Plasmid-Mediated Transference of Multiple-Antibiotic Resistance between Escherichia coli Isolates in the Western Montana Region

This thesis investigates the multiple drug resistant (MDR) characteristic within enteric Escherichia coli (E. coli) isolates and their ability to transfer this phenotype via resistant-plasmid (R-plasmid) conjugation. E. coli were isolated from bovine fecal samples in the western Montana region. These isolates were subjected to antibiotic resistance testing, then sorted and stored based on general resistance to two broad-spectrum antibiotics, ampicillin and chlorotetracycline. All isolates underwent molecular differentiation using RAPD PCR, then plasmid extraction using a Qiagen Maxi kit. These results were compared to determine if genetically similar isolates, as determined by RAPD PCR, were more likely to contain a plasmid. Isolates containing a plasmid were subjected to conjugation assays to determine transferability of plasmids. In the conjugation assay, each MDR donor isolate was mated with azide-resistant strain, J53AZr. The following hypotheses were addressed: 1) a strain of E. coli will demonstrate a MDR pattern with resistance to more antibiotics if a plasmid is present and 2) the ability to transfer the MDR characteristic to other strains lacking the plasmid is specific to the donor strain of E. coli and its MDR pattern designated by a plasmid. Plasmid presence in E. coli isolates increased with level of MDR. Results also demonstrated plasmid conjugation between E. coli isolates was more likely to occur as level of MDR increased; however the conjugation assay may require larger sample size to confirm the trend. The RAPD PCR method should also be altered to illustrate more accurate banding patterns and verify molecular differences between strains containing plasmids

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Effects of aging on timing of hibernation and reproduction

Small hibernators are long-lived for their size because seasonal dormancy greatly reduces predation risk. Thus, within a year, hibernators switch between states of contrasting mortality risk (active season versus hibernation), making them interesting species for testing the predictions of life-history theory. Accordingly, we hypothesized that, with advancing age and hence diminishing reproductive potential, hibernators should increasingly accept the higher predation risk associated with activity to increase the likelihood of current reproductive success. For edible dormice (Glis glis) we show that age strongly affects hibernation/activity patterns, and that this occurs via two pathways: (i) with increasing age, dormice are more likely to reproduce, which delays the onset of hibernation, and (ii) age directly advances emergence from hibernation in spring. We conclude that hibernation has to be viewed not merely as an energy saving strategy under harsh climatic conditions, but as an age-affected life-history trait that is flexibly used to maximize fitness

Hibernation is associated with increased survival and the evolution of slow life histories among mammals

Survival probability is predicted to underlie the evolution of life histories along a slow-fast continuum. Hibernation allows a diverse range of small mammals to exhibit seasonal dormancy, which might increase survival and consequently be associated with relatively slow life histories. We used phylogenetically informed GLS models to test for an effect of hibernation on seasonal and annual survival, and on key attributes of life histories among mammals. Monthly survival was in most cases higher during hibernation compared with the active season, probably because inactivity minimizes predation. Hibernators also have approximately 15 per cent higher annual survival than similar sized non-hibernating species. As predicted, we found an effect of hibernation on the relationships between life history attributes and body mass: small hibernating mammals generally have longer maximum life spans (50% greater for a 50 g species), reproduce at slower rates, mature at older ages and have longer generation times compared with similar-sized non-hibernators. In accordance with evolutionary theories, however, hibernating species do not have longer life spans than non-hibernators with similar survival rates, nor do they have lower reproductive rates than non-hibernators with similar maximum life spans. Thus, our combined results suggest that (i) hibernation is associated with high rates of overwinter and annual survival, and (ii) an increase in survival in hibernating species is linked with the coevolution of traits indicative of relatively slow life histories

A magnetic resonance functional neuroimaging study of cortical regions associated with motor tasl execution and motor ideation in humans

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