Stressing Escherichia coli to educate students about research: A CURE to investigate multiple levels of gene regulation

An Oral Fluorouracil Prodrug, Capecitabine, Mitigates a Gram-Positive Systemic Infection in Mice

New classes of antibiotics are needed to fight bacterial infections, and repurposing existing drugs as antibiotics may enable rapid deployment of new treatments. Screens for antibacterials have been traditionally performed in standard laboratory media, but bacterial pathogens experience very different environmental conditions during infection, including nutrient limitation. To introduce the next generation of researchers to modern drug discovery methods, we developed a course-based undergraduate research experience (CURE) in which undergraduate students screened a library of FDA-approved drugs for their ability, in a nutrient-poor medium, to prevent the growth of the human Gram-negative bacterial pathogen Salmonella enterica serovar Typhimurium. The nine drugs identified all disrupt DNA metabolism in bacteria and eukaryotes. One of the hit compounds, capecitabine, is a well-tolerated oncology drug that is administered orally, a preferred treatment route. We demonstrated that capecitabine is more effective at inhibiting S. Typhimurium growth in nutrient-limited than in standard rich microbiological broth, an explanation for why the antibiotic activity of this compound has not been previously recognized. Capecitabine is enzymatically converted to the active pyrimidine analogue, fluorouracil (5-FU), and Gram-positive bacteria, including Staphylococcus aureus, are significantly more sensitive to 5-FU than Gram-negative bacteria. We therefore tested capecitabine for efficacy in a murine model of S. aureus peritonitis. Oral capecitabine administration reduced the colonization of tissues and increased animal survival in a dose-responsive manner. Since capecitabine is inexpensive, orally available, and relatively safe, it may have utility for treatment of intractable Gram-positive bacterial infections. IMPORTANCE As bacterial infections become increasingly insensitive to antibiotics, whether established, off-patent drugs could treat infections becomes an important question. At the same time, basic research has revealed that during infection, mammals starve pathogens for nutrients and, in response, bacteria dramatically alter their biology. Therefore, it may be fruitful to search for drugs that could be repurposed as antibiotics using bacteria grown with limited nutrients. This approach, executed with undergraduate student researchers, identified nine drugs known to interfere with the production and/or function of DNA. We further explored one of these drugs, capecitabine, a well-tolerated human oncology drug. Oral administration of capecitabine reduced infection with the human pathogen Staphylococcus aureus and increased survival in mice. These data suggest that capecitabine has potential as a therapy for patients with otherwise untreatable bacterial infections.

Student design and characterization of visible DHFR fusions for biochemistry tools to improve learning during lab exercises

Student feedback from an undergraduate biochemistry lab course suggested the use of visibly traceable proteins may assist learning. Based on this feedback, we used guided inquiry lab exercises where students developed and characterized a suite of fluorescent protein-dihydrofolate reductase (DHFR) fusions as tools for a biochemistry teaching lab. In contrast to the unfused versions, members of this suite are well-expressed, soluble, visible, highly stable, and easily characterized. The color of mCherry and EGFP fluorescent fusions with microbial DHFR allows students to visibly track their target protein from expression through purification under ambient light, while fusions with BFP are visible under UV-light. Fusions were made to both wild-type and kinetically enhanced DHFR variants. Importantly, we found that fluorescent protein fusions with DHFR did not kinetically interfere as the K_M and k_cat values were not remarkably altered from the unfused variant. With these fusions, students can easily measure kinetic parameters under steady-state conditions with readily available substrate and common laboratory spectrophotometers. Additionally, students also determined IC50 values of trimethoprim for DHFR. These exercises can be completed in a series of up to six lab periods and we have included the protocols for instructors who wish undertake a similar series of experiments in their biochemistry teaching labs. Using these visible fusion enzymes with subsequent students, we observed potential learning gains on a course assessment and received positive student feedback. We suggest that the often over-looked element of visual cues in a biochemistry lab may be an exploitable component of learning.

Fear of the CURE: A Beginner's Guide to Overcoming Barriers in Creating a Course-Based Undergraduate Research Experience

Over the past decade, growing evidence has shown that there are many benefits to undergraduate students engaging in scientific research, including increased persistence in pursuing STEM careers and successful outcomes in graduate study. With these benefits in mind, there has been a significant push toward providing research opportunities for students in STEM majors. To address this need, an increasing number of undergraduate courses have been developed to provide students with research experiences in a class setting, also known as course-based undergraduate research experiences, or CUREs. Despite the growing success of these courses, a number of barriers remain that deter faculty from developing and implementing CUREs. Here, we will review the perceived challenges of developing a CURE and provide practical strategies to overcome these challenges.

Anticipated learning outcomes for a biochemistry course-based undergraduate research experience aimed at predicting protein function from structure: Implications for assessment design

Several course-based undergraduate research experiences (CUREs) have been published in the literature. However, only limited attempts have been made to rigorously identify the discovery-type research abilities that students actually develop during such experiences. Instead, there has been a greater focus on technical or procedural-type knowledge or general CURE skills that are too comprehensive to effectively assess. Before the extent of discovery-type learning outcomes can be established in students (termed verified learning outcomes or VLOs), it is important to rigorously identify the anticipated learning outcomes (ALOs) and to then develop student assessments that target each ALO to reveal the nature of such student learning. In this article we present a matrix of 43 ALOs, or course-based undergraduate research abilities (CURAs), that instructors anticipate students will develop during a recently-developed biochemistry CURE focusing on the prediction of protein function from structure. The CURAs were identified using the process for identifying course-based undergraduate research abilities (PICURA) and classified into seven distinct themes that enabled the characterization of the CURE and a comparison to other published inventories of research competencies and CURE aspects. These themes and the CURE protocols aligning to the CURAs were used to form the ALO matrix that was, in turn, used to inform the design of an assessment that revealed evidence that a student had developed some of the targeted CURAs. Future research will focus on further assessment development that targets other identified CURAs. This approach has potential applications to other CUREs both in biochemistry and other science disciplines. © 2018 International Union of Biochemistry and Molecular Biology, 46(5):478-492, 2018.