Microbial resistance of Salmonella agona from various regions of Brazil

The object of the investigation was the evaluation of the susceptibility to antibiotic and chemotherapeutic agents of 240 strains of Salmonella agona isolated from different sources (human, food and environment) obtained from five Brazilian states (Minas Gerais, S?o Paulo, Rio de Janeiro, Pernambuco and Rio Grande do Sul). The presence of R factors in 26 representative strains of the sample was also determined.     

Redox control of calcineurin by targeting the binuclear Fe(2+)-Zn(2+) center at the enzyme active site.

The interaction of protein serine/threonine phosphatase calcineurin (CaN) with superoxide and hydrogen peroxide was investigated. Superoxide specifically inhibited phosphatase activity of CaN toward RII (DLDVPIPGRFDRRVSVAAE) phosphopeptide in tissue and cell homogenates as well as the activity of the enzyme purified under reducing conditions. Hydrogen peroxide was an effective inhibitor of CaN at concentrations several orders of magnitude higher than superoxide. Inhibition by superoxide was calcium/calmodulin-dependent. Nitric oxide (NO) antagonized superoxide action on CaN. We provide kinetic and spectroscopic evidence that native, catalytically active CaN has a Fe(2+)-Zn(2+) binuclear center in its active site that is oxidized to Fe(3+)-Zn(2+) by superoxide and hydrogen peroxide. This oxidation is accompanied by a gain of manganese dependence of enzyme activity. CaN isolated by a conventional purification procedure was found in the oxidized, ferric enzyme form, and it became increasingly dependent on divalent cations. These results point to a complex redox regulation of CaN phosphatase activity by superoxide, which is modified by calcium, NO, and superoxide dismutase.     

Protection of Bacillus subtilis against cold stress via compatible-solute acquisition

Accumulation of compatible solutes is a strategy widely employed by bacteria to achieve cellular protection against high osmolarity. These compounds are also used in some microorganisms as thermostress protectants. We found that Bacillus subtilis uses the compatible solute glycine betaine as an effective cold stress protectant. Glycine betaine strongly stimulated growth at 15°C and permitted cell proliferation at the growth-inhibiting temperature of 13°C. Initial uptake of glycine betaine at 15°C was low but led eventually to the buildup of an intracellular pool whose size was double that found in cells grown at 35°C. Each of the three glycine betaine transporters (OpuA, OpuC, and OpuD) contributed to glycine betaine accumulation in the cold. Protection against cold stress was also accomplished when glycine betaine was synthesized from its precursor choline. Growth of a mutant defective in the osmoadaptive biosynthesis for the compatible solute proline was not impaired at low temperature (15°C). In addition to glycine betaine, the compatible solutes and osmoprotectants l-carnitine, crotonobetaine, butyrobetaine, homobetaine, dimethylsulfonioactetate, and proline betaine all served as cold stress protectants as well and were accumulated via known Opu transport systems. In contrast, the compatible solutes and osmoprotectants choline-O-sulfate, ectoine, proline, and glutamate were not cold protective. Our data highlight an underappreciated facet of the acclimatization of B. subtilis to cold environments and allow a comparison of the characteristics of compatible solutes with respect to their osmotic, heat, and cold stress-protective properties for B. subtilis cells.     

Arg149 is involved in switching the low affinity, open state of the binding protein AfProX into its high affinity, closed state

The substrate binding protein AfProX from the Archaeoglobus fulgidus ProU ATP binding cassette transporter is highly selective for the compatible solutes glycine betaine (GB) and proline betaine, which confer thermoprotection to this hyperthermophilic archaeon. A detailed mutational analysis of the substrate binding site revealed the contribution of individual amino acids for ligand binding. Replacement of Arg149 by an Ala residue displayed the largest impact on substrate binding. The structure of a mutant AfProX protein (substitution of Tyr111 with Ala) in complex with GB was solved in the open liganded conformation to gain further insight into ligand binding. In this crystal structure, GB is bound differently compared to the GB closed liganded structure of the wild-type AfProX protein. We found that a network of amino acid side chains communicates the presence of GB toward Arg149, which increases ligand affinity and induces domain closure of AfProX. These results were corroborated by molecular dynamics studies and support the view that Arg149 finalizes the high-affinity state of the AfProX substrate binding protein.     

Association mapping for quality traits in soft winter wheat

Improvement of end-use quality in bread wheat (Triticum aestivum L.) depends on a thorough understanding of the genetic basis of important quality traits. The main goal of our study was to investigate the genetic basis of 1,000-kernel weight, protein content, sedimentation volume, test weight, and starch concentration using an association mapping approach. We fingerprinted 207 diverse European elite soft winter wheat lines with 115 SSR markers and evaluated the genotypes in multi-environment trials. The principal coordinate analysis revealed absence of a clear population but presence of a family structure. Therefore, we used linear mixed models and marker-based kinship matrices to correct for family structure. In genome-wide scans, we detected main effect QTL for all five traits. In contrast, epistatic QTL were only observed for sedimentation volume and test weight explaining a small proportion of the genotypic variation. Consequently, our findings suggested that integrating epistasis in marker-assisted breeding will not lead to substantially increased selection gain for quality traits in soft winter wheat.     

Artefact reduction for cell migration visualization using spectral domain optical coherence tomography

Visualization of cell migration during chemotaxis using spectral domain optical coherence tomography (OCT) requires non‐standard processing techniques. Stripe artefacts and camera noise floor present in OCT data prevent detailed computer‐assisted reconstruction and quantification of cell locomotion. Furthermore, imaging artefacts lead to unreliable results in automated texture based cell analysis. Here we characterize three pronounced artefacts that become visible when imaging sample structures with high dynamic range, e.g. cultured cells: (i) time‐varying fixed‐pattern noise; (ii) stripe artefacts generated by background estimation using tomogram averaging; (iii) image modulations due to spectral shaping. We evaluate techniques to minimize the above mentioned artefacts using an 800 nm optical coherence microscope. Effect of artefact reduction is shown exemplarily on two cell cultures, i.e. Dictyostelium on nitrocellulose substrate, and retinal ganglion cells (RGC‐5) cultured on a glass coverslip. Retinal imaging also profits from the proposed processing techniques. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Causes and consequences of past and projected Scandinavian summer temperatures, 500-2100 AD

Tree rings dominate millennium-long temperature reconstructions and many records originate from Scandinavia, an area for which the relative roles of external forcing and internal variation on climatic changes are, however, not yet fully understood. Here we compile 1,179 series of maximum latewood density measurements from 25 conifer sites in northern Scandinavia, establish a suite of 36 subset chronologies, and analyse their climate signal. A new reconstruction for the 1483-2006 period correlates at 0.80 with June-August temperatures back to 1860. Summer cooling during the early 17th century and peak warming in the 1930s translate into a decadal amplitude of 2.9°C, which agrees with existing Scandinavian tree-ring proxies. Climate model simulations reveal similar amounts of mid to low frequency variability, suggesting that internal ocean-atmosphere feedbacks likely influenced Scandinavian temperatures more than external forcing. Projected 21st century warming under the SRES A2 scenario would, however, exceed the reconstructed temperature envelope of the past 1,500 years.