This report presents a summary of a meeting on assessment of course-based undergraduate research experiences (CUREs), including an operational definition of a CURE, a summary of research on CUREs, relevant findings from studies of undergraduate research internships, and recommendations for future research on and evaluation of CUREs.

MinD is a widely conserved ATPase that has been demonstrated to play a pivotal role in selection of the division site in eubacteria and chloroplasts. It is a member of the large ParA superfamily of ATPases that are characterized by a deviant Walker-type ATP-binding motif. MinD localizes to the cytoplasmic face of the inner membrane in Escherichia coli, and its association with the inner membrane is a prerequisite for membrane recruitment of the septation inhibitor MinC. However, the mechanism by which MinD associates with the membrane has proved enigmatic; it seems to lack a transmembrane domain and the amino acid sequence is devoid of hydrophobic tracts that might predispose the protein to interaction with lipids. In this study, we show that the extreme C-terminal region of MinD contains a highly conserved 8-to 12-residue sequence motif that is essential for membrane localization of the protein. We provide evidence that this motif forms an amphipathic helix that most likely mediates a direct interaction between MinD and membrane phospholipids. A model is proposed whereby the membrane-targeting motif mediates the rapid cycles of membrane attachment-release-reattachment that are presumed to occur during pole-to-pole oscillation of MinD in E. coli. D uring vegetative growth, most bacteria form a division septum at the center of the cell by coordinated ingrowth of the cytoplasmic membrane, the rigid murein (peptidoglycan) layer, and, in Gram-negative bacteria, the outer membrane of the cell envelope (1). In the rod-shaped bacterium Escherichia coli, placement of the division septum is negatively regulated by the three proteins encoded by the minB operon: MinC, MinD, and MinE (2, 3). MinC and MinD act in concert to form a global division inhibitor whose activity is restricted to polar sites by MinE (2). Studies of GFP-labeled Min proteins have revealed that they undergo a complex bipolar oscillation that causes the time-averaged concentration of the MinC-MinD division inhibitor to be lowest at midcell (4-8). This dynamic distribution of MinC-MinD makes midcell the preferred site for construction of a circumferential ring of polymerized FtsZ, which is the initiating event in bacterial cytokinesis (9).MinD is the best conserved and most widely distributed of the Min proteins, being found in all domains of life (eubacteria, archaea, and eukaryotes). It is a member of the ParA superfamily of ATPases, most of which (apart from the MinD subgroup) are involved in plasmid or chromosome partitioning (10-12). The ATPase activity of MinD is presumed to provide the driving force for pole-to-pole oscillation of the MinC-MinD division inhibitor (13,14). This activity is stimulated by MinE but only in the presence of phospholipids (13,14). MinD is a peripheral membrane protein (10), and its association with the inner membrane is a prerequisite for subsequent recruitment of both MinC and MinE to the membrane. However, the mechanism by which MinD associates with the inner membrane and subsequently recruits MinC and MinE remains enig...

Histidine kinases are used extensively in prokaryotes to monitor and respond to changes in cellular and environmental conditions. In Bacillus subtilis, sporulation-specific gene expression is controlled by a histidine kinase phosphorelay that culminates in phosphorylation of the Spo0A transcription factor. Sda provides a developmental checkpoint by inhibiting this phosphorelay in response to DNA damage and replication defects. We show that Sda acts at the first step in the relay by inhibiting autophosphorylation of the histidine kinase KinA. The structure of Sda, which we determined using NMR, comprises a helical hairpin. A cluster of conserved residues on one face of the hairpin mediates an interaction between Sda and the KinA dimerization/phosphotransfer domain. This interaction stabilizes the KinA dimer, and the two proteins form a stable heterotetramer. The data indicate that Sda forms a molecular barricade that inhibits productive interaction between the catalytic and phosphotransfer domains of KinA.

MinD is a ubiquitous ATPase that plays a crucial role in selection of the division site in eubacteria, chloroplasts, and probably also Archaea. It was recently demonstrated that membrane localization of MinD is mediated by an 8 -12-residue C-terminal motif termed the membrane targeting sequence or MTS. In this study we show that the MinD MTS is a transplantable lipid-binding motif that can effectively target heterologous proteins to the cell membrane. We demonstrate that eubacterial MTSs interact directly with lipid bilayers as an amphipathic helix, with a distinct preference for anionic phospholipids. Moreover, we provide evidence that the phospholipid preference of each MTS, as well as its affinity for biological membranes, has been evolutionarily "tuned" to its specific role in different bacteria. We propose a model to describe how the MTS is coupled to ATP binding to regulate the reversible membrane association of Escherichia coli MinD during its pole-to-pole oscillation cycle.The initiating event in bacterial cytokinesis is the formation of a circumferential ring of polymerized FtsZ, the ancestral homolog of eukaryotic tubulin (1-3). The FtsZ ring provides a scaffold onto which numerous proteins are subsequently assembled to form the functional division apparatus (4, 5). In the rod-shaped bacterium Escherichia coli, placement of the FtsZ ring, and thus the division septum, is negatively regulated by the three proteins encoded by the minB operon: MinC, MinD, and MinE (3, 6, 7). In the absence of the Min system, FtsZ rings can form either at midcell or in the nucleoid-free regions at either of the cell poles (8). Polar divisions are nonproductive as they lead to the formation of chromosomeless minicells and multinucleate filaments.MinC and MinD associate to form an indiscriminate division inhibitor whose activity is restricted to polar sites in E. coli by the action of MinE (6). Studies of GFP 1 -labeled Min proteins from the Gram-negative bacteria E. coli and Neisseria gonorrhoeae have revealed that they undergo a remarkable pole-topole oscillation that causes the time-averaged concentration of the MinCD division inhibitor to be lowest at midcell (9 -15). This makes midcell the preferred site for construction of an FtsZ ring. In contrast, Bacillus subtilis and most other Grampositive bacteria lack the MinE protein that promotes MinCD oscillation in E. coli. Instead, in B. subtilis, the MinCD complex is anchored at the cell poles by DivIVA where it remains throughout the cell cycle until a late stage in assembly of the division apparatus when it is piloted to the nascent division site (16 -18).MinD is a peripheral membrane protein (19), and its association with the inner membrane is a prerequisite for subsequent membrane recruitment of MinC (and MinE in E. coli). MinD is a member of the ParA superfamily of ATPases that are characterized by a deviant Walker A motif (19 -22). The ATPase activity of MinD provides the driving force for oscillation of the Min proteins in E. coli; this activity is stimulated by Min...

No abstract

The authors conducted a metareview of published conceptions of “authentic” science laboratory education and used their students’ reflections to examine the authenticity of their own laboratory curriculum design. They find that preauthentication of a learning design is not necessary to deliver an authentic experience to students.

Science undergraduate courses typically cater to a mixed-learner cohort, with a diversity of motivations and skills. This diversity introduces pressure for designers of the practical laboratory curriculum. Students who are struggling with the course need a series of tasks that begin simply, and transition to more conceptually difficult material. More capable students need opportunities for conceptual extension and creative activity. In this report, we examine an approach we have used to address this problem in the context of a large introductory biochemistry undergraduate class. Rather than attempting to compromise on a single practical series for our 470 students, we devised two parallel but equivalent practical streams and offered students their choice of laboratory experience. One stream (called Laboratory Experience for Acquiring Practical Skills) was designed to allow acquisition of a range of common biochemistry and molecular biology laboratory skills. The other (called Active Learning Laboratory Undergraduate Research Experience) was designed to offer an authentic (but scaffolded) undergraduate research project. We discuss the ramifications and implications of our approach in terms of funding, staffing, and assessment while also examining student motivation, satisfaction, and skills acquisition. We present data supporting the practical and pedagogical value of laboratory exercise streaming to meet the diverse needs of students. We suggest a framework that can be used to pre-emptively identify and address problems associated with a bifurcated practical series and increase the sustainability of the approach.Keywords: Active learning, assessment of educational activities, curriculum, design development and implementation, laboratory exercises, learning and curriculum design, new course development.The practical laboratory is central to an undergraduate science education [1]. The types of learning that occur in an undergraduate laboratory can (and do) range from the simple improvement of practical skills, to the development of an abstract understanding of the nature of science. There is evidence that the learning gains achieved by students are affected by the design of the laboratory exercise [2], and this idea (in theory) is well accepted in the literature. According to the dogma, a traditional ''cookbook'' laboratory exercise, for example, is likely to produce only gains at the lower points of the cognitive scale as defined in Bloom's Revised Taxonomy [3]. In contrast, a research-driven laboratory learning experience has potential to produce students with an increased ability to think in an abstract manner, define and investigate their own research problems, and develop an understanding of what it means to ''be a scientist''.There have been widespread recommendations that undergraduate science teaching should adopt researchbased learning as standard [4]. This has led to a wave of implementation and debate around student-centered, inquiry-based, and research-based laboratory programs [5][6][7]. Contexts for ...

SummaryThe Bacillus subtilis cell-division protein DivIB is shown to be present at an Ϸ100-fold higher abundance (Ϸ5000 molecules per cell) than its Escherichia coli FtsQ homologue. B. subtilis contains much more DivIB (at least 60-fold) than is needed to maintain the normal rate of cell division at moderate temperatures (up to 37ЊC). However, a high level of DivIB is needed to achieve the normal rate of division at high temperature (47ЊC). It is proposed that membrane-bound DivIB is involved in stabilizing or promoting the assembly of the division complex (which is intrinsically temperature sensitive) in a manner that requires more of the protein at higher temperatures. The (at least) 60-fold accumulation of DivIB and FtsZ from an undetectable level, following germination and outgrowth of spores up until the stage of the first cell division, was unaffected by blocking of initiation of the first round of replication. It is concluded that there is no major synthesis of either of these 'division initiation' proteins linked to initiation, progression or completion of the first round of replication accompanying spore outgrowth.