The influence of habitat quality on the foraging strategies of the entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis megidis

Entomopathogenic nematodes (EPN) are soil-transmitted parasites and their foraging strategies are believed to range from ‘ambush’ to ‘cruise’ foragers. However, research on their behaviour has not considered the natural habitat of these nematodes. We hypothesized that EPN behaviour would be influenced by soil habitat quality and tested this hypothesis using 2 EPN species Steinernema carpocapsae (an ‘ambusher’) and Heterorhabditis megidis (a ‘cruiser’) in 2 contrasting habitats, sand and peat. As predicted from previous studies, in sand most S. carpocapsae remained at the point of application and showed no taxis towards hosts, but in peat S. carpocapsae dispersed much more and showed a highly significant taxis towards hosts. H. megidis dispersed well in both media, but only showed taxis towards hosts in sand. In outdoor mesocosms in which both species were applied, S. carpocapsae outcompeted H. megidis in terms of host finding in peat, whereas the opposite was true in sand. Our data suggest that these 2 EPN may be habitat specialists and highlight the difficulties of studying soil-transmitted parasites in non-soil media

Rapid change in parasite infection traits over the course of an epidemic in a wild host-parasite population

By combining a field study with controlled laboratory experimentation, we examined how infection traits of the sterilizing bacterium, Pasteuria ramosa, changed over the course of a growing season in a natural population of its crustacean host Daphnia magna. The number of parasite transmission spores per infected host increased ten-fold over the course of the season, concomitant with a decline in the density of infected hosts. Plausible explanations for this variation include changes in environmental conditions, changes in host quality, or that parasite migration or natural selection caused a genetic change in the parasite population. We sought to distinguish some of these possibilities in a laboratory experiment. Thus, we preserved field-collected parasite spores throughout the season, and later exposed a set of hosts to a fixed dose of these spores under controlled laboratory conditions. Parasites collected late in the season were more infectious and grew more rapidly than parasites collected early in the season. This result is compatible with the hypothesis that the observed increase in infectivity in the field was due to genetic change, i.e. evolution in the P. ramosa population

Characterization of the recD gene of Neisseria gonorrhoeae MS11 and the Effect of recD Inactivation on Pilin Variation and DNA Transformation

Pilin antigenic variation in Neisseria gonorrhoeae may result following intrachromosomal recombination between homologous pi/ genes. Despite extensive study, recA is the only previously characterized gene known to be involved in this process. In this study, the gonococcal recD gene, encoding one subunit of the putative RecBCD holoenzyme, was characterized and its role in pilin variation assessed. The complete recD gene of N. gonorrhoeae M S l l was cloned and its nucleotide sequence determined. The gonococcal recD gene complemented a defined Escherichia coli recD mutant, based on plaque formation of bacteriophage 1 and the restoration of ATP-dependent nuclease activity. Inactivation of the gonococcal recD gene had no measurable effect on cell viability or survival following UV exposure, but did decrease the frequency of DNA transformation approximately threefold. The frequency at which nonparental pilin phenotypes were spawned was 12-fold greater in M S l l recD mutants compared with the parental MS11 re& strain. Similar results were obtained using recD mutants that were not competent for DNA transformation. Complementation of the M S l l recD mutant with a wild-type recD gene copy restored the frequency of pilin phenotypic variation to approximately wild-type levels. The nucleotide changes at pi/€ in the recD mutants were confined to the variable regions of the gene and were similar to changes previously attributed to gene conversion

Kiwi forego vison in the guidance of their nocturnal activities

We propose that the Kiwi visual system has undergone adaptive regression evolution driven by the trade-off between the relatively low rate of gain of visual information that is possible at low light levels, and the metabolic costs of extracting that information

The envelope gene of transmitted HIV-1 resists a late interferon gamma-induced block

Type I interferon (IFN) signaling engenders an antiviral state that likely plays an important role in constraining HIV-1 transmission and contributes to defining subsequent AIDS pathogenesis. Type II IFN (IFNγ) also induces an antiviral state but is often primarily considered to be an immunomodulatory cytokine. We report that IFNγ stimulation can induce an antiviral state that can be both distinct from that of type I interferon, and can potently inhibit HIV-1 in primary CD4+ T cells and a number of human cell lines. Strikingly, we find that transmitted/founder (TF) HIV-1 viruses can resist a late block that is induced by type II IFN, and the use of chimeric IFNγ- sensitive/resistant viruses indicates that interferon-resistance maps to the env gene. Simultaneously, in vitro evolution also revealed that just a single amino acid substitution in envelope can confer substantial resistance to IFN-mediated inhibition. Thus, the env gene of transmitted HIV-1 confers resistance to a late block that is phenotypically distinct from those previously described to be resisted by env, and is therefore mediated by unknown IFNγ-stimulated factor(s) in human CD4+ T cells and cell lines. This important unidentified block could play a key role in constraining HIV-1 transmission

Testing a Simplified Version of Einstein's Equations for Numerical Relativity

Solving dynamical problems in general relativity requires the full machinery of numerical relativity. Wilson has proposed a simpler but approximate scheme for systems near equilibrium, like binary neutron stars. We test the scheme on isolated, rapidly rotating, relativistic stars. Since these objects are in equilibrium, it is crucial that the approximation work well if we are to believe its predictions for more complicated systems like binaries. Our results are very encouraging.Comment: 9 pages (RevTeX 3.0 with 6 uuencoded figures), CRSR-107

On modeling player fitness in training for team sports with application to professional rugby

It is increasingly important for professional sports teams to monitor player fitness in order to optimize performance. Models have been put forward linking fitness in training to performance in competition but rely on regular measurements of player fitness. As formal tests for measuring player fitness are typically time-consuming and inconvenient, measurements are taken infrequently. As such, it may be challenging to accurately predict performance in competition as player fitness is unknown. Alternatively, other data, such as how the players are feeling, may be measured more regularly. This data, however, may be biased as players may answer the questions differently and these differences may dominate the data. Linear Mixed Methods and Support Vector Machines were used to estimate player fitness from available covariates at times when explicit measures of fitness are unavailable. Using data provided by a professional rugby club, a case study was used to illustrate the application and value of these models. Both models performed well with R^2 values ranging from 60% to 85%, demonstrating that the models largely captured the biases introduced by individual players

Regional assessment of the ground-water resources in eastern Kankakee and northern Iroquois counties

"ISWS/RI-111."--Cover.Includes bibliographical references (p. 60-61).Enumeration continues through succeeding title