Regulation of yeast replicative life span by TOR and Sch9 in response to nutrients

Calorie restriction increases life span in many organisms, including the budding yeast Saccharomyces cerevisiae. From a large-scale analysis of 564 single-gene-deletion strains of yeast, we identified 10 gene deletions that increase replicative life span. Six of these correspond to genes encoding components of the nutrient-responsive TOR and Sch9 pathways. Calorie restriction of tor1D or sch9D cells failed to further increase life span and, like calorie restriction, deletion of either SCH9 or TOR1 increased life span independent of the Sir2 histone deacetylase. We propose that the TOR and Sch9 kinases define a primary conduit through which excess nutrient intake limits longevity in yeast.     

A real-time polymerase chain reaction assay for quantification of Edwardsiella ictaluri in catfish pond water and genetic homogeneity of diagnostic case isolates from Mississippi

A quantitative polymerase chain reaction (qPCR) assay was developed for the detection and quantification of Edwardsiella ictaluri in channel catfish Ictalurus punctatus pond water using modifications to a published E. ictaluri-specific qPCR assay and previously established protocols for the molecular detection of myxozoan parasites in catfish ponds. Genomic DNA equivalents indicative of the number of bacteria in a sample were determined and standard curves correlating to bacterial numbers were established. The assay was found to be highly repeatable and reproducible, with a linear dynamic range of five orders of magnitude. There was no interference of the assay from the presence of large quantities of nontarget DNA. Known quantities of bacteria were added to sample volumes of 40 or 500 mL of pond water collected from several different ponds. The minimum level of detection was approximately 100 cell equivalents (CE) in 40 (2.5 CE/mL) or 500 mL of pond water (0.2 CE/mL). Sample volumes of 40 mL yielded the most consistent results, which were not significantly different from those obtained from broth culture alone. Cell equivalents determined by qPCR in 40-mL pond water samples spiked with known quantities of bacteria were within one order of magnitude of the actual number of cells added. Repetitive element-based polymerase chain reaction analysis of archived isolates demonstrated the genetic homogeneity of E. ictaluri, and consistent amplification of these isolates by qPCR analysis demonstrated the stability of the PCR target. The assay described here provides a reliable method for the detection and quantification of E. ictaluri in pond water and will be an invaluable tool in epidemiological studies. Additionally, the assay provides a way to evaluate the effects that vaccination, antibiotic treatments, and restricted feeding practices have on E. ictaluri populations during an outbreak. Information obtained with these tools will aid in optimizing disease management practices designed to maximize productivity while minimizing losses.     

Detection and spread of Phytophthora austrocedri within infected Juniperus communis woodland and diversity of co‐associated Phytophthoras as revealed by metabarcoding

Phytophthora austrocedri is a recently invasive soilborne pathogen which is causing widespread mortality of Juniperus communis in northern Britain. The pathways by which a single genotype of P. austrocedri has spread to infect such a geographically dispersed range of woodland sites within a relatively short timeframe are unknown. This study examined the detectability of P. austrocedri in soil and water within infected J. communis woodland using qPCR to gain a better understanding of the pathogen's key mechanisms of spread. A Phytophthora metabarcoding method was also applied to investigate the wider diversity of Phytophthora species present in water at one of the sites. qPCR analyses of P. austrocedri in soil samples at a J. communis woodland exhibiting low‐to‐moderate levels of disease suggested a slow natural spread of the pathogen in soil, requiring high moisture conditions. However, the ubiquity of P. austrocedri DNA in soil samples collected across a heavily infected J. communis site suggests that once established at a site the pathogen can be spread readily in soil locally, most likely vectored by animal movements and/or human activities. The hypothesis that P. austrocedri is aerially transmitted in rainwater was not adequately proven, and an alternative hypothesis for the widespread distribution of the pathogen on J. communis in northern Britain is presented. Metabarcoding identified DNA from a diverse range of Phytophthora species in river and rainwater samples although the main target pathogen, P. austrocedri, was not amplified which disagreed with some of the qPCR findings. Possible reasons for this are discussed.     

The influence of photoperiod on gonadotrophin-releasing hormone stimulated luteinising hormone release in the anoestrous mare

The transition from anoestrus to oestrus in mares is controlled by photoperiod. The present study examined whether additional daylength would accelerate the mares' response to gonadotrophin-releasing-hormone (GnRH). Nine anoestrous mares were placed under ambient or artificial long lighting on 7th January. The four month experimental period was divided into a three-day sequence which was repeated at 21 day intervals. Ovaries were palpated rectally on Day 1; saline was injected (1 ml intravenously [iv]) on Day 2; GnRH was administered (0.59 microgram/kg bodyweight iv) on Day 3. Blood was taken at -60, 0, 15, 30, 60 and 120 mins relative to saline or GnRH treatment. Serum luteinising hormone (LH) was determined by a homologous equine radioimmunoassay (RIA). Several criteria were employed to define a positive response to GnRH and the results were analysed by Fisher's exact probability test. Treatment with artificial light allowed a response to GnRH within six weeks whereas the mares in ambient lighting took 12 weeks to respond to GnRH. The advancement in the time of response to GnRH under the long photoperiod could be related to changes in pituitary LH content, accelerated follicular activity or alterations in other brain-pituitary hormone levels.     

Phenotypic and Genotypic Heterogeneity among Streptococcus iniae Isolates Recovered from Cultured and Wild Fish in North America,Central America and the Caribbean Islands

Abstract

Streptococcus iniae, the etiological agent of streptococcosis in fish, is an important pathogen of cultured and wild fish worldwide. During the last decade outbreaks of streptococcosis have occurred in a wide range of cultured and wild fish in the Americas and Caribbean islands. To gain a better understanding of the epizootiology of S. iniae in the western hemisphere, over 30 S. iniae isolates recovered from different fish species and geographic locations were characterized phenotypically and genetically. Species identities were determined biochemically and confirmed by amplification and sequencing of the 16S rRNA gene. Repetitive-element palindromic PCR fingerprinting as well as biochemical and antimicrobial susceptibility profiles suggest that a single strain of S. iniae was responsible for two different disease outbreaks among reef fishes in the Caribbean, one in 1999 and another in 2008. Interestingly, a majority of the isolates recovered from cultured fish in the Americas were genetically distinct from the Caribbean isolates and exhibited a trend toward higher minimal inhibitory concentration with respect to several antibiotics as well as greater genetic variability. The biological significance of this genetic variability is unclear, but it could have implications for future vaccine development and treatment.

Received April 20, 2014; accepted July 7, 2014     

Temperature and Precipitation Affect Steer Weight Gains Differentially by Stocking Rate in Northern Mixed-Grass Prairie

Cattle weight gain responses to seasonal weather variability are difficult to predict for rangelands because few long-term (>20 yr) studies have been conducted. However, an increased understanding of temperature and precipitation influences on cattle weight gains is needed to optimize stocking rates and reduce enterprise risk associated with climatic variability. Yearling steer weight gain data collected at the USDA-ARS High Plains Grasslands Research Station at light, moderate, and heavy stocking rates for 30 years (1982–2011) were used to examine the effects of spring (April–June) and summer (July–September) temperature and precipitation, as well as prior-growing-season (prior April–September) and fall/winter (October–March) precipitation, on beef production (kg · ha^?1). At heavier stocking rates, steer production was more sensitive to seasonal weather variations. A novel finding was that temperature (relatively cool springs and warm summers) played a large predictive role on beef production. At heavier stocking rates, beef production was highest during years with cool, wet springs and warm, wet summers, corresponding to optimum growth conditions for this mixed C₃–C₄ plant community. The novelty and utility of these findings may increase the efficacy of stocking rate decision support tools. The parsimonious model structure presented here includes three-month seasonal clusters that are forecasted and freely available from the US National Oceanic and Atmospheric Administration up to a year in advance. These seasonal weather forecasts can provide ranchers with an increased predictive capacity to adjust stocking rates (in advance of the grazing season) according to predicted seasonal weather conditions, thereby reducing enterprise risk.