Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Nicholas Butzin


ClpXP, E. coli, Persistence, Queueing theory, Synthetic Biology, Tolerance


A major contributing factor to the abundance of antibiotic-resistant microorganisms and failed antibiotic treatment is survival due to antibiotic tolerance and persistence. Antibiotic tolerance is a widespread phenomenon that enables cells to survive treatment without carrying a resistance gene. This phenomenon renders antibiotic treatments less effective and facilitates antibiotic resistance. We are particularly interested in proteases, responsible for degradation of proteins, because of their known relationship to tolerance and persistence. Here, we examine the effects of proteases and antibiotic survival using queueing theory, in which one type of customer competes for processing by servers, that has traditionally been applied to systems such as computer networks and call centers. The biological queueing theory principally assumes that there are limited processing resources in a cell. Using synthetic systems engineered to form proteolytic queues, we can now examine tolerance/persistence in a new manner. In this work, we demonstrated in E. coli that the overproducing of protein engineered to be digested by the protease ClpXP can form a proteolytic queue, and this queue results in an increase in antibiotic tolerance ~80 and ~60 fold with ampicillin and ciprofloxacin, respectively. The proteolytic queue had no apparent effect on bacterial persistence levels. Furthermore, we showed that the queueing at the other two major proteases, ClpAP and Lon, have a slight effect on tolerant cell population.

Library of Congress Subject Headings

Drug tolerance.
Escherichia coli -- Effect of drugs on.
Drug resistance in microorganisms.
Pathogenic bacteria.
Queuing theory.



Number of Pages



South Dakota State University

Included in

Microbiology Commons



Rights Statement

In Copyright