The porin and the permeating antibiotic: A selective diffusion barrier in gram-negative bacteria

Gram-negative bacteria are responsible for a large proportion of antibiotic resistant bacterial diseases. These bacteria have a complex cell envelope that comprises an outer membrane and an inner membrane that delimit the periplasm. The outer membrane contains various protein channels, called porins, which are involved in the influx of various compounds, including several classes of antibiotics. Bacterial adaptation to reduce influx through porins is an increasing problem worldwide that contributes, together with efflux systems, to the emergence and dissemination of antibiotic resistance. An exciting challenge is to decipher the genetic and molecular basis of membrane impermeability as a bacterial resistance mechanism. This Review outlines the bacterial response towards antibiotic stress on altered membrane permeability and discusses recent advances in molecular approaches that are improving our knowledge of the physico-chemical parameters that govern the translocation of antibiotics through porin channel

“She might have what I have got”: the potential utility of vignettes as an indirect measure of awareness in early-stage dementia

Objectives: In early-stage dementia, awareness at the meta-representational level involving a person’s appraisal of his/her own condition and its implications has usually been assessed by interview, but contextual factors may influence responding. We examined the utility of an indirect, vignette-based method of eliciting awareness. Method: Three vignettes describing early-stage dementia, established dementia and healthy ageing were used to elicit views of the problem and the kinds of advice that might be helpful for the characters depicted. Responses were obtained from 91 people with early-stage Alzheimer’s, vascular or mixed dementia, 87 carers, and 80 older controls. For the participants with dementia, awareness was assessed in separate in-depth interviews and rated on a 5-point scale for comparison purposes. Results: Participants with dementia were often able to correctly identify the problems described in the vignettes, although scoring lower than carers or controls. Participants with dementia were also able to offer advice for those depicted, although to a lesser extent than carers or controls. Ability to offer advice was greater where MMSE scores were higher. For participants with dementia, vignette scores were moderately correlated with ratings derived from interviews, and those showing limited or no awareness offered fewer items of advice than those showing some or good awareness. In addition, 29% of participants with dementia spontaneously pointed out similarities between their own condition and that of the person depicted. Conclusions: The vignette method may be useful where resources preclude the use of in-depth interviews, and may supplement in-depth interviews as part of a multi-dimensional assessment of awareness

Controversial Before Entering My Classroom: Exploring Pre-Service Teacher Experiences with Evolution Teaching and Learning in the Southeastern United States

Evolution continues to be a polarizing topic amongst the public as well as in K-12 and post-secondary classrooms. One issue that contributes to the polarization is the absence of accurate and meaningful instruction on evolution. The divide is especially pronounced in regions such as “The South”—Alabama, Georgia, Arkansas, Louisiana, Mississippi, South Carolina, North Carolina, and Tennessee—where cultural underpinnings strongly align against scientific topics dealing with human origins and change. Research shows that acceptance or rejection of evolution provides a reference for teachers’ choice whether to teach controversial topics such as evolution as well as the depth, breadth and duration of instruction. In this chapter we take a deeper look at the lived experiences of pre-service science teachers at a teaching college in the Southeastern United States in an effort to frame a context within the region by which later choices regarding teaching are made. Furthermore, we provide suggestions for improvements to teaching and learning that have implications beyond this critical region. Although public controversy surrounding evolution is widely regarded as being defining of the United States, the implications of studies here have translational value to teaching and learning evolution around the world

Using Multiple Lenses to Examine the Development of Beginning Biology Teachers’ Pedagogical Content Knowledge for Teaching Natural Selection Simulations

Pedagogical content knowledge (PCK) has become a useful construct to examine science teacher learning. Yet, researchers conceptualize PCK development in different ways. The purpose of this longitudinal study was to use three analytic lenses to understand the development of three beginning biology teachers’ PCK for teaching natural selection simulations. We observed three early-career biology teachers as they taught natural selection in their respective school contexts over two consecutive years. Data consisted of six interviews with each participant. Using the PCK model developed by Magnusson et al. (1999), we examined topic-specific PCK development utilizing three different lenses: (1) expansion of knowledge within an individual knowledge base, (2) integration of knowledge across knowledge bases, and (3) knowledge that explicitly addressed core concepts of natural selection. We found commonalities across the participants, yet each lens was also useful to understand the influence of different factors (e.g., orientation, subject matter preparation, and the idiosyncratic nature of teacher knowledge) on PCK development. This multi-angle approach provides implications for considering the quality of beginning science teachers’ knowledge and future research on PCK development. We conclude with an argument that explicitly communicating lenses used to understand PCK development will help the research community compare analytic approaches and better understand the nature of science teacher learning