Determination of Real-Time Efflux Phenotypes in Escherichia coli AcrB Binding Pocket Phenylalanine Mutants Using a 1,2′-Dinaphthylamine Efflux Assay

To evaluate the importance of phenylalanine residues for substrate transport in the Escherichia coli efflux pump protein AcrB, we subjected Phe-to-Ala binding pocket mutants to a real-time efflux assay with the novel near-infrared lipophilic membrane probe 1,2′-dinaphthylamine (1,2′-DNA). All mutations, with the exception of F617A, led to considerable retardation of efflux. F610A was the point mutation with the most pronounced impact, followed by F628A, F615A, F136A, and F178A. This is the first study to demonstrate the importance of single phenylalanine residues within the AcrB binding pocket for real-time substrate transport

Antibiotic Stress, Genetic Response and Altered Permeability of E. coli

BACKGROUND: Membrane permeability is the first step involved in resistance of bacteria to an antibiotic. The number and activity of efflux pumps and outer membrane proteins that constitute porins play major roles in the definition of intrinsic resistance in Gram-negative bacteria that is altered under antibiotic exposure. METHODOLOGY/PRINCIPAL FINDINGS: Here we describe the genetic regulation of porins and efflux pumps of Escherichia coli during prolonged exposure to increasing concentrations of tetracycline and demonstrate, with the aid of quantitative real-time reverse transcriptase-polymerase chain reaction methodology and western blot detection, the sequence order of genetic expression of regulatory genes, their relationship to each other, and the ensuing increased activity of genes that code for transporter proteins of efflux pumps and down-regulation of porin expression. CONCLUSIONS/SIGNIFICANCE: This study demonstrates that, in addition to the transcriptional regulation of genes coding for membrane proteins, the post-translational regulation of proteins involved in the permeability of Gram-negative bacteria also plays a major role in the physiological adaptation to antibiotic exposure. A model is presented that summarizes events during the physiological adaptation of E. coli to tetracycline exposure

Reservists and veterans: Viewed from within and without

This chapter describes two important groups relative to military service – reservists and veterans. Definitions are provided regarding who is a member of each group. A summary of past and current research findings for each group is provided. The summary is organized by investigative topics or themes, which provide the current scope of the field for reservists and for veterans. Finally, approaches to the study of reservists and veterans are described, along with challenges – both substantively and methodologically – for future research studies. These serve as fertile areas for improvements and investigations in future research studies

The Perils and Promises of Self-Disclosure on Social Media

In addition to their professional social media accounts, individuals are increasingly using their personal profiles and casual posts to communicate their identities to work colleagues. They do this in order to ‘stand out from the crowd’ and to signal attributes that are difficult to showcase explicitly in a work setting. Existing studies have tended to treat personal posts viewed in a professional context as a problem, since they can threaten impression management efforts. These accounts focus on the attempts of individuals to separate their life domains on social media. In contrast, we present the narratives of professional IT workers in India who intentionally disrupt the boundaries between personal and professional profiles in order to get noticed by their employers. Drawing on the dramaturgical vocabulary of Goffman (1959) we shed light on how individuals cope with increased levels of self-disclosure on social media. We argue that their self-presentations can be likened to post-modern performances in which the traditional boundaries between actor and audience are intentionally unsettled. These casual posts communicate additional personal traits that are not otherwise included in professional presentations. Since there are no strict boundaries between formal front-stage and relaxed back-stage regions in these types of performance, a liminal mental state is often used, which enables a better assessment of the type of information to present on social media

Reservists and Veterans: Viewed from Within and Without

This is the final version. Available from Springer via the DOI in this record. This chapter describes two important groups relative to military service – reservists and veterans. Definitions are provided regarding who is a member of each group. A summary of past and current research findings for each group is provided. The summary is organized by investigative topics or themes, which provide the current scope of the field for reservists and for veterans. Finally, approaches to the study of reservists and veterans are described, along with challenges – both substantively and methodologically – for future research studies. These serve as fertile areas for improvements and investigations in future research studies