Exploring Oscillatory Dynamics through Extension of Cross
Protection Mutualism to a Susceptible Bacterial Colony
Evelyn Brown / ebrown3@bellarmine.edu / Faculty
Advisor: Caroline Doyle
Understanding how bacterial populations survive antibiotic
exposure has clinical and ecological relevance, yet the implications of
cooperative antibiotic deactivation on the population and evolutionary
dynamics, particularly in the presence of more than one antibiotic, remain
poorly understood. Our study evaluates the preservation of a susceptible bacterial
species in the presence of two Escherichia coli strains that have been shown to
form successful cross-protection mutualism in the presence of ampicillin and
chloramphenicol. The ampicillin resistant strain is a result of a plasmid
constructed utilizing a modular multi-part DNA assembly technique in which
start and stop codons were exploited as fusion sites (promoter J23116, RBS
(RBSc42), and terminator L3s2p55 were cloned into a start-stop plasmid
pStA0::eyfp). The ampicillin plasmid caries a gene that encodes the β-lactamase
enzyme which allows for deactivation of the extracellular space and in theory
could extend that protection to allow a sensitive species to survive. The
chloramphenicol resistant strain is a result of a plasmid that encodes for the
chloramphenicol acetyltransferase enzyme which deactivates chloramphenicol
within the cell. Although the enzymatic deactivation of chloramphenicol occurs
internally, perhaps diffusion between the medium and the cell interior may
decrease the extracellular concentration of chloramphenicol so that a
susceptible species can survive. Given that each strain has the capability of
conferring protection to the other species in a multidrug environment, it is
hypothesized that a vulnerable species could also reap the benefits of
enzymatic deactivation.
Recipient of the Student Government Association Research Grant
Award