Expression of VjbR under Nutrient Limitation Conditions Is Regulated at the Post-Transcriptional Level by Specific Acidic pH Values and Urocanic Acid

VjbR is a LuxR homolog that regulates transcription of many genes including important virulence determinants of the facultative intracellular pathogen Brucella abortus. This transcription factor belongs to a family of regulators that participate in a cell-cell communication process called quorum sensing, which enables bacteria to respond to changes in cell population density by monitoring concentration of self produced autoinducer molecules. Unlike almost all other LuxR-type proteins, VjbR binds to DNA and activates transcription in the absence of any autoinducer signal. To investigate the mechanisms by which Brucella induces VjbR-mediated transcriptional activation, and to determine how inappropriate spatio-temporal expression of the VjbR target genes is prevented, we focused on the study of expression of vjbR itself. By assaying different parameters related to the intracellular lifestyle of Brucella, we identified a restricted set of conditions that triggers VjbR protein expression. Such conditions required the convergence of two signals of different nature: a specific pH value of 5.5 and the presence of urocanic acid, a metabolite involved in the connection between virulence and metabolism of Brucella. In addition, we also observed an urocanic acid, pH-dependent expression of RibH2 and VirB7, two additional intracellular survival-related proteins of Brucella. Analysis of promoter activities and determination of mRNA levels demonstrated that the urocanic acid-dependent mechanisms that induced expression of VjbR, RibH2, and VirB7 act at the post-transcriptional level. Taken together, our findings support a model whereby Brucella induces VjbR-mediated transcription by modulating expression of VjbR in response to specific signals related to the changing environment encountered within the host

On the Relation Between Teachers’(In) formal Learning and Innovative Working Behavior: the Mediating Role of Employability.

Teachers’ innovative work behavior and professional development is receiving more attention lately. More precisely, it is argued that teachers’ formal and informal learning is crucial to anticipate and deal with continuous changes and innovations in technology and didactics, for example. Therefore, this study researches the teachers’ innovative work behavior by studying relations between (in)formal learning activities, employability (i.e. five competences: occupational expertise, anticipation and optimization, personal flexibility, corporate sense and balance) and innovative working behavior (IWB, i.e. ideas generation, promotion and realization). Furthermore, the mediating role of employability between learning and innovative working behavior is studied, too. Based on path analysis conducted on questionnaire data from 301 primary and secondary school teachers from the French-speaking community of Belgium, findings conclude that employability competences are related to both formal and informal learning, but the relationship between informal learning and employability is stronger. Next, making a distinction between the frequency and use of social informal learning is relevant given the differentiated role the different components play. Feedback use in particular seems to play an important role in teachers’ employability and IWB. Finally, it can be concluded that employability partially mediates the relation between the undertaking of (in)formal learning activities and dimensions of innovative working behavior. Results imply that schools should pay more attention to supporting teachers’ informal learning since it’s crucial for improving their ability to innovate and to be able to deal with changes in the dynamic world of education