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The emergence of big data in educational contexts has led to new data-driven approaches to support informed decision making and efforts to improve educational effectiveness. Digital traces of student behavior promise more scalable and finer-grained understanding and support of learning processes, which were previously too costly to obtain with traditional data sources and methodologies. This synthetic review describes the affordances and applications of microlevel (e.g., clickstream data), mesolevel (e.g., text data), and macrolevel (e.g., institutional data) big data. For instance, clickstream data are often used to operationalize and understand knowledge, cognitive strategies, and behavioral processes in order to personalize and enhance instruction and learning. Corpora of student writing are often analyzed with natural language processing techniques to relate linguistic features to cognitive, social, behavioral, and affective processes. Institutional data are often used to improve student and administrational decision making through course guidance systems and early-warning systems. Furthermore, this chapter outlines current challenges of accessing, analyzing, and using big data. Such challenges include balancing data privacy and protection with data sharing and research, training researchers in educational data science methodologies, and navigating the tensions between explanation and prediction. We argue that addressing these challenges is worthwhile given the potential benefits of mining big data in education.

The bacterial septum-located DNA translocase FtsK coordinates circular chromosome segregation with cell division. Rapid translocation of DNA by FtsK is directed by 8-base-pair DNA motifs (KOPS), so that newly replicated termini are brought together at the developing septum, thereby facilitating completion of chromosome segregation. Translocase functions reside in three domains, α, β and γ. FtsKαβ are necessary and sufficient for ATP hydrolysis-dependent DNA translocation, which is modulated by FtsKγ through its interaction with KOPS. By solving the FtsKγ structure by NMR, we show that γ is a winged-helix domain. NMR chemical shift mapping localizes the DNA-binding site on the γ domain. Mutated proteins with substitutions in the FtsKγ DNA-recognition helix are impaired in DNA binding and KOPS recognition, yet remain competent in DNA translocation and XerCD-dif site-specific recombination, which facilitates the late stages of chromosome segregation.The 4.6-million-base-pair (bp) circular Escherichia coli chromosome is replicated bidirectionally from a unique origin (oriC), with replication termination occurring in a broad ter region opposite oriC (reviewed in refs. 1,2). Therefore, replication divides the chromosome into two equal arms or replichores, which locate to separate halves of the E. coli cell and behave as units of chromosome segregation 3 . Each replichore is transcribed predominantly in the same direction as replication and contains distinctive asymmetric, base composition-skewed sequences on each strand. These have been implicated in recombination, genome stability and chromosome processing 1,2,4,5 . Separation and segregation of newly replicated sister chromosomes can be compromised by catenation and chromosome dimer formation. Site-specific recombination mediated by the XerCD recombinase occurs between newly replicated sister dif sites, located in ter, and acts in sister-chromosome segregation by converting any chromosome dimers to monomers and by © 2006 Nature Publishing Group Correspondence should be addressed to D.J.S. (sherratt@bioch.ox.ac.uk).. 4 These authors contributed equally to this work. AUTHOR CONTRIBUTIONS V.S., molecular biology and manuscript preparation. M.D.A., biochemistry, NMR and manuscript preparation. C.d.B., molecular biology. R.B., molecular biology. L.K.A., project direction and manuscript preparation. S.M.F., NMR. M.B., NMR. J.L., molecular biology, structural biology, project direction and manuscript preparation. D.J.S., project conception, project direction and manuscript preparation.Supplementary information is available on the Nature Structural & Molecular Biology website. COMPETING INTERESTS STATEMENTThe authors declare that they have no competing financial interests. Fig. 1a,b), containing helices H1, H2 and H3 and the C-terminal wing. We have not assigned or constrained secondary structure in the wing; in other WHD proteins, the wing usually has very few residues in true β-sheet conformation. WHDs are a subtype of helix-turn-helix DNA-binding proteins in ...

The Escherichia coli SMC complex, MukBEF, acts in chromosome segregation. MukBEF shares the distinctive architecture of other SMC complexes, with one prominent difference; unlike other kleisins, MukF forms dimers through its N-terminal domain. We show that a 4-helix bundle adjacent to the MukF dimerisation domain interacts functionally with the MukB coiled-coiled ‘neck’ adjacent to the ATPase head. We propose that this interaction leads to an asymmetric tripartite complex, as in other SMC complexes. Since MukF dimerisation is preserved during this interaction, MukF directs the formation of dimer of dimer MukBEF complexes, observed previously in vivo. The MukF N- and C-terminal domains stimulate MukB ATPase independently and additively. We demonstrate that impairment of the MukF interaction with MukB in vivo leads to ATP hydrolysis-dependent release of MukBEF complexes from chromosomes.

Cells of the oral bacterium Streptococcus gordonii express three cytoplasmic membrane-bound lipoproteins with apparent molecular masses of 76 to 78 kDa that are the products of three genes (designated hppA, hppG, and hppH). The lipoproteins are immunologically cross-reactive, contain 60% or more identical amino acid residues, and are highly similar to the AmiA, AliA (PlpA), and AliB substrate-binding protein components of an oligopeptide permease in Streptococcus pneumoniae. Insertional inactivation of the hppA or hppH gene resulted in loss of the ability of S. gordonii cells to utilize specific peptides of five to seven amino acid residues for growth. An insertion within the COOH-terminal coding region of hppG that caused apparent truncation of the HppG polypeptide had a similar effect; however, S. gordonii mutants in which HppG polypeptide production was abolished were still able to grow on all oligopeptides tested. Inactivation of hppA gene (but not inactivation of the hppG or hppH gene) caused reduced growth rate of cells in complex medium, slowed the rate of development of competence for transformation, reduced the efficiency of transformation, and increased the resistance of cells to aminopterin. These results suggest that the formation of a solute-binding-protein complex consisting of at least the HppA and the HppH lipopolypeptides is necessary for binding and subsequent uptake of primarily hexa-or heptapeptides by a Hpp (Hexa-heptapeptide permease) system in S. gordonii. In addition, Hpp may play a role in the control of metabolic functions associated with the growth of streptococcal cells on complex nitrogen sources and with the development of competence.Binding-protein-dependent transport systems for the uptake of nutrients by bacteria are members of the ubiquitous family of ATP-binding-cassette (ABC)-type transporters (20). The binding-protein-dependent systems are responsible for the transmembrane uptake into bacteria of a wide range of substrates including saccharides, amino acids, peptides, vitamins, anions, and cations (52). The systems consist of one or two transmembrane protein components forming the solute-specific channel, one or two ATP-binding proteins associated with the cytoplasmic side of the membrane, and an extracellular ligand-specific binding protein. The last component is located in the periplasm of gram-negative bacteria, while in grampositive bacteria it is lipid modified and is associated with the external face of the cytoplasmic membrane (51).Uptake systems of this type in bacteria have a wide range of substrate specificities. Some systems have become evolved to transport specific molecules, while others transport a variety of ligands exhibiting similar chemical structures. For the uptake of peptides by bacteria, essentially three ABC-type permeases have been identified that preferentially transport dipeptides, tripeptides, or larger peptides. The dipeptide permease (Dpp) in Escherichia coli and Salmonella typhimurium is a bindingprotein-dependent transport system that transports...