Multiple Envelope Stress Response Pathways Are Activated in an Escherichia coli Strain with Mutations in Two Members of the DedA Membrane Protein Family

We have reported that simultaneous deletion of two Escherichia coli genes, yqjA and yghB, encoding related and conserved inner membrane proteins belonging to the DedA protein family results in a number of intriguing phenotypes, including temperature sensitivity at 42°C, altered membrane lipid composition, and cell division defects. We sought to characterize these and other phenotypes in an effort to establish a function for this protein family in E. coli. Here, using reporter assays, we show that the major envelope stress response pathways Cpx, Psp, Bae, and Rcs are activated in strain BC202 (W3110; ΔyqjA ΔyghB) at the permissive growth temperature of 30°C. We previously demonstrated that 10 mM Mg(2+), 400 mM NaCl, and overexpression of tatABC are capable of restoring normal growth to BC202 at elevated growth temperatures. Deletion of the cpxR gene from BC202 results in the loss of the ability of these supplements to restore growth at 42°C. Additionally, we report that the membrane potential of BC202 is significantly reduced and that cell division and growth can be restored either by expression of the multidrug transporter MdfA from a multicopy plasmid or by growth at pH 6.0. Together, these results suggest that the DedA family proteins YqjA and YghB are required for general envelope maintenance and homeostasis of the proton motive force under a variety of growth conditions

New Functions for the Ancient DedA Membrane Protein Family

The DedA protein family is a highly conserved and ancient family of membrane proteins with representatives in most sequenced genomes, including those of bacteria, archaea, and eukarya. The functions of the DedA family proteins remain obscure. However, recent genetic approaches have revealed important roles for certain bacterial DedA family members in membrane homeostasis. Bacterial DedA family mutants display such intriguing phenotypes as cell division defects, temperature sensitivity, altered membrane lipid composition, elevated envelope-related stress responses, and loss of proton motive force. The DedA family is also essential in at least two species of bacteria: Borrelia burgdorferi and Escherichia coli. Here, we describe the phylogenetic distribution of the family and summarize recent progress toward understanding the functions of the DedA membrane protein family

Product quality or market regulation? Explaining the slow growth of Europe's wine cooperatives, 1880-1980

Wine cooperatives were relatively scarce in Europe before the Second World War, but by the 1980s accounted for more than half of all wines made in France, Italy, and Spain, the three major producer countries. Unlike Danish dairy cooperatives, whose success before the First World War was linked to their ability to improve product quality and compete in high-value niche markets, wine cooperatives are often associated with the production of large volumes of low-quality products. This article argues that the initial slow diffusion of wine cooperatives was caused by the difficulties of improving quality due to environmental conditions in European vineyards (terroir') and measurement problems, rather than institutional shortcomings. Cooperatives only became widespread when the state found them a useful instrument to regulate markets, especially after 1950. The problems associated with poor wine quality were never resolved, and cooperatives have become increasingly uncompetitive in the market place, especially following the major decline in per capita consumption and shift towards premium wines from the 1980s.Financial assistance was provided by the Spanish government (ECO2012-36213) and Fundación Ramón Areces (‘Desigualdad and Conflicto’ Project)