Plasmid- and strain-specific factors drive variation in ESBL-plasmid spread in vitro and in vivo

Horizontal gene transfer, mediated by conjugative plasmids, is a major driver of the global rise of antibiotic resistance. However, the relative contributions of factors that underlie the spread of plasmids and their roles in conjugation in vivo are unclear. To address this, we investigated the spread of clinical Extended Spectrum Beta-Lactamase (ESBL)-producing plasmids in the absence of antibiotics in vitro and in the mouse intestine. We hypothesised that plasmid properties would be the primary determinants of plasmid spread and that bacterial strain identity would also contribute. We found clinical Escherichia coli strains natively associated with ESBL-plasmids conjugated to three distinct E. coli strains and one Salmonella enterica serovar Typhimurium strain. Final transconjugant frequencies varied across plasmid, donor, and recipient combinations, with qualitative consistency when comparing transfer in vitro and in vivo in mice. In both environments, transconjugant frequencies for these natural strains and plasmids covaried with the presence/absence of transfer genes on ESBL-plasmids and were affected by plasmid incompatibility. By moving ESBL-plasmids out of their native hosts, we showed that donor and recipient strains also modulated transconjugant frequencies. This suggests that plasmid spread in the complex gut environment of animals and humans can be predicted based on in vitro testing and genetic data.Subject terms: Antibiotics, Microbial ecology, Phylogenomics     

Exploring the low photosynthetic efficiency of cyanobacteria in blue light using a mutant lacking phycobilisomes

Photosynthesis Research - The ubiquitous chlorophyll a (Chl a) pigment absorbs both blue and red light. Yet, in contrast to green algae and higher plants, most cyanobacteria have much lower...     

Microchromatography of hemoglobins : VII. Detection of some uncommon hemoglobin variants and two rapid methods for the quantitation of Hb-A2 in the presence of Hb-C

Microchromatographic procedures on columns of DEAE- or CM-cellulose are described for the separation of the more common abnormal hemoglobins S and C from other, often uncommon, variants such as J, N, I, K-Woolwich, Hope, D, E, O, and Deer Lodge. Two procedures on conventionally sized columns of CM-cellulose permit the quantitative determination of Hb-A₂ in the presence of Hb-C in a day.     

Separation of the A gamma and G gamma cyanogen bromide peptides of human fetal hemoglobin by high-pressure liquid chromatography.

The ^Gγ and ^Aγ variants of human fetal hemoglobin are defined on the basis of a single glycine/alanine substitution at position 136 of the γ chain which is located in the carboxyterminal cyanogen bromide fragment (γCB-3). This communication describes the rapid separation of these two tridecapeptides by high-pressure liquid chromatography. Application of this new technique will facilitate the study of the biosynthesis and genetics of human fetal hemoglobin.