Inhibition of virulence gene expression in Staphylococcus aureus by novel depsipeptides from a marine photobacterium

During a global research expedition, more than five hundred marine bacterial strains capable of inhibiting the growth of pathogenic bacteria were collected. The purpose of the present study was to determine if these marine bacteria are also a source of compounds that interfere with the agr quorum sensing system that controls virulence gene expression in Staphylococcus aureus. Using a gene reporter fusion bioassay, we recorded agr interference as enhanced expression of spa, encoding Protein A, concomitantly with reduced expression of hla, encoding α-hemolysin, and rnaIII encoding RNAIII, the effector molecule of agr. A marine Photobacterium produced compounds interfering with agr in S. aureus strain 8325-4, and bioassay-guided fractionation of crude extracts led to the isolation of two novel cyclodepsipeptides, designated solonamide A and B. Northern blot analysis confirmed the agr interfering activity of pure solonamides in both S. aureus strain 8325-4 and the highly virulent, community-acquired strain USA300 (CA-MRSA). To our knowledge, this is the first report of inhibitors of the agr system by a marine bacterium.     

The Forelimb and Hoof Conformation in a Population of Mongolian Horses

This article describes the lower limb and hoof conformation of a population of semi-feral Mongolian horses living on an open tundra/steppe environment. Data were collected from a convenience sample of 120 Mongolian horses used in the 2011 Mongolian Derby. Digital images of the hooves were obtained, and the lower limb conformation was assessed by four veterinarians involved in the screening of the horses offered for the derby. The horses were predominantly geldings (96%, 100/104), approximately 8.6 ± 2.5 years old, and 137 ± 8 cm at the withers. None of the horses were subjected to routine hoof trimming. Based on a 7-point linear score, lower limb conformation was normal, with a trend (>1 linear score deviation) slightly toward carpal valgus, mildly offset cannon (third metacarpal), and valgus at the matacarpophalangeal joint. Hoof measurements were within the norm for horses of this size. Fetlock valgus was associated with a smaller hoof width:length ratio (P = .016). None of the other hoof measurements were significantly associated with abnormal conformation scores. Overall, few conformation abnormalities were observed, and hoof shape and size was within the normal expected range for horses of this size. The hoof conformation in this population of Mongolian horses represented the natural interaction of the hoof with the environment.     

Maternal l-arginine supplementation during early gestation affects foetal skeletal myogenesis in pigs

To study the impact of maternal l-arginine supplementation during early gestation on skeletal muscle formation in the offspring, gilts were fed 3 kg of a standard diet (control group, n=10) or standard diet and additionally 26 g/d l-arginine from d 14 to 28 of gestation (arginine group, n=10). The gilts were sacrificed at d 75 of gestation. From each litter the lightest, the heaviest, and one medium-weight foetus per sex were selected and three different muscle samples were collected. In the longissimus dorsi muscle of all foetuses (n=99) biochemical properties were assessed. In the same muscle of a subset of the lightest and heaviest female foetuses (n=28), mRNA expression of selected genes involved in myogenesis were measured. In all three muscles, myosin heavy chain (MyHC) expression analyses (n=99) were performed. The protein/DNA ratio tended to be lower (P=0.08) in the offspring of the arginine group. Treatment×sex interactions revealed lower creatine kinase activity (P<0.05) and protein concentration (P=0.07) in female's of the arginine group. The MYF5 mRNA expression was lower (P<0.01) in the lightest, whereas IGF2 and IGFBP5 expressions (P<0.001) were lower in the heaviest females of the arginine group. The proportion of MyHC mRNA expression revealed an increase in the embryonic isoform (P=0.05) and a decrease by tendency in the Slow/I and IIx isoforms (P<0.10) in response to arginine supplementation. The results suggest that arginine supplementation during early gestation stimulates myogenic proliferation and delays muscular differentiation at d 75 of gestation.     

Efficient measurement of amylose content in cereal grains

Rapid and economical measurement of amylose content in barley is important for genetic study and breeding improvement of this trait. Seventeen genotypes with a wide range of amylose contents were used to compare the amylose measurement accuracy of the cost-effective iodine–potassium iodide (I:KI) method to the commercially available enzyme-based Megazyme protocol. Comparable accuracy from I:KI was demonstrated in low amylose samples (below 10% dried base), as were limitations in regular or high amylose samples. To address the major cost of sample preparation in nutritional trait analysis, the I:KI method was also employed for amylose detection from β-glucan and free phosphate assay samples. Results indicated that samples used in β-glucan and phosphate assays could be further utilized for amylose measurement. Amylose detection accuracy using I:KI method from those assayed samples is comparable to that using the Megazyme method in low and regular amylose samples. Development of protocols for the double assays from one grain sample will significantly reduce the labor cost associated with sample preparation and will streamline the screening of early generation barley populations, where seed sample amounts are limited.     

Glyphosate uncouples gas exchange and chlorophyll fluorescence

BACKGROUND: Changes in chlorophyll fluorescence have often been advocated as a sensitive biomarker of plant stress, assuming that any kind of plant stress serious enough to affect plant growth will also affect photosynthesis. Glyphosate affects photosynthetic electron transport indirectly by inhibiting sink processes. The question is how fast this inhibition can be observed on CO₂ assimilation and ultimately on chlorophyll fluorescence? RESULTS: Experiments measuring CO₂ assimilation, conductance and chlorophyll fluorescence using four Kautsky curve parameters on barley (Hordeum vulgare L.) exposed to increasing doses of glyphosate showed a total cessation of CO₂ fixation and conductance without significant changes in chlorophyll fluorescence. The decrease in CO₂ fixation and conductance was significant 1 day after spraying and corresponded well to the decrease in biomass 5–7 days after spraying. CONCLUSION: A total cessation of CO₂ assimilation can take place without affecting chlorophyll fluorescence. Hypotheses concerning what happens to the energy from the photosynthetic apparatus that is not used for CO₂ assimilation are discussed. The results question the use of chlorophyll fluorescence as a universal indicator of stress on photosynthetic processes. Also, they demonstrate that changes in gas‐exchange parameters are more sensitive biomarkers for glyphosate toxicity compared with chlorophyll fluorescence. Copyright © 2010 Society of Chemical Industry     

微量元素与养猪生产

NRC矿物元素需求量的确定 了解猪的营养需求评估过程是至关重要的,这有助于理解我们所确定的猪的营养需求是否是当时最客观、最具代表性、最能反映当时科技水平的猪的营养需求。很明显,营养需求将随动物遗传改进的完善和科研的不断深入而发生变化,我们应了解猪在不同生产条件下的营养需求,并做出相应的调整。     

Forest composition,leaf litter,and songbird communities in oak- vs. maple-dominated forests in the eastern United States

Within the eastern deciduous forest region, forest composition varies, with some areas dominated by a mix of oaks (Quercus spp.) and other areas dominated by a mix of sugar maple (Acer saccharum) and other tree species. Prescribed fire is being used on an experimental basis to assess its effectiveness in restoring and maintaining oak-dominated forests. Maple-dominated forests are susceptible to invasion by non-native earthworms, such as Lumbricus terrestris, given the palatability of leaf litter and suitable soil conditions, especially in northern parts of the region. What are the implications of this variation on leaf litter availability and habitat for ground-nesting songbirds? We investigated this question by comparing forest composition, leaf litter, and songbird communities in maple-dominated forests in west-central Indiana and oak-dominated forests, recently burned and unburned, in southeastern Ohio. We also assessed abundance of earthworms and decomposition rates of different types of leaves in the maple-dominated forests in Indiana. Leaf litter and ground-nesting bird species were abundant in unburned oak-dominated forests, but were absent or nearly absent in recently burned oak-dominated forests and in maple-dominated forests. The lack of leaf litter and absence of ground-nesting bird species in maple-dominated forests may be due to the combination of abundant non-native earthworms, alkaline and calcium-rich soils, palatable leaves, and rapid leaf litter decomposition rates. Effects of burning on leaf litter and ground-nesting bird species in oak-dominated forests are probably temporary, as long as prescribed fires are not applied on a frequent or widespread basis. Our study is the first one to show a correlation between forest composition, leaf litter availability, earthworm abundance, and songbird populations. Many researchers are investigating effects of non-native earthworm invasions on ecosystem properties in eastern deciduous forests. We recommend that researchers should also monitor songbird populations to assess whether declines in ground-nesting bird populations are occurring in response to these changes.