Genomic evidence for the evolution of Streptococcus equi : host restriction, increased virulence, and genetic exchange with human pathogens

The continued evolution of bacterial pathogens has major implications for both human and animal disease, but the exchange of genetic material between host-restricted pathogens is rarely considered. Streptococcus equi subspecies equi (S. equi) is a host-restricted pathogen of horses that has evolved from the zoonotic pathogen Streptococcus equi subspecies zooepidemicus (S. zooepidemicus). These pathogens share approximately 80% genome sequence identity with the important human pathogen Streptococcus pyogenes. We sequenced and compared the genomes of S. equi 4047 and S. zooepidemicus H70 and screened S. equi and S. zooepidemicus strains from around the world to uncover evidence of the genetic events that have shaped the evolution of the S. equi genome and led to its emergence as a host-restricted pathogen. Our analysis provides evidence of functional loss due to mutation and deletion, coupled with pathogenic specialization through the acquisition of bacteriophage encoding a phospholipase A(2) toxin, and four superantigens, and an integrative conjugative element carrying a novel iron acquisition system with similarity to the high pathogenicity island of Yersinia pestis. We also highlight that S. equi, S. zooepidemicus, and S. pyogenes share a common phage pool that enhances cross-species pathogen evolution. We conclude that the complex interplay of functional loss, pathogenic specialization, and genetic exchange between S. equi, S. zooepidemicus, and S. pyogenes continues to influence the evolution of these important streptococci.Publisher PDFPeer reviewe

Intermolecular interactions in the molecular ferromagnetic NH4Ni(mnt)(2)center dot H2O

Molecular solids that exhibit ferromagnetism are rare, and thus there is considerable interest in understanding the magnetic coupling mechanisms that operate in the few known examples(1). One such material is the charge-transfer salt NH4Ni(mnt)(2) . H2O, which consists of stacked planar metal ligands separated by ammonium cations. This salt is an insulator with localized spins that exhibit long-range ferromagnetic order at low temperatures (below 4.5 K)(2).3 Here we show that the Curie temperature demarcating the transition to the ferromagnetic state increases markedly with pressure until ferromagnetic order abruptly disappears at 6.8 kbar, indicating that the magnetic coupling is very sensitive to intermolecular separation. Using quantum-chemical calculations(3), we show that this pressure dependence arises from a competition between ferromagnetic coupling (resulting from nickel-sulphur intermolecular spin interactions), and antiferromagnetic coupling (from nickel-nickel interactions). We suggest that a similar interplay of spin-polarization effects might play a key role in determining the nature of the ground states (metallic, superconducting and so forth) observed in other molecular materials of this structural type(4,5)

Exploring the use of Near Infrared (NIR) Reflectance spectroscopy to predict starch pasting properties in whole grain barley

This study aimed to evaluate the ability of using near infrared reflectance (NIR) spectroscopy to predict parameters generated by the rapid visco analyser (RVA) in whole grain barley samples to further study starch pasting characteristics in a breeding program. A total of 130 whole grain barley samples from the University of Adelaide germplasm collection, harvested over three seasons (2009, 2010 and 2011) were analysed using both NIR and RVA instruments and calibrations developed using partial least squares (PLS) regression. The coefficient of determination in cross validation (R 2) and the standard error in cross validation (SECV) were 0.88 [SECV = 477.5 (RVU = rapid visco units)] for peak viscosity (PV), 0.82 (SECV = 635.5 RVU) for trough (THR), 0.92 (SECV = 190.4 RVU) for breakdown (BKD), 0.61 (SECV = 151.1 RVU) for setback (SET), 0.84 (SECV = 698.0 RVU) for final viscosity (FV), 0.70 (SECV = 0.54 s) for time to peak (TTP) and 0.36 (SECV = 2.2 min) for pasting temperature (PT). We have demonstrated that NIR spectroscopy shows promise as a rapid, non-destructive method to measure PV in whole grain barley. In this context, NIR spectroscopy has the potential to significantly reduce analytical time and cost for screening novel lines for starch properties for pasting properties.D. Cozzolino, S. Roumeliotis, J. Eglinto