Cold-Sensitive Pseudomonas RNA Polymerase I. Characterization of the Host Dependent Cold-Sensitive Restriction of Phage CB3

Analysis of bacteriophage CB3 infection of Pseudomonas aeruginosa strain PAT2 establishes that phage induced changes in net macromolecular synthesis are absent at nonpermissive phage growth temperatures (32 C). Alterations which are evident in the PAT2 strain at 37 C or in the fully permissive strain, PAO1C, at either warm or cold temperatures do not occur in PAT2 at low temperatures. CB3 DNA synthesis and the degradation of host DNA to approximately 78S components occur at 37 C, but are absent in PAT2 at 20 C. Nevertheless, attachment of phage DNA to host cytoplasmic material occurs under permissive and nonpermissive conditions. This binding of phage DNA at 20 C is identical in nature to phage DNA bound at 37 C. Thus, the conditional cold-sensitive PAT2 host function in the growth of CB3 is expressed subsequent to membrane binding of the infecting genomes but prior to the onset of the initiation of CB3 DNA synthesis, the inhibition of host DNA synthesis, and the transient depression in RNA synthesis which occurs in permissive cells.     

Marked host specificity and lack of phylogeographic population structure of Campylobacter jejuni in wild birds

Zoonotic pathogens often infect several animal species, and gene flow among populations infecting different host species may affect the biological traits of the pathogen including host specificity, transmissibility and virulence. The bacterium Campylobacter jejuni is a widespread zoonotic multihost pathogen, which frequently causes gastroenteritis in humans. Poultry products are important transmission vehicles to humans, but the bacterium is common in other domestic and wild animals, particularly birds, which are a potential infection source. Population genetic studies of C. jejuni have mainly investigated isolates from humans and domestic animals, so to assess C. jejuni population structure more broadly and investigate host adaptation, 928 wild bird isolates from Europe and Australia were genotyped by multilocus sequencing and compared to the genotypes recovered from 1366 domestic animal and human isolates. Campylobacter jejuni populations from different wild bird species were distinct from each other and from those from domestic animals and humans, and the host species of wild bird was the major determinant of C. jejuni genotype, while geographic origin was of little importance. By comparison, C. jejuni differentiation was restricted between more phylogenetically diverse farm animals, indicating that domesticated animals may represent a novel niche for C. jejuni and thereby driving the evolution of those bacteria as they exploit this niche. Human disease is dominated by isolates from this novel domesticated animal niche.     

State-space analysis of time-varying higher-order spike correlation for multiple neural spike train data

Precise spike coordination between the spiking activities of multiple neurons is suggested as an indication of coordinated network activity in active cell assemblies. Spike correlation analysis aims to identify such cooperative network activity by detecting excess spike synchrony in simultaneously recorded multiple neural spike sequences. Cooperative activity is expected to organize dynamically during behavior and cognition; therefore currently available analysis techniques must be extended to enable the estimation of multiple time-varying spike interactions between neurons simultaneously. In particular, new methods must take advantage of the simultaneous observations of multiple neurons by addressing their higher-order dependencies, which cannot be revealed by pairwise analyses alone. In this paper, we develop a method for estimating time-varying spike interactions by means of a state-space analysis. Discretized parallel spike sequences are modeled as multi-variate binary processes using a log-linear model that provides a well-defined measure of higher-order spike correlation in an information geometry framework. We construct a recursive Bayesian filter/smoother for the extraction of spike interaction parameters. This method can simultaneously estimate the dynamic pairwise spike interactions of multiple single neurons, thereby extending the Ising/spin-glass model analysis of multiple neural spike train data to a nonstationary analysis. Furthermore, the method can estimate dynamic higher-order spike interactions. To validate the inclusion of the higher-order terms in the model, we construct an approximation method to assess the goodness-of-fit to spike data. In addition, we formulate a test method for the presence of higher-order spike correlation even in nonstationary spike data, e.g., data from awake behaving animals. The utility of the proposed methods is tested using simulated spike data with known underlying correlation dynamics. Finally, we apply the methods to neural spike data simultaneously recorded from the motor cortex of an awake monkey and demonstrate that the higher-order spike correlation organizes dynamically in relation to a behavioral demand.     

Spatial, temporal, and species variation in prevalence of influenza A viruses in wild migratory birds

Although extensive data exist on avian influenza in wild birds in North America, limited information is available from elsewhere, including Europe. Here, molecular diagnostic tools were employed for high-throughput surveillance of migratory birds, as an alternative to classical labor-intensive methods of virus isolation in eggs. This study included 36,809 samples from 323 bird species belonging to 18 orders, of which only 25 species of three orders were positive for influenza A virus. Information on species, locations, and timing is provided for all samples tested. Seven previously unknown host species for avian influenza virus were identified: barnacle goose, bean goose, brent goose, pink-footed goose, bewick's swan, common gull, and guillemot. Dabbling ducks were more frequently infected than other ducks and Anseriformes; this distinction was probably related to bird behavior rather than population sizes. Waders did not appear to play a role in the epidemiology of avian influenza in Europe, in contrast to the Americas. The high virus prevalence in ducks in Europe in spring as compared with North America could explain the differences in virus-host ecology between these continents. Most influenza A virus subtypes were detected in ducks, but H13 and H16 subtypes were detected primarily in gulls. Viruses of subtype H6 were more promiscuous in host range than other subtypes. Temporal and spatial variation in influenza virus prevalence in wild birds was observed, with influenza A virus prevalence varying by sampling location; this is probably related to migration patterns from northeast to southwest and a higher prevalence farther north along the flyways. We discuss the ecology and epidemiology of avian influenza A virus in wild birds in relation to host ecology and compare our results with published studies. These data are useful for designing new surveillance programs and are particularly relevant due to increased interest in avian influenza in wild birds.     

The crystal structure of the apoenzyme of the iron-sulphur cluster-free hydrogenase

The iron-sulphur cluster-free hydrogenase (Hmd, EC 1.12.98.2) from methanogenic archaea is a novel type of hydrogenase that tightly binds an iron-containing cofactor. The iron is coordinated by two CO molecules, one sulphur and a pyridone derivative, which is linked via a phosphodiester bond to a guanosine base. We report here on the crystal structure of the Hmd apoenzyme from Methanocaldococcus jannaschii at 1.75 A and from Methanopyrus kandleri at 2.4 A resolution. Homodimeric Hmd reveals a unique architecture composed of one central and two identical peripheral globular units. The central unit is composed of the intertwined C-terminal segments of both subunits, forming a novel intersubunit fold. The two peripheral units consist of the N-terminal domain of each subunit. The Rossmann fold-like structure of the N-terminal domain contains a mononucleotide-binding site, which could harbour the GMP moiety of the cofactor. Another binding site for the iron-containing cofactor is most probably Cys176, which is located at the bottom of a deep intersubunit cleft and which has been shown to be essential for enzyme activity. Adjacent to the iron of the cofactor modelled as a ligand to Cys176, an extended U-shaped extra electron density, interpreted as a polyethyleneglycol fragment, suggests a binding site for the substrate methenyltetrahydromethanopterin.     

Adipose Tissue-Derived Stem Cells Reduce Acute and Chronic Kidney Damage in Mice

Acute and chronic kidney injuries (AKI and CKI) constitute syndromes responsible for a large part of renal failures, and are today still associated with high mortality rates. Given the lack of more effective therapies, there has been intense focus on the use stem cells for organ protective and regenerative effects. Mesenchymal stem cells (MSCs) have shown great potential in the treatment of various diseases of immune character, although there is still debate on its mechanism of action. Thus, for a greater understanding of the role of MSCs, we evaluated the effect of adipose tissue-derived stem cells (AdSCs) in an experimental model of nephrotoxicity induced by folic acid (FA) in FVB mice. AdSC-treated animals displayed kidney functional improvement 24h after therapy, represented by reduced serum urea after FA. These data correlated with cell cycle regulation and immune response modulation via reduced chemokine expression and reduced neutrophil infiltrate. Long-term analyses, 4 weeks after FA, indicated that AdSC treatment reduced kidney fibrosis and chronic inflammation. These were demonstrated by reduced interstitial collagen deposition and tissue chemokine and cytokine expression. Thus, we concluded that AdSC treatment played a protective role in the framework of nephrotoxic injury via modulation of inflammation and cell cycle regulation, resulting in reduced kidney damage and functional improvement, inhibiting organ fibrosis and providing long-term immune regulation.     

Carbon isotopic fractionation in heterotrophic microbial metabolism.

Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4% depleted in 13C relative to the glucose used as the carbon source, whereas the acetate was 12.3% enriched in 13C. The acetate 13C enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6% depleted in 13C, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7%, respectively. Aspartic and glutamic acids were -1.6 and +2.7%, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle.