Biological Sciences

Second Major



Jodi L Camberg

Advisor Department

Cell and Molecular Biology


Paul S Cohen

Advisor Department

Cell and Molecular Biology




Persistence; RpoS; urinary tract infection; toxin-antitoxin; cell dormancy


Persister cells are a subpopulation of bacteria that demonstrate high tolerance to antibiotics, but revert to sensitivity after antibiotics are removed. The mechanism for induction of the persister cell state and antibiotic tolerance is not completely understood but likely occurs through the establishment of dormancy. Some of the suggested mechanisms for persister cell formation in Escherichia coli include: toxin­-antitoxin systems, starvation, gene regulation by (p)ppGpp, and stochastic formation. In our study we examine the mechanisms behind persistence in the E. coli strain CFT073, a uropathogenic isolate, which forms elevated levels of persisters compared to the laboratory strain MG1655. However, CFT073 lacks many of the type II toxin­-antitoxin pairs associated with modulating persister cell formation. In addition, global stress response is impaired in the CFT073 isolate used in these studies, since it contains a five base pair insertion in the rpoS gene, which encodes RpoS, the master regulator of the global stress response. This insertion results in the expression of truncated RpoS. We compared several CFT073 strains mutated at the rpoS locus for the ability to form persister cells, as well as a strain deleted for Lon, a protease important for modulating toxin­-antitoxin function. To identify additional regulators of persister cell formation in CFT073, we performed minitransposon mutagenesis to isolate mutant strains, and screened mutants for persister cell formation. As many pathogenic bacterial species, including CFT073, cause recalcitrant infections attributable to persister cell activity, these studies will identify additional mechanisms underlying the development of bacterial persistence in these organisms.

Included in

Bacteria Commons