It is generally accepted that resistance genes acquired by human pathogens through horizontal gene transfer originated in environmental, non-pathogenic bacteria. As a consequence, there is increasing concern on the roles that natural, non-clinical ecosystems, may play in the evolution of resistance. Recent studies have shown that the variability of determinants that can provide antibiotic resis...

Streptococcus mutans strains were isolated from cohorts of Brazilian nursery school children and genotyped by arbitrarily primed PCR and restriction fragment length polymorphism analysis. Of 24 children with two to five S. mutans isolates, 29% carried two or more genotypes. The presence of matching genotypes of S. mutans among children attending one nursery suggests horizontal transmission.

The three relevant solutions of these equations are (i) (N T , N ∗ A) = (0, 0): this is the trivial case where both populations are zero. (ii) (N T , N ∗ A) = (K, 0): this solution describes a domain full with individuals that do not carry the trait; no trait-carrying individuals are present. (iii) (N T , N ∗ A) = (K,K − β/γ): this solution is the most interesting one for our purposes. It descr...

Horizontal gene transfer (HGT) is the movement of genetic information between organisms, a process that includes the spread of antibiotic resistance genes among bacteria (except for those from parent to offspring), fueling pathogen evolution. Many resistance genes evolved long ago in natural environments with no anthropogenic influence but these genes are now rapidly spreading to and among huma...

Boriana K. Tchernookova, Ethan R. Naylor, 4 Robert Paul Malchow 5 6 1 Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA 7 2 Department of Biology, Indiana Wesleyan University, Marion, IN, USA 8 3 National Eye Institute, Bethesda, MD, USA 9 4 Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 10 Chicago, IL, USA 11 12

Effects of a model for random bottom structure on acoustic intensity in isospeed shallow water are studied. The randomness is due to stochastic variations in the bottom density and sound speed in the horizontal direction beneath a plane water-bottom interface. Ray geometry, spreading loss, and bottom loss and phase shift are examined in order to derive formulas for mean intensity and the varian...

OBJECTIVES The aim of this study was to determine the occurrence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli at an equine clinic and a horseback riding centre, and to discuss the impact of antimicrobial treatment on resistance selection. METHODS Faeces from horses, environmental smears and flies were sampled at both the clinic and riding centre. Staff at the equine clin...

Douglas Theobald recently developed an interesting test putatively capable of quantifying the evidence for a Universal Common Ancestry uniting the three domains of life (Eukarya, Archaea and Bacteria) against hypotheses of Independent Origins for some of these domains. We review here his model, in particular in relation to the treatment of Horizontal Gene Transfer (HGT) and to the quality of se...

Many insect species maintain mutualistic relationships with endosymbiotic bacteria. In contrast to their free-living relatives, horizontal gene transfer (HGT) has traditionally been considered rare in long-term endosymbionts. Nevertheless, meta-omics exploration of certain symbiotic models has unveiled an increasing number of bacteria-bacteria and bacteria-host genetic transfers. The abundance ...

Biological systems are modular, and this modularity affects the evolution of biological systems over time and in different environments. We here develop a theory for the dynamics of evolution in a rugged, modular fitness landscape. We show analytically how horizontal gene transfer couples to the modularity in the system and leads to more rapid rates of evolution at short times. The model, in ge...