ALBERT

Description: Multidrug resistance, strong side effects, and compliance problems in TB chemotherapy mandate new ways to kill Mycobacterium tuberculosis (Mtb). Here we show that deletion of the gene encoding homoserine transacetylase (metA) inactivates methionine and S-adenosylmethionine (SAM) biosynthesis in Mtb and renders this pathogen exquisitely sensitive to killing in immunocompetent or...

Description: Forests under novel environmental conditions (e.g., climate change), reintroduced species and modified disturbance regimes (e.g., exotic insect pests) with no analog in the past require mechanistic models to robustly project future forest dynamics. We used a forest landscape model based on physiological first principles to test hypotheses about the interactions among climate change, disturbance and land type on nascent efforts to restore blight –resistant American chestnut in the eastern U.S. Climate change should favor chestnut, but chestnut restoration will only modestly increase carbon stocks. Chestnut restoration will likely decrease both compositional and structural richness because chestnut will displaced some species. Abstract American chestnut (Castanea dentata) was once an important component forests in the central Appalachians (USA), but it was functionally extirpated nearly a century ago. Attempts are underway to reintroduce blight‐resistant chestnut to its former range, but it is uncertain how current forest composition, climate, and atmospheric changes and disturbance regimes will interact to determine future forest dynamics and ecosystem services. The combination of novel environmental conditions (e.g. climate change), a reintroduced tree species and new disturbance regimes (e.g. exotic insect pests, fire suppression) have no analog in the past that can be used to parameterize phenomenological models. We therefore used a mechanistic approach within the LANDIS‐II forest landscape model that relies on physiological first principles to project forest dynamics as the outcome of competition of tree cohorts for light and water as a function of temperature, precipitation, CO2 concentration, and life history traits. We conducted a factorial landscape simulation experiment to evaluate specific hypotheses about future forest dynamics in two study sites in the center of the former range of chestnut. Our results supported the hypotheses that climate change would favor chestnut because of its optimal temperature range and relative drought resistance, and that chestnut would be less competitive in the more mesic Appalachian Plateau province because competitors will be less stressed. The hypothesis that chestnut will increase carbon stocks was supported, although the increase was modest. Our results confirm that aggressive restoration is needed regardless of climate and soils, and that increased aggressiveness of chestnut restoration increased biomass accumulation. The hypothesis that chestnut restoration will increase both compositional and structural richness was not supported because chestnut displaced some species and age cohorts. Although chestnut restoration did not markedly enhance carbon stocks, our findings provide hope that this formerly important species can be successfully reintroduced and associated ecosystem services recovered.

Description: Klebsiella pneumoniae has become one of the most dangerous causative agents of hospital infections due to the acquisition of resistance to carbapenems, one of the last resort families of antibiotics. Resistance is usually mediated by carbapenemases coded for by different classes of genes. A prolonged outbreak of carbapenem-resistant K. pneumoniae infections has been recently described in northeastern Ohio. Most strains isolated from patients during this outbreak belong to MLST sequence type 258 (ST258). To understand more about this outbreak two isolates (strains 140 and 677), one of them responsible for a fatal infection, were selected for genome comparison analyses. Whole genome map and sequence comparisons demonstrated that both strains are highly related showing 99% average nucleotide identity. However, the genomes differ at the so-called high heterogeneity zone (HHZ) and other minor regions. This study identifies the potential value of the HHZ as a potential marker for K. pneumoniae clinical and epidemiological studies.

Description: The commercially important plants in the genus Cyclopia spp. are indigenous to the Cape Floristic Region of South Africa and are used to manufacture an herbal tea known as honeybush tea. Growing in the low nutrient fynbos soils, these plants are highly dependent on symbiotic interactions with soil microorganisms for nutrient acquisition. The aim of this study was to investigate the soil bacterial communities associated with two commercially important Cyclopia species, namely C. subternata and C. longifolia . Specific interest was the differences between rhizosphere and bulk soil collected from natural sites and commercially grown plants. Samples were collected on two occasions to include a dry summer and wet winter season. Results showed that the dominant bacterial taxa associated with these plants included Acidobacteria, Actinobacteria, Bacteroidetes and Proteobacteria. Commercial and natural as well as rhizosphere and bulk soil samples were highly similar in bacterial diversity and species richness. Significant differences were detected in bacterial community structures and co-occurrence patterns between the wet and dry seasons. The results of this study improved our knowledge on what effect commercial Cyclopia plantations and seasonal changes can have on soil bacterial communities within the endemic fynbos biome.

Description: Macromolecular crowding in biological media is an essential factor for cellular function. The interplay of intermolecular interactions at multiple time and length scales governs a fine-tuned system of reaction and transport processes, including particularly protein diffusion as a limiting or driving factor. Using quasielastic neutron backscattering, we probe the protein self-diffusion in crowded aqueous solutions of bovine serum albumin on nanosecond time and nanometer length scales employing the same protein as crowding agent. The measured diffusion coefficient D(φ) strongly decreases with increasing protein volume fraction φ explored within 7% ≤ φ ≤ 30%. With an ellipsoidal protein model and an analytical framework involving colloid diffusion theory, we separate the rotational Dr(φ) and translational Dt(φ) contributions to D(φ). The resulting Dt(φ) is described by short-time self-diffusion of effective spheres. Protein self-diffusion at biological volume fractions is found to be slowed down to 20% of the dilute limit solely due to hydrodynamic interactions.

Description: Canadian Journal of Forest Research, e-First Articles. Animal herbivory is a major limiting factor to successful oak (Quercus spp.) regeneration. Although bare-root seedlings are the most commonly used nursery stock type for oak plantings in the eastern United States, container seedlings may better resist planting stress and help enable seedlings to overcome browsing pressure. Four stock types (1 + 0 bare-root seedlings and seedlings in 164, 336, and 520 mL containers) of northern red oak (Quercus rubra L.) were planted on two reforestation sites in Indiana, USA, which were fenced to exclude white-tailed deer (Odocoileus virginianus Zimmerman). Seedlings were then subjected to three simulated browsing treatments (control unclipped, dormant clipped, and summer clipped). Container seedlings exhibited higher relative growth rates on both sites; for example, at one site, control seedlings in 336 mL containers had relative height growth of 558% compared with 79% for bare-root control seedlings. On both sites, summer-browsed seedlings of all stock types had negligible height growth, and summer browsing reduced survival at one site by 23% for all stock types compared with control seedlings. Browsing of seedlings during the dormant period did not affect growth for any stock type. Container seedlings may help facilitate rapid establishment of planted oak seedlings, but browse protection is necessary to ensure oak regeneration success in areas of large populations of deer.