene, which produces a coding transcript, the msaA gene and the msaC gene, which produce noncoding RNAs, and msaR, which produces an antisense RNA. The latter three transcript regions of the operon are referred to as untranslated regions (UTRs) and are essential for the function of the operon, but only msaB encodes a protein. The mechanism of regulation by which these individual genes from the operon contribute to MsaB production and regulate virulence factors is still unknown. The purpose of this study is to find the region of the msaABCR transcript that is required to regulate virulence factors. Truncated complement constructs were made with altered versions of the 5’ msaA region or the 3’ msaC region to determine which sections of the transcript are necessary to produce virulence phenotypes. Various assays were conducted using these constructs to determine the effect of the alterations on biofilm formation, protease production, and pigmentation. This was done by comparing the effects of the constructs to the wild type strain, msaABCR mutant strain, and msaABCR complemented strain. These results could contribute to the discovery of the regulatory mechanisms of the msaABCR operon, which is a critical component in preventing and treating S. aureus infections. The results showed that the 5’UTR (msaA) and 3’ UTR (msaC) region of the operon transcript are required for its full function in regulating virulence and biofilm development in S. aureus. However, we still do not know the exact mechanism by which UTR regions contribute to the regulation and functioning of msaABCR operon and/or MsaB production (Sahukhal & Elasri, 2014).

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