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Roles of DegP in Prevention of Protein Misfolding in the Periplasm upon Overexpression of Penicillin Acylase in Escherichia coli. Kao-Lu Pan, 2003.Enhancement of the production of soluble recombinant penicillin acylase in Escherichia coli via coexpression of a periplasmic protease/chaperone, DegP, was demonstrated . Coexpression of DegP resulted in a shift of in vivo penicillin acylase (PAC) synthesis flux from the nonproductive pathway to the productive one when pac was overexpressed . The number of inclusion bodies, which consist primarily of protein aggregates of PAC precursors in the periplasm, was highly reduced, and the specific PAC activity was highly increased . DegP was a heat shock protein induced in response to pac overexpression, suggesting that the protein could possibly suppress the physiological toxicity caused by pac overexpression . Coexpression of DegPS210A, a DegP mutant without protease activity but retaining chaperone activity, could not suppress the physiological toxicity, suggesting that DegP protease activity was primarily responsible for the suppression, possibly by degradation of abnormal proteins when pac was overexpressed . However, a shortage of periplasmic protease activity was not the only reason for the deterioration in culture performance upon pac overexpression because coexpression of a DegP-homologous periplasmic protease, DegQ or DegS, could not suppress the physiological toxicity . The chaperone activity of DegP is proposed to be another possible factor contributing to the suppression . Clonality and Diversity of the Fish Pathogen Lactococcus garvieae in Mediterranean Countries. Marina Eyngor, 2004.Infection with Lactococcus garvieae is considered the most important risk factor for the European trout industry, and the losses are approximately 50% of the total production . To improve our understanding of the genetic links among strains originating from different countries, we examined the population structure of L . garvieae by comparing 81 strains isolated from different sources and ecosystems (41 farms in six countries) in which the bacterium is commonly found . Genetic similarities (as assessed with molecular tools, including restriction fragment length polymorphism ribotyping with two endonucleases) were compared with serological data . The combined results reveal that in endemic sites the bacterial population displays a clonal structure, whereas bacterial diversity characterizes sites where the infection is sporadic . The pst Operon of Bacillus subtilis Is Specifically Induced by Alkali Stress. Akram Atalla, 2003.To cope with a sudden increase in the external pH value to 8.9, Bacillus subtilis cells induce about 80 genes which can be divided into two classes . Most of these genes are members of the  W regulon, while some are under the control of so-far-unknown transcriptional regulators . The genes of the pst operon belong to the second class . Here, we attempted to answer the questions of why and how the genes of this operon are induced . Using transcriptional fusions to two of the five genes of this operon, we confirmed their induction after alkali stress . Furthermore, a Northern blot experiment revealed that the complete operon was alkali inducible, that the transcriptional start site used was identical to that used after phosphate starvation, and that induction was prevented in a phoR background . Most interestingly, increasing the phosphate concentration within the medium prevented alkali induction of the pst operon, and phoA, another member of the PhoRP regulon, did not respond to alkali stress . In the end, we showed that alkali treatment completely prevented phosphate uptake . These results are discussed to explain alkali induction of the pst operon .
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