Environmental Salinity Determines the Specificity and Need for Tat-Dependent Secretion of the YwbN Protein in Bacillus subtilis

Twin-arginine protein translocation (Tat) pathways are required for transport of folded proteins across bacterial, archaeal and chloroplast membranes. Recent studies indicate that Tat has evolved into a mainstream pathway for protein secretion in certain halophilic archaea, which thrive in highly saline environments. Here, we investigated the effects of environmental salinity on Tat-dependent protein secretion by the Gram-positive soil bacterium Bacillus subtilis, which encounters widely differing salt concentrations in its natural habitats. The results show that environmental salinity determines the specificity and need for Tat-dependent secretion of the Dyp-type peroxidase YwbN in B. subtilis. Under high salinity growth conditions, at least three Tat translocase subunits, namely TatAd, TatAy and TatCy, are involved in the secretion of YwbN. Yet, a significant level of Tat-independent YwbN secretion is also observed under these conditions. When B. subtilis is grown in medium with 1% NaCl or without NaCl, the secretion of YwbN depends strictly on the previously described “minimal Tat translocase” consisting of the TatAy and TatCy subunits. Notably, in medium without NaCl, both tatAyCy and ywbN mutants display significantly reduced exponential growth rates and severe cell lysis. This is due to a critical role of secreted YwbN in the acquisition of iron under these conditions. Taken together, our findings show that environmental conditions, such as salinity, can determine the specificity and need for the secretion of a bacterial Tat substrate

CT angiography; useful in non-selected outpatients?

Dance has been a part of the physical education (PE) curriculum in several countries for a longtime. In spite of this, studies demonstrate that the position of dance in the subject of PE iscontested and that little time is devoted to dance. The overall aim of this article is to examine theposition of dance as a pedagogical discourse in Swedish steering documents over time. Theempirical material consists of five Swedish curricula for PE over a period of 50 years (1962–2011).Discourse analysis is used to identify organised systems of meaning, including privileged andprioritised values. Our theoretical frame of reference draws on Bernstein’s concept of codes. Threedifferent knowledge areas within dance are found in the text material: ‘dance as cultural preserver’,‘dance as bodily exercise’ and ‘dance as expression’. Three pedagogical discourses emerge fromthese knowledge areas: an identity formation discourse, a public health discourse and an aestheticdiscourse. The identity formation discourse in earlier curricula focuses on the perpetuation ofSwedish and Nordic cultural traditions, while in later curricula, it emphasises the construction of abroader multicultural identity formation related to the understanding of different cultures. Thepublic health discourse constitutes a prioritised understanding of dance as physical training relatedto a healthy lifestyle. The aesthetic discourse, which has the weakest position over time, representsthe valuing of embodied experiences and feelings expressed through movements. This discourse isclosely linked to the construction of gender. Over time, a new performance code came to surpassthe former competence code in the steering documents. The performance code positions dance inPE as mainly a physical activity with little artistic or aesthetic value. The pedagogical discourse ofdance remains within a highly disciplinary framework of social control

Fingertip digital thermal monitoring: a fingerprint for cardiovascular disease?

Cardiac Dysfunction and Arrhythmia

100 kV versus 120 kV: effective reduction in radiation dose?

Atherosclerosi

Use of the anterior-posterior chest diameter in CT: reduction in radiation dose?

Vascular Biology and Interventio

Increased accuracy in computed tomography coronary angiography; a new body surface area adapted protocol

Vascular Biology and Interventio

Cardiac resynchronization therapy; the importance of evaluating cardiac metabolism

Cardiac Dysfunction and Arrhythmia

The Twin-Arginine Translocation Pathway in α-Proteobacteria Is Functionally Preserved Irrespective of Genomic and Regulatory Divergence

The twin-arginine translocation (Tat) pathway exports fully folded proteins out of the cytoplasm of Gram-negative and Gram-positive bacteria. Although much progress has been made in unraveling the molecular mechanism and biochemical characterization of the Tat system, little is known concerning its functionality and biological role to confer adaptive skills, symbiosis or pathogenesis in the α-proteobacteria class. A comparative genomic analysis in the α-proteobacteria class confirmed the presence of tatA, tatB, and tatC genes in almost all genomes, but significant variations in gene synteny and rearrangements were found in the order Rickettsiales with respect to the typically described operon organization. Transcription of tat genes was confirmed for Anaplasma marginale str. St. Maries and Brucella abortus 2308, two α-proteobacteria with full and partial intracellular lifestyles, respectively. The tat genes of A. marginale are scattered throughout the genome, in contrast to the more generalized operon organization. Particularly, tatA showed an approximately 20-fold increase in mRNA levels relative to tatB and tatC. We showed Tat functionality in B. abortus 2308 for the first time, and confirmed conservation of functionality in A. marginale. We present the first experimental description of the Tat system in the Anaplasmataceae and Brucellaceae families. In particular, in A. marginale Tat functionality is conserved despite operon splitting as a consequence of genome rearrangements. Further studies will be required to understand how the proper stoichiometry of the Tat protein complex and its biological role are achieved. In addition, the predicted substrates might be the evidence of role of the Tat translocation system in the transition process from a free-living to a parasitic lifestyle in these α-proteobacteria