The measurement of collaborative culture in secondary schools: An informal subgroup approach

Research on teacher collaboration underlines the importance of a collaborative culture for teachers’ functioning. However, while scholars usually regard collaborative culture as a school team characteristic, this study argues that subgroups may be more meaningful units of analysis to conceptualize and assess teachers’ perceptions of collaborative culture. Based on the assumption that collaborative culture is developed, expressed, and maintained in frequent work-related interactions, this study hypothesizes that collaborative culture is not homogenously spread over the school but rather varies between informal subgroups. Data from 760 Flemish teachers were examined using social network analysis and consensus analyses. The results provided evidence that perceptions on collaborative culture are more homogeneous within informal subgroups that are characterized by frequent interactions than the entire school team. This finding stresses the importance of assessing the meaningful unit of analysis for collective-level and socially-constructed concepts, such as collaborative culture. Moreover, the benefits and potential of a social network approach to identify (socially stable) subunits within the school team are illustrated

A Polarised Population of Dynamic Microtubules Mediates Homeostatic Length Control in Animal Cells

An analysis of cells grown on micro-patterned lines, and of cells during zebrafish development, identifies a population of microtubules that align along the long axis of cells to mediate homeostatic length control

Assessment of Microbial Diversity in Biofilms Recovered from Endotracheal Tubes Using Culture Dependent and Independent Approaches

Ventilator-associated pneumonia (VAP) is a common nosocomial infection in mechanically ventilated patients. Biofilm formation is one of the mechanisms through which the endotracheal tube (ET) facilitates bacterial contamination of the lower airways. In the present study, we analyzed the composition of the ET biofilm flora by means of culture dependent and culture independent (16 S rRNA gene clone libraries and pyrosequencing) approaches. Overall, the microbial diversity was high and members of different phylogenetic lineages were detected (Actinobacteria, beta-Proteobacteria, Candida spp., Clostridia, epsilon-Proteobacteria, Firmicutes, Fusobacteria and gamma-Proteobacteria). Culture dependent analysis, based on the use of selective growth media and conventional microbiological tests, resulted in the identification of typical aerobic nosocomial pathogens which are known to play a role in the development of VAP, e.g. Staphylococcus aureus and Pseudomonas aeruginosa. Other opportunistic pathogens were also identified, including Staphylococcus epidermidis and Kocuria varians. In general, there was little correlation between the results obtained by sequencing 16 S rRNA gene clone libraries and by cultivation. Pyrosequencing of PCR amplified 16 S rRNA genes of four selected samples resulted in the identification of a much wider variety of bacteria. The results from the pyrosequencing analysis suggest that these four samples were dominated by members of the normal oral flora such as Prevotella spp., Peptostreptococcus spp. and lactic acid bacteria. A combination of methods is recommended to obtain a complete picture of the microbial diversity of the ET biofilm

Effects of the Tubulin-Colchicine Complex on Microtubule Dynamic Instability

Original article can be found at: http://pubs.acs.org/journals/bichaw/index.html Copyright American Chemical Society DOI: 10.1021/bi00176a007 [Full text of this article is not available in the UHRA]The effects of the tubulin-olchicine complex (Tu-Col) on the dynamic behavior of microtubules have been examined under steady-state conditions in vitro. The addition of Tu-Col to tubulin microtubules at steady state results in only partial microtubule disassembly. Nevertheless, both the rate and the extent of tubulin exchange into microtubules are markedly suppressed by concentrations of Tu-Col which are low relative to the total amount of free tubulin. In addition, the time-dependent changes in microtubule length distribution, characteristic of dynamic instability, are suppressed by the addition of Tu-Col. Examination by video-enhanced dark-field microscopy of individual microtubules in the presence of Tu-Col shows that the principal effect of this complex is to reduce the growth rate at both ends of the microtubule. We have used computer simulation to rationalize the action of Tu-Col in terms of its effects on the experimentally observable parameters, namely, the rates of growth and shortening and the mean lifetimes of growth and shortening, which provide an empirical description of the dynamic behavior of microtubules. The results have been interpreted within the framework of the lateral cap formulation for microtubule dynamic instability [Martin, S. R., Schilstra, M. J., & Bayley, P. M. (1993) Biophys. J. 65, 578-5961, The simplest model mechanism requires only that Tu-Col binds to the microtubule end and inhibits further addition reactions in either the 5-start or the %start direction of the microtubule lattice. Monte Carlo simulations show that Tu-Col can, in this way, cause major suppression of the dynamic transitions of microtubules without inducing bulk microtubule disassembly. This type of mechanism could be important for the regulation of microtubule dynamics in vivo.Peer reviewe

Phaeobacter caeruleus sp nov., a blue-coloured, colony-forming bacterium isolated from a marine electroactive biofilm

Three isolates (LMG 24369(T), LMG 24370 and R-26156) obtained from a marine electroactive biofilm that was grown on a cathodically polarized electrode were investigated by using a polyphasic taxonomic approach. Whole-cell fatty acid methyl ester and 16S rRNA gene sequence analyses indicated that the isolates were members of the genus Phaeobacter, class Alphaproteobacteria. Genotypic and phenotypic analyses demonstrated that the three isolates represent a novel species of the genus Phaeobacter, for which the name Phaeobacter caeruleus sp. nov. is proposed. The type strain is LMG 24369(T) (=CCUG 55859(T)). The DNA G + C content of strain LMG 24369(T) is 63.6 mol%