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SUMMARY Bacterial cell wall synthesis is the target for some of our most powerful antibiotics and has thus been the subject of intense research focus for more than 50 years. Surprisingly, we still lack a fundamental understanding of how bacteria build, maintain and expand their cell wall. Due to technical limitations, directly testing hypotheses about the coordination and biochemistry of cell wall synthesis enzymes or architecture has been challenging, and interpretation of data has therefore often relied on circumstantial evidence and implicit assumptions. A number of recent papers have exploited new technologies, like single molecule tracking and real-time, high resolution temporal mapping of cell wall synthesis processes, to address fundamental questions of bacterial cell wall biogenesis. The results have challenged established dogmas and it is therefore timely to integrate new data and old observations into a new model of cell wall biogenesis in rod-shaped bacteria.

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2015): Evaluating listening and speaking skills in a mobile game-based learning environment with situational contexts, Computer Assisted Language Learning, Game-based learning activities that facilitate students' listening and speaking skills were designed in this study. To participate in learning activities, students in the control group used traditional methods, while students in the experimental group used a mobile system. In our study, we looked into the feasibility of mobile game-based learning activities. One experiment was carried out and the results revealed that the experimental-group students significantly outperformed the control-group students on the verbal post-test. However, the performance of the two groups was equal on the listening post-test. Two variables (the average score for the interactive jigsaw game and the number of designed cards) were found to be the most important factors for influencing students' performance in the verbal post-test. Furthermore, most students had positive perceptions toward learning activities that are supported by a mobile system. These results suggest that game-based learning activities can significantly improve students' speaking skills if driven by a mobile system. Furthermore, these results suggest that learning activities with a mobile system foster students to (1) practice speaking English as a foreign language (EFL) more frequently as well as to reflect on their speech; (2) create meaningful sentences and speak with greater accuracy and confidence; and (3) practice speaking EFL in an authentic context.

Bacteria surround themselves with peptidoglycan, an adaptable enclosure that contributes to cell shape and stability. Peptidoglycan assembly relies on penicillin-binding proteins (PBPs) acting in concert with SEDS-family transglycosylases RodA and FtsW, which support cell elongation and division respectively. In Bacillus subtilis, cells lacking all four PBPs with transglycosylase activity (aPBPs) are viable. Here, we show that the alternative sigma factor σI is essential in the absence of aPBPs. Defects in aPBP-dependent wall synthesis are compensated by σI-dependent upregulation of an MreB homolog, MreBH, which localizes the LytE autolysin to the RodA-containing elongasome complex. Suppressor analysis reveals that cells unable to activate this σI stress response acquire gain-of-function mutations in the essential histidine kinase WalK, which also elevates expression of sigI, mreBH and lytE. These results reveal compensatory mechanisms that balance the directional peptidoglycan synthesis arising from the elongasome complex with the more diffusive action of aPBPs.