ArgR is an essential local transcriptional regulator of the arcABC-operon in Streptococcus suis and crucial for biological fitness in acidic environment

Streptococcus suis is one of the most important pathogens in pigs and can also cause severe infections in humans. Despite its clinical relevance very little is known about the factors contributing to its virulence. Recently, we identified a new putative virulence factor in Streptococcus suis, the arginine deiminase system (ADS), an arginine catabolic enzyme system encoded by the arcABC-operon, which enables Streptococcus suis to survive in acidic environment. In this study, we focused on ArgR, an ADS associated regulator belonging to the ArgR/AhrC arginine repressor family. Using an argR knock-out strain we could show that ArgR is essential for arcABC-operon expression and necessary for the biological fitness of Streptococcus suis. By cDNA expression microarray analyses and quantitative real time RT-PCR we found that the arcABC-operon is the only gene cluster regulated by ArgR, which is in contrast to many other bacteria. Reporter gene analysis with gfp under the control of the arcABC promoter demonstrated that ArgR is able to activate the arcABC promoter. Electrophoretic mobility shift assays with fragments of the arcABC promoter and recombinant ArgR, and chromatin immunoprecipitation with antibodies directed against ArgR revealed that ArgR interacts with the arcABC promoter in vitro and in vivo by binding to a region from -147 to 72 bp upstream of the transcriptional start point. Overall our results show that in Streptococcus suis ArgR is an essential, system specific transcriptional regulator of the ADS directly interacting with the arcABC promoter in vivo

Cross Ratios of Quadrilateral Linkages

We discuss the cross-ratio map of planar quadrilateral linkages, also in the case when one of the links is telescopic. Most of our results are valid for a planar quadrilateral linkage with generic lengths of the sides. In particular, we describe the image of cross-ratio map for quadrilateral linkage and planar robot 3-arm.Comment: 12 pages,9 figures. March 2014: Proofs are added, typo's corrected; March 2015: Typo's correcte

B_s^0 - bar{B}_s^0 Mixing and the B_s -> J/psi phi Asymmetry in Supersymmetric Models

We analyse supersymmetric contributions to B_s mixing and their impact on mixing-induced CP asymmetries, using the mass insertion approximation. We discuss in particular the correlation of SUSY effects in the CP asymmetries of B_s -> J/psi phi and B_d -> phi K_S and find that the mass insertions dominant in B_s mixing and B_d -> phi K_S are (delta_{23}^d)_{LL, RR} and (delta_{23}^d)_{LR, RL}, respectively. We show that models with dominant (delta_{23}^d)_{LR, RL} can accomodate a negative value of S_{phi K_S}, in agreement with the BELLE measurement of that observable, but yield a B_s mixing phase too small to be observed. On the other hand, models with dominant (delta_{23}^d)_{LL, RR} predict sizeable SUSY contributions to both Delta M_s and the mixing phase, but do not allow the asymmetry in B_d -> phi K_S to become negative, except for small values of the average down squark mass, which, in turn, entail a value of Delta M_s too large to be observed at the Tevatron and the LHC. We conclude that the observation of B_s mixing at hadron machines, together with the confirmation of a negative value of S_{phi K_S}, disfavours models with a single dominant mass insertion.Comment: 17 pages, 5 figure