May 5, 2017
Antibiotic Resistance Genes in Minnesota Soil Bacteria from Areas of High and Low Ferric Iron
Gunner Drossel '17Naturally-occurring antibiotic resistance genes in soil bacteria represent a potentially important reservoir of genes that could contribute to antibiotic resistance of human pathogens. It has been reported that over 40 genes in bacterial genomes are controlled by concentrations of ferric iron. We examined the effect of soil metal content on the level of resistance to two antibiotics, ampicillin (Amp) and tetracycline (Tet), and the presence of multiple genes that code for efflux pump-mediated resistance. These pumps act to export toxins (e.g. heavy metals and antibiotics, perhaps). Because of this, growth in heavy metal-contaminated soils might select for antibiotic resistance. Ninety-six soil samples were collected over the course of two summers from areas of Minnesota with known high and low ferric iron, as reported by the US Dept. of Interior. Samples were plated on LB plates with either 10 mg/500mL Tet or 50 mg/500mL Amp. Tet resistance was the same in high and low iron soils (p = 0.63, sd = 0.02). Amp resistance was higher in samples from high iron soils only in 2015’s data (2015 p =0.002; 2016 p = 0.75, sd = 38.1). Distribution of resistance was, however, significant for Tet between iron concentrations (p < 0.001). Additionally, total DNA was extracted and PCRs with gel electrophoresis was used to determine the prevalence of 14 different efflux genes (acrB,D,F; emrB,E; mdfA; tehA; yhiV; mexF,Y; tetC,H,B,D) common to soil bacteria. In 2015, five of the eight genes studied were seen in high iron soil, while only one gene was detected in low iron soil. In 2016, four of six genes were found in samples from both soils. Ferric iron levels in the soils tested were not significantly correlated with Tet or Amp resistance levels in soil bacteria in 2016, but were correlated in 2015’s data (Amp only). It is possible that other heavy metals play a more important role in selecting for antibiotic resistance than iron.
The identification of a key mutation in arrhythmogenic right ventricular cardiomyopathy (ARVC) and the resulting implications on desmosomal plakoglobin structure
Cody Jahrig '17Desmosomal proteins provide cell-to- cell adhesion through intricate complexes essential to withstanding mechanical stress in varying human epithelial and muscle tissues. When mutations are present they can be implicated in specific diseases such as arrhythmogenic right ventricular cardiomyopathy (ARVC) and Naxos disease effecting cardiomyocyte and skin cell adhesion. The goal of research surrounding these deadly mutations has sought to elucidate specific genetic alterations responsible for the phenotypic traits of both Naxos and ARVC suspected to be found within the gene encoding plakoglobin, a member of the desmosome protein complex. Until the year 2000 there had not been an identified gene associated with hereditary ARVC. To determine such mutations reverse transcriptase PCR was used to pinpoint a specific deletion in plakoglobin proteins within a sample of patients with Naxos disease. Furthermore, a method for identifying individuals with the implicated mutation was devised using restriction enzyme analysis. This research set a precedent for the elucidation of many groundbreaking discoveries in mutations prevalent to ARVC. With the use of more modern techniques like X-ray crystallography, 3D modeling can be used to visualize the structural changes to plakoglobin, and how these mutations may affect protein function, structure and intermolecular interactions. Research considering the mechanisms and pathophysiology of these plakoglobin mutations and their impact on ARVC are ongoing, and seek to elaborate on previous identifications of such mutations.
