Open Inquiry versus Broadly Relevant Short-Term Research Experiences for Non-Biology Majors.

Undergraduate student participation in course-based research experiences results in many positive outcomes, but there is a lack of evidence demonstrating which elements of a research experience are necessary, especially for non-biology majors. Broad relevance is one element that can be logistically challenging to incorporate into research experiences in large-enrollment courses. We investigated the impacts of broad relevance in a short-term research experience in an introductory biology course for non-majors. Students either participated in an open-inquiry research experience (OI-RE), where they developed their own research question, or a broadly relevant research experience (BR-RE), where they investigated a question assigned to them that was relevant to an ongoing research project. We found a significant association between the type of research project experienced and students' preference for an experience, with half of the students in the OI-RE group and nearly all students in the BR-RE group preferring a broadly relevant research experience. However, since science confidence increased over the course for both groups, these findings indicate that while students who participated in a BR-RE valued it, broadly relevant research experiences may not be necessary for positive outcomes for non-majors.

Tiny Earth: A Big Idea for STEM Education and Antibiotic Discovery.

The world faces two seemingly unrelated challenges-a shortfall in the STEM workforce and increasing antibiotic resistance among bacterial pathogens. We address these two challenges with Tiny Earth, an undergraduate research course that excites students about science and creates a pipeline for antibiotic discovery.

Discovery and Broad Relevance May Be Insignificant Components of Course-Based Undergraduate Research Experiences (CUREs) for Non-Biology Majors.

Course-based undergraduate research experiences (CUREs) are a type of laboratory learning environment associated with a science course, in which undergraduates participate in novel research. According to Auchincloss et al. (CBE Life Sci Educ 2104; 13:29-40), CUREs are distinct from other laboratory learning environments because they possess five core design components, and while national calls to improve STEM education have led to an increase in CURE programs nationally, less work has specifically focused on which core components are critical to achieving desired student outcomes. Here we use a backward elimination experimental design to test the importance of two CURE components for a population of non-biology majors: the experience of discovery and the production of data broadly relevant to the scientific or local community. We found nonsignificant impacts of either laboratory component on students' academic performance, science self-efficacy, sense of project ownership, and perceived value of the laboratory experience. Our results challenge the assumption that all core components of CUREs are essential to achieve positive student outcomes when applied at scale.

A Call to Develop Course-Based Undergraduate Research Experiences (CUREs) for Nonmajors Courses.

Course-based undergraduate research experiences (CUREs) for non-science majors (nonmajors) are potentially distinct from CUREs for developing scientists in their goals, learning objectives, and assessment strategies. While national calls to improve science, technology, engineering, and mathematics education have led to an increase in research revealing the positive effects of CUREs for science majors, less work has specifically examined whether nonmajors are impacted in the same way. To address this gap in our understanding, a working group focused on nonmajors CUREs was convened to discuss the following questions: 1) What are our laboratory-learning goals for nonmajors? 2) What are our research priorities to determine best practices for nonmajors CUREs? 3) How can we collaborate to define and disseminate best practices for nonmajors in CUREs? We defined three broad student outcomes of prime importance to the nonmajors CURE: improvement of scientific literacy skills, proscience attitudes, and evidence-based decision making. We evaluated the state of knowledge of best practices for nonmajors, and identified research priorities for the future. The report that follows is a summary of the conclusions and future directions from our discussion.

Frequent replenishment sustains the beneficial microbiome of Drosophila melanogaster.

UNLABELLED: We report that establishment and maintenance of the Drosophila melanogaster microbiome depend on ingestion of bacteria. Frequent transfer of flies to sterile food prevented establishment of the microbiome in newly emerged flies and reduced the predominant members, Acetobacter and Lactobacillus spp., by 10- to 1,000-fold in older flies. Flies with a normal microbiome were less susceptible than germfree flies to infection by Serratia marcescens and Pseudomonas aeruginosa. Augmentation of the normal microbiome with higher populations of Lactobacillus plantarum, a Drosophila commensal and probiotic used in humans, further protected the fly from infection. Replenishment represents an unexplored strategy by which animals can sustain a gut microbial community. Moreover, the population behavior and health benefits of L. plantarum resemble features of certain probiotic bacteria administered to humans. As such, L. plantarum in the fly gut may serve as a simple model for dissecting the population dynamics and mode of action of probiotics in animal hosts. IMPORTANCE: Previous studies have defined the composition of the Drosophila melanogaster microbiome in laboratory and wild-caught flies. Our study advances current knowledge in this field by demonstrating that Drosophila must consume bacteria to establish and maintain its microbiome. This finding suggests that the dominant Drosophila symbionts remain associated with their host because of repeated reintroduction rather than internal growth. Furthermore, our study shows that one member of the microbiome, Lactobacillus plantarum, protects the fly from intestinal pathogens. These results suggest that, although not always present, the microbiota can promote salubrious effects for the host. In sum, our work provides a previously unexplored mechanism of microbiome maintenance and an in vivo model system for investigating the mechanisms of action of probiotic bacteria.

From commensal to pathogen: translocation of Enterococcus faecalis from the midgut to the hemocoel of Manduca sexta.

UNLABELLED: A dynamic homeostasis is maintained between the host and native bacteria of the gastrointestinal tract in animals, but migration of bacteria from the gut to other organs can lead to disease or death. Enterococcus faecalis is a commensal of the gastrointestinal tract; however, Enterococcus spp. are increasingly frequent causes of nosocomial infections with a high mortality rate. We investigated the commensal-to-pathogen switch undergone by E. faecalis OG1RF in the lepidopteran model host Manduca sexta associated with its location in the host. E. faecalis persists in the harsh midgut environment of M. sexta larvae without causing apparent illness, but injection of E. faecalis directly into the larval hemocoel is followed by rapid death. Additionally, oral ingestion of E. faecalis in the presence of Bacillus thuringiensis insecticidal toxin, a pore-forming toxin that targets the midgut epithelium, induces an elevated mortality rate. We show that the loss of gut integrity due to B. thuringiensis toxin correlates with the translocation of E. faecalis from the gastrointestinal tract into the hemolymph. Upon gaining access to the hemolymph, E. faecalis induces an innate immune response, illustrated by hemocyte aggregation, in larvae prior to death. The degree of hemocyte aggregation is dependent upon the route of E. faecalis entry. Our data demonstrate the efficacy of the M. sexta larval model system in investigating E. faecalis-induced sepsis and clarifies controversies in the field regarding the events leading to larval death following B. thuringiensis toxin exposure. IMPORTANCE: This study advances our knowledge of Enterococcus faecalis-induced sepsis following translocation from the gut and provides a model for mammalian diseases in which the spatial distribution of bacteria determines disease outcomes. We demonstrate that E. faecalis is a commensal in the gut of Manduca sexta and a pathogen in the hemocoel, resulting in a robust immune response and rapid death, a process we refer to as the "commensal-to-pathogen" switch. While controversy remains regarding Bacillus thuringiensis toxin-induced killing, our laboratory previously found that under some conditions, the midgut microbiota is essential for B. thuringiensis toxin killing of Lymantria dispar (N. A. Broderick, K. F. Raffa, and J. Handelsman, Proc. Natl. Acad. Sci. U. S. A. 103:15196-15199, 2006; B. Raymond, et al., Environ. Microbiol. 11:2556-2563, 2009; P. R. Johnston, and N. Crickmore, Appl. Environ. Microbiol. 75:5094-5099, 2009). We and others have demonstrated that the role of the midgut microbiota in B. thuringiensis toxin killing is dependent upon the lepidopteran species and formulation of B. thuringiensis toxin (N. A. Broderick, K. F. Raffa, and J. Handelsman, Proc. Natl. Acad. Sci. U. S. A. 103:15196-15199, 2006; N. A. Broderick, et al., BMC Biol. 7:11, 2009). This work reconciles much of the apparently contradictory previous data and reveals that the M. sexta-E. faecalis system provides a model for mammalian sepsis.