Horizontal gene transfer (HGT) can allow traits that have evolved in one bacterial species to transfer to another. This has potential to rapidly promote new adaptive trajectories such as zoonotic ...transfer or antimicrobial resistance. However, for this to occur requires gaps to align in barriers to recombination within a given time frame. Chief among these barriers is the physical separation of species with distinct ecologies in separate niches. Within the genus
there are species with divergent ecologies, from rarely isolated single-host specialists to multihost generalist species that are among the most common global causes of human bacterial gastroenteritis. Here, by characterizing these contrasting ecologies, we can quantify HGT among sympatric and allopatric species in natural populations. Analyzing recipient and donor population ancestry among genomes from 30
species, we show that cohabitation in the same host can lead to a six-fold increase in HGT between species. This accounts for up to 30% of all SNPs within a given species and identifies highly recombinogenic genes with functions including host adaptation and antimicrobial resistance. As described in some animal and plant species, ecological factors are a major evolutionary force for speciation in bacteria and changes to the host landscape can promote partial convergence of distinct species through HGT.
A research report submitted to the Faculty of Health Sciences, University of the;
Witwatersrand, in partial fulfilment of the requirements for the degree;
of;
Master of Science in Medicine in ...Emergency Medicine.;
Johannesburg, 2015
Aim: To determine any association between the lunar synodic or anomalistic;
months and the nature and volume of emergency department patient consultations;
and hospital admissions from the emergency department (ED).;
Design: A retrospective, descriptive study.;
Setting: All South African EDs of a private hospital group.;
Patients: All patients consulted from 01 January 2005 to 31 December 2010.;
Methods: Data was extracted from monthly records and statistically evaluated,;
controlling for calendric variables. Lunar variables were modelled with volumes of;
differing priority of hospital admissions and consultation categories including;;
trauma, medical, paediatric, work injuries, obstetrics and gynaecology, intentional;
self harm, sexual assault, dog bites and total ED consultations.;
Main Results: No significant differences were found in all anomalistic and most;
synodic models with the consultation categories. Small but significant increases;
were found with a small number of synodic models around full moon with some;
categories, P2 medical, total paediatric consultations and total admissions.;
Significant decreases in admissions, particulary total admissions, were found;
around perigee. The effect sizes of all significant lunar associations were smaller;
than those of the calendric variables.;
Conclusions: Most comparisons demonstrated no lunar association. Small but;
significant associations were demonstrated around full moon with some synodic;
models. A number of anomalistic admission models demonstrated small but;
significant decreases in admissions at perigee.
The vaccinia virus DNA telomere, which contains a covalently closed hairpin structure, has been cloned in a yeast plasmid vector. Restriction mapping indicates that the cloned vaccinia telomere is ...maintained in yeast not in its native hairpin configuration but as an inverted repeat structure, within a circular plasmid, with the sequences of the viral hairpin now at the axis of symmetry of an imperfect palindrome. As such, the cloned telomere resembles the telomeric replicative intermediate observed during vaccinia virus DNA replication. Small deletions and duplications in the viral inverted repeats of different clones suggest a model in which the observed circular plasmids were generated in yeast by the replication of hybrid linear DNA molecules consisting of the linearized yeast vector flanked by two hairpin-containing vaccinia termini.
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