Date of Award


Degree Name

Doctor of Philosophy


Interdisciplinary Health Sciences


Delfina C. Dominguez


Calcium ions (Ca2+) play an important role in eukaryote cell signaling and regulation of physiological functions. Although evidence of a similar role for Ca2+ in prokaryotes has been difficult to demonstrate, there is mounting evidence that Ca2+ acts as a cell regulator in bacteria. The purpose of this study was to investigate Ca2+ signaling and the effect of Ca2+ on gene expression of various multidrug resistant (MDR) efflux pumps and their regulator MgrA in Staphylococcus aureus and clinically isolated MRSA. We hypothesized that the presence of Ca2+ increased gene expression of multidrug resistance pumps, LmrS, NorA, and the regulator, MgrA. This hypoThesis was based on our previous evidence of unique intracellular Ca2+concentration signatures in response to various antibiotics and the enhancement of ethidium bromide efflux by Ca2+ in S. aureus. The effect of Ca2+ on efflux gene expression was evaluated by the addition of increasing concentrations of CaCl2, and the Ca2+ chelator, EGTA. Gene expression of the efflux genes and the regulator, MgrA were measured and compared to housekeeping genes, GMK and GyrA under the same conditions. Our results indicate that the presence of Ca2+ significantly enhanced gene expression of MDR efflux genes as compared to untreated and EGTA treated cells. The results indicate that the presence of EGTA significantly decreased efflux gene activity as compared to untreated cells and Ca2+ treated cells. We conclude that Ca2+ may be a signaling molecule for the regulation of gene expression of efflux in S. aureus. Transcriptomic studies are needed to determine the proteins involved in potential calcium transduction pathways for genetic regulation of efflux in S. aureus




Received from ProQuest

File Size

108 p.

File Format


Rights Holder

Amy Rebecca Nava