Date of Award

Spring 5-8-2017

Document Type


Degree Name

Bachelor of Arts



First Advisor

Joan Slonczewski

Second Advisor

Hewlet McFarlane


Escherichia coli mutants evolved in benzoate (up to 20mM) show increased minimum inhibitory concentrations (MIC) for the antibiotics chloramphenicol and tetracycline (1). Salicylate, an aromatic acid chemically similar to benzoate, is the primary active metabolite of the common over the counter drug aspirin. Salicylate also resemble benzoate in its interactions with the multiple antibiotic resistance (mar) operon, upregulating the activator protein MarA. Given salicylate’s commonalities with benzoate and its long history of human use, the molecule may act selectively on our gut microbiota, increasing the proportion of genotypes in the microbiome population, such as the antibiotic susceptible benzoate evolved mutants in the lab. Mice were bred in the Neuroscience breeding facility at Kenyon College and at 8 weeks of age, a treatment group of mice(n=12) were given water dosed with sodium salicylate(25 mg/100ml), and control mice(n=12) were given additive free water. Fecal samples were collected the day before the introduction of salicylate and at 28 days from first collection. DNA was isolated from fecal samples with the MoBio Power Fecal Kit and sequenced using Illumina Hiseq (2X150bp), to obtain the fragmented genomes of all organismal DNA present. The sequence reads were aligned against a comprehensive antibiotic resistance database (CARD) using Bowtie2 software, finding notable tet, mex and cfxA family genes present. Taxonomic abundance were also obtained from sequence reads using the taxonomic classifier software Kaiju. Principle Component Analysis and DSEQ software were used to assess the effects of salicylate before and after its introduction into diet, finding salicylate associated increases in β-lactamase gene abundance and no significant changes in gut phyla.

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