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Course-based undergraduate research experiences (CUREs) integrate authentic research into undergraduate chemistry laboratories, introducing students to research while simultaneously reinforcing fundamental concepts. Despite their ubiquitous nature in bioanalytical research, few CUREs have been published applying the fundamental techniques of separations, spectroscopy, quantification, and mass spectrometry. To engage students in learning these increasingly essential bioanalytical techniques, we designed and implemented a semester-long project-based course centered around the purification, quantification, and identification of heterologously expressed proteins in five succinct and adaptable modules. Instructors can use these modules to form the foundation of a CURE specific to their research interests. The extensive commercial availability of plasmids for transformation combined with the modular approach to laboratory experiments enables convenient customization to accommodate diverse research goals. Instructors can tailor the modules to meet the curricular requirements and instrumentation capabilities of their institutions and can easily extend the research goals to incorporate more specialized analytical techniques, as needed. Through the implementation of the five modules, students apply the fundaments of acid-base chemistry, statistics, quantification strategies, spectrophotometry, separations, and mass spectrometry, thus covering the material required in most undergraduate introductory analytical courses. Instructors can then use these modules as a backbone to support student-led discovery-based investigations for the remainder of the course. Students demonstrate their understanding through the completion of a comprehensive, publication-style laboratory report as well as a poster presentation at a university-wide undergraduate research symposium. Since first offering this course in 2016, student evaluations have been exceedingly positive, with over 75% of students indicating that the course both increased their scientific skills as well as their confidence in their ability to succeed in further science courses. Furthermore, 22% of students reported they were "much more" or "extremely more" likely to enroll in a Ph.D. program in science, math, or engineering following the courses, emphasizing the impact that project-based laboratories can have on undergraduate chemists' career trajectories.

Cyanothece sp. ATCC 51142 is an aerobic [N.sub.2]-fixing and hydrogen-producing cyanobacterium. Isotopomer analysis of its amino acids revealed an identical labelling profile for leucine and isoleucine when Cyanothece 51142 was grown mixotrophically using 2-[sup.13]C-labelled glycerol as the main carbon source. This indicated that Cyanothece 51142 employs the atypical alternative citramalate pathway for isoleucine synthesis, with pyruvate and acetyI-CoA as precursors. Utilization of the citramalate pathway was confirmed by an enzyme assay and LC-MS/MS analysis. Furthermore, the genome sequence of Cyanothece 51142 shows that the gene encoding the key enzyme (threonine ammonia-lyase) in the normal isoleucine pathway is missing. Instead, the cce_0248 gene in Cyanothece 51142 exhibits 53 % identity to the gene encoding citramalate synthase (CimA, GSU1798)from Geobacter sulfurreducens. Reverse-transcription PCR indicated that the cce_0248 gene is expressed and its transcriptional level is lower in medium with isoleucine than in isoleucine-free medium. Additionally, a BLAST search for citramalate synthase and threonine ammonia-lyase implies that this alternative isoleucine synthesis pathway may be present in other cyanobacteria, such as Cyanothece and Synechococcus. This suggests that the pathway is more widespread than originally thought, as previous identifications of the citramalate pathway are limited to mostly anaerobic bacteria or archaea. Furthermore, this discovery opens the possibility that such autrotrophic micro-organisms may be engineered for robust butanol and propanol production from 2-ketobutyrate, which is an intermediate in the isoleucine biosynthesis pathway. DOI 10.1099/mic.0.031799-0