Evolutionary Trade-Offs Underlie the Multi-faceted Virulence of Staphylococcus aureus.

Bacterial virulence is a multifaceted trait where the interactions between pathogen and host factors affect the severity and outcome of the infection. Toxin secretion is central to the biology of many bacterial pathogens and is widely accepted as playing a crucial role in disease pathology. To understand the relationship between toxicity and bacterial virulence in greater depth, we studied two sequenced collections of the major human pathogen Staphylococcus aureus and found an unexpected inverse correlation between bacterial toxicity and disease severity. By applying a functional genomics approach, we identified several novel toxicity-affecting loci responsible for the wide range in toxic phenotypes observed within these collections. To understand the apparent higher propensity of low toxicity isolates to cause bacteraemia, we performed several functional assays, and our findings suggest that within-host fitness differences between high- and low-toxicity isolates in human serum is a contributing factor. As invasive infections, such as bacteraemia, limit the opportunities for onward transmission, highly toxic strains could gain an additional between-host fitness advantage, potentially contributing to the maintenance of toxicity at the population level. Our results clearly demonstrate how evolutionary trade-offs between toxicity, relative fitness, and transmissibility are critical for understanding the multifaceted nature of bacterial virulence.

New insights into the structure of PAMAM dendrimer/gold nanoparticle nanocomposites.

In this work, we have employed a suite of complementary analytical techniques to shed light on the nanocomposite structures formed during gold nanoparticles (AuNPs) synthesis in the presence of poly(amidoamine) (PAMAM) dendrimers. Nanocomposites of AuNPs and either fourth or eighth generation amine-terminated PAMAM dendrimers (G4 or G8) were prepared. The size distributions of AuNPs and the nanocomposites were determined by transmission electron microscopy. Atomic force microscopy phase imaging and neutral impact collision ion scattering spectroscopy (NICISS) were utilized for the first time to investigate and compare nanocomposite structures formed from G4 and G8. Our results suggest that G4 stabilized the AuNP by capping the AuNP particle surface but that a certain fraction of the gold surface was still barely covered. In contrast, the metal nanoparticle surface was completely covered by G8. In addition, NICISS results provided evidence that nanocomposites deformed when being deposited directly onto a substrate.

Alternative Formulations of Trap Lures for Operational Detection, Population Monitoring, and Outbreak Forecasting of Southern Pine Beetle in the United States.

The southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is a major destructive pest of Pinus L. In the southeastern United States, numbers of this species and a major predator, Thanasimus dubius (Fabricius) (Coleoptera: Cleridae), captured during an annual springtime trapping survey are used to make forecasts of the likelihood and severity of an outbreak during the following summer. We investigated responses by both species to six lure formulations to evaluate their suitability for the survey and allow integration of historical data sets produced with differing lure compositions. Trapping trials were performed at four locations across three states (Louisiana, Mississippi, and Alabama) during spring, and at these and one additional location (North Carolina) in fall 2016. All lures included the pheromone component frontalin. Southern pine beetle preferred lures that additionally included the pheromone component endo-brevicomin and turpentine as a source of host odors (rather than a 7:3 mixture of monoterpenes alpha- and beta-pinene). Thanasimus dubius displayed little discrimination among lure compositions. Lure preferences by southern pine beetle did not differ significantly among locations in spring but were influenced by season. Gas chromatography (GC)-electroantennographic detection analyses with southern pine beetle and GC-mass spectrometry identified numerous known and potential semiochemicals that distinguished volatiles released by the tested host odor devices. The lure combination that included endo-brevicomin and alpha/beta-pinene is recommended for the trapping survey because of its high sensitivity for southern pine beetle and potential for greater data integrity resulting from its reproducible composition.

Response of Tomicus yunnanensis (Coleoptera: Scolytinae) to infested and uninfested Pinus yunnanensis bolts.

Tomicus yunnanensis Kirkendall and Faccoli (Coleoptera: Curculionidae: Scolytinae) is a newly described pine shoot beetle found in southwestern China. This beetle has affected >200,000 ha of Pinus yunnanensis (Franchet) forests over the past 30 yr. After maturation feeding in the shoots, adults attack the boles in December to produce a new generation. A hanging bolt study was initiated in November 2006 to detect the beetle flight patterns and to test if dispersing beetles respond to infested and uninfested material. Treatments tested were females only, males only, male and female pairs, and uninfested bolts. Beetles were collected on the bolts between 9:30 and 18:30, with peak catch in the afternoon between 14:00 and 18:30. No beetles were collected during the dark. Though trunk attacksin the field were observed in November, beetles were first collected on the bolts in January. No beetles were captured after March. Differences in numbers of beetles collected between treatments with infested bolts varied by month, but uninfested bolts always attracted fewer adults.

Electrophysiological and behavioral responses of Dendroctonus valens (Coleoptera: Curculionidae: Scolytinae) to four bark beetle pheromones.

The red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Curculionidae: Scolytinae), has caused extensive mortality of Pinus tabuliformis Carrière in north central China. The electrophysiological and behavioral activities of the four bark beetle pheromones, frontalin, exo-brevicomin, trans-verbenol, and cis-verbenol, singly or in combination with host-produced kairomones, were tested on red turpentine beetles. Both sexes showed a consistent electrophysiological response to the four test compounds. In Y-tube olfactometer bioassays, walking red turpentine beetles selected the host compound (+)-3-carene over any of the test compounds, but significantly higher numbers chose each tested pheromone over a blank control. The four compounds, tested singly or in combination, were not attractive to red turpentine beetles in field trapping studies in 2006 and 2007 and also did not significantly increase trap catch when combined with (+)-3-carene. Frontalin, alone or in combination with exo-brevicomin and trans-verbenol, significantly reduced the attractiveness of (+)-3-carene in 2006 but not in 2007. The possible roles of the pheromones in host and mate finding and selection are discussed.

Efficacy of two systemic insecticides injected into loblolly pine for protection against southern pine bark beetles (Coleoptera: Curculionidae).

We evaluated the efficacy of systemic insecticides emamectin benzoate and fipronil for preventing mortality of individual loblolly pines, Pinus taeda L., as a result of attacks by southern pine bark beetles (Coleoptera: Curculionidae, Scolytinae) for two consecutive years in Mississippi (2005-2006) and Alabama (2006-2007). Trees were injected once in the spring of 2005 (Mississippi) or 2006 (Alabama) and then were baited with species-specific bark beetle lures several weeks later. The southern pine beetle, Dendroctonus frontalis Zimmermann, was the target species but was changed to Ips spp. in Mississippi (but not Alabama) the second year because of few southern pine beetle attacks on baited trees. Single injections of emamectin benzoate were effective in reducing tree mortality caused by bark beetles compared with untreated checks. Although less effective overall, fipronil also significantly reduced tree mortality from southern pine beetle compared with the checks during the second year in Alabama. Tree mortality continued well after the lures had been removed. Evaluations of bolts taken from experimental trees killed in 2006 indicated that emamectin benzoate effectively prevented parent bark beetle gallery construction and that fipronil significantly reduced lengths of galleries constructed by adult beetles, brood development, and emergence, compared with checks. In contrast, neither insecticide treatment prevented the bark beetles from inoculating blue stain fungi, Ophiostoma spp., into treated trees.

Field response of Dendroctonus frontalis (Coleoptera: Scolytinae) to synthetic semiochemicals in Chiapas, Mexico.

Dendroctonus frontalis Zimmermann (Coleoptera: Scolytinae) is the most serious pest of pines (Pinus spp.) in Mexico. Conspecifics are attracted to trees undergoing colonization by the aggregation pheromone frontalin, which is synergized by odors of pine oleoresin released from beetle-damaged host tissue. Synthetic racemic frontalin combined with turpentine has been the operational bait used in traps for monitoring populations of D. frontalis in Mexico as well as the United States. Recently, racemic endo-brevicomin has been reported to be a synergist of the frontalin/turpentine bait and as an important component of the aggregation pheromone for D. frontalis populations in the United States. To determine whether racemic endo-brevicomin also might function as an aggregation synergist for the geographically isolated D. frontalis populations of Central America and Mexico, we performed a field trapping trial in Lagunas de Montebello National Park, Chiapas, Mexico, during July and August 2007. The combination of endo-brevicomin (placed either directly on the trap or 4 m away) plus racemic frontalin and turpentine caught at least 5 times more D. frontalis of both sexes than did turpentine either alone or in combination with either frontalin or endo-brevicomin. The addition of endo-brevicomin to the frontalin/turpentine bait also increased the proportion of females trapped. We conclude that the addition of endo-brevicomin might substantially improve the efficiency of the frontalin/turpentine bait for monitoring of D. frontalis in Central America and Mexico. We discuss factors that reconcile our results with previous studies that reported endo-brevicomin to be an attractant antagonist for populations of D. frontalis in Mexico and Honduras.

Predicting the Match Outcome in One Day International Cricket Matches, while the Game is in Progress.

Millions of dollars are wagered on the outcome of one day international (ODI) cricket matches, with a large percentage of bets occurring after the game has commenced. Using match information gathered from all 2200 ODI matches played prior to January 2005, a range of variables that could independently explain statistically significant proportions of variation associated with the predicted run totals and match outcomes were created. Such variables include home ground advantage, past performances, match experience, performance at the specific venue, performance against the specific opposition, experience at the specific venue and current form. Using a multiple linear regression model, prediction variables were numerically weighted according to statistical significance and used to predict the match outcome. With the use of the Duckworth-Lewis method to determine resources remaining, at the end of each completed over, the predicted run total of the batting team could be updated to provide a more accurate prediction of the match outcome. By applying this prediction approach to a holdout sample of matches, the efficiency of the "in the run "wagering market could be assessed. Preliminary results suggest that the market is prone to overreact to events occurring throughout the course of the match, thus creating brief inefficiencies in the wagering market. Key PointsIn excess of 80% of monies wagered on the outcome of ODI matches are placed after the match has commenced.Using all past data from ODI matches, multiple linear regression models are constructed to predict team totals and margin of victory.By combining match information with prediction models, an 'in the run' prediction process is created for ODI matches.

Statistical Analysis of Notational AFL Data Using Continuous Time Markov Chains.

Animal biologists commonly use continuous time Markov chain models to describe patterns of animal behaviour. In this paper we consider the use of these models for describing AFL football. In particular we test the assumptions for continuous time Markov chain models (CTMCs), with time, distance and speed values associated with each transition. Using a simple event categorisation it is found that a semi-Markov chain model is appropriate for this data. This validates the use of Markov Chains for future studies in which the outcomes of AFL matches are simulated. Key PointsA comparison of four AFL matches suggests similarity in terms of transition probabilities for events and the mean times, distances and speeds associated with each transition.The Markov assumption appears to be valid.However, the speed, time and distance distributions associated with each transition are not exponential suggesting that semi-Markov model can be used to model and simulate play.Team identified events and directions associated with transitions are required to develop the model into a tool for the prediction of match outcomes.

Home advantage in the Australian Football League.

The results of this study on home advantage in Australian rules football demonstrate that individual clubs have different home advantages. Traditional measures of home advantage as applied to whole competitions such as percentage of games won, and alternative measures such as average margin of victory for the home team, are calculated. Problems with these measures are discussed. Individual home advantages for each team are obtained using a linear model fitted to individual match margins; the resultant home advantages are analysed, and variations and possible causes or groupings of home advantage are proposed. It is shown that some models allowing different home advantages for different clubs are a significant improvement over previous models assuming a common home advantage. The results show a strong isolation effect, with non-Victorian teams having large home advantages, and lend support to the conclusion that crowd effects and ground familiarity are a major determinant of home advantage.