Transcription activation in Escherichia coli and Salmonella

Promoter-specific activation of transcript initiation provides an important regulatory device in Escherichia coli and Salmonella. Here, we describe the different mechanisms that operate, focusing on how they have evolved to manage the "housekeeping" bacterial transcription machinery. Some mechanisms involve assisting the bacterial DNA-dependent RNA polymerase or replacing or remodeling one of its subunits. Others are directed to chromosomal DNA, improving promoter function, or relieving repression. We discuss how different activators work together at promoters and how the present complex network of transcription factors evolved

Laboratory strains of Escherichia coli K-12: things are seldom what they seem

Escherichia coli K-12 was originally isolated 100 years ago and since then it has become an invaluable model organism and a cornerstone of molecular biology research. However, despite its pedigree, since its initial isolation E. coli K-12 has been repeatedly cultured, passaged and mutagenized, resulting in an organism that carries many genetic changes. To understand more about this important model organism, we have sequenced the genomes of two ancestral K-12 strains, WG1 and EMG2, considered to be the progenitors of many key laboratory strains. Our analysis confirms that these strains still carry genetic elements such as bacteriophage lambda (λ) and the F plasmid, but also indicates that they have undergone extensive laboratory-based evolution. Thus, scrutinizing the genomes of ancestral E. coli K-12 strains leads us to examine whether E. coli K-12 is a sufficiently robust model organism for 21st century microbiology

Students’ Self-Perceptions of Self-Awareness/Self-Regulation when Experiencing Unexpected Situations in an Interprofessional Clinical Simulation

Background: The healthcare environment is becoming increasingly complex and demanding; therefore, providers need to possess both technical and non-technical skills to respond in unexpected circumstances. Self-awareness and regulation are non-technical skills where an individual becomes aware of personal and others’ emotions and then modulates those emotions to effectively act during a challenging situation. Educational programs need to embed more opportunities for students to develop these skills to enhance patient outcomes. Purpose: The purpose of this research study was to explore student self-perceptions of self-awareness and self-regulation when experiencing unexpected situations in an interprofessional clinical simulation. Methods: Healthcare students (n = 109) from four disciplines participated in this qualitative research study involving an interprofessional small group, face to face simulation with unexpected circumstances. Following the simulation, participants engaged in a semi-structured debriefing. Comments were recorded and analyzed to develop a thematic structure. Results: Participants had varying views about their level of preparedness to handle complex, unexpected situations ranging from feeling not prepared at all to recognizing that they need to be equipped for anything. Students also reported a greater appreciation for the interprofessional team, acknowledging the need for one another as they navigated unexpected circumstances. Some students used their self-awareness and regulation skills in the moment to manage their emotions and move to action in response to the unexpected circumstances, while others benefited from observing and hearing from others during the simulation and debriefing session. Conclusions: The interprofessional simulation helped to prepare students to navigate unexpected challenging patient care circumstances. Students experienced some role and action confusion in response to the emotionally charged scenario; however, they recognized the importance of being self-aware, regulating their own emotions and the skills of the interdisciplinary team to best meet the needs of the patient and family. Additional opportunities for non-technical skill practice should be included in healthcare curriculums to enhance students’ preparedness for the current healthcare environment. Further research is recommended to determine best practices for teaching these non-technical skills

New Vectors for Urea-Inducible Recombinant Protein Production

We have developed a novel urea-inducible recombinant protein production system by exploiting the Proteus mirabilis urease ureR-ureD promoter region and the ureR AraC-family transcriptional regulator. Experiments using the expression of β-galactosidase and green fluorescent protein (GFP) showed that promoter activity is tightly regulated and that varying the concentration of urea can give up to 100-fold induction. Production of proteins of biopharmaceutical interest has been demonstrated, including human growth hormone (hGH), a single chain antibody fragment (scFv) against interleukin-1β and a potential Neisserial vaccine candidate (BamAENm). Expression levels can be fine-tuned by temperature and different urea concentrations, and can be induced with readily available garden fertilisers and even urine. As urea is an inexpensive, stable inducer, a urea-induced expression system has the potential to considerably reduce the costs of large-scale recombinant protein production

Escherichia coli ‘TatExpress’ strains super-secrete human growth hormone into the bacterial periplasm by the Tat pathway

Numerous high-value proteins are secreted into the Escherichia coli periplasm by the General Secretory (Sec) pathway, but Sec-based production chassis cannot handle many potential target proteins. The Tat pathway offers a promising alternative because it transports fully folded proteins; however, yields have been too low for commercial use. To facilitate Tat export, we have engineered the TatExpress series of super-secreting strains by introducing the strong inducible bacterial promoter, ptac, upstream of the chromosomal tatABCD operon, to drive its expression in E. coli strains commonly used by industry (e.g. W3110 and BL21). This modification significantly improves the Tat-dependent secretion of human growth hormone (hGH) into the bacterial periplasm, to the extent that secreted hGH is the dominant periplasmic protein after only 1?h induction. TatExpress strains accumulate in excess of 30?mg?L?1 periplasmic recombinant hGH, even in shake flask cultures. A second target protein, an scFv, is also shown to be exported at much higher rates in TatExpress strain

Direct observation of conductive filament formation in Alq3 based organic resistive memories

This work explores resistive switching mechanisms in non-volatile organic memory devices based on tris(8-hydroxyquinolie)aluminum (Alq 3 ). Advanced characterization tools are applied to investigate metal diffusion in ITO/Alq 3 /Ag memory device stacks leading to conductive filament formation. The morphology of Alq 3 /Ag layers as a function of the metal evaporation conditions is studied by X-ray reflectivity, while depth profile analysis with X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry is applied to characterize operational memory elements displaying reliable bistable current-voltage characteristics. 3D images of the distribution of silver inside the organic layer clearly point towards the existence of conductive filaments and allow for the identification of the initial filament formation and inactivation mechanisms during switching of the device. Initial filament formation is suggested to be driven by field assisted diffusion of silver from abundant structures formed during the top electrode evaporation, whereas thermochemical effects lead to local filament inactivation. V C 2015 AIP Publishing LLC

1936: Abilene Christian College Bible Lectures - Full Text

Delivered in the auditorium of Abilene Christian College, Abilene, Texas, February 193