Hernandez-Garcia, J. | bioRxiv Science

bioRxiv2018

One Health genomic surveillance of Escherichia coli demonstrates distinct lineages and mobile genetic elements in isolates from humans versus livestock

Livestock have been proposed as a reservoir for drug-resistant Escherichia coli that infect humans. We isolated and sequenced 431 E. coli (including 155 ESBL-producing isolates) from cross-sectional surveys of livestock farms and retail meat in the East of England. These were compared with the genomes of 1517 E. coli associated with bloodstream infection in the United Kingdom. Phylogenetic core genome comparisons demonstrated that livestock and patient isolates were genetically distinct, indicating that E. coli causing serious human infection do not directly originate from livestock. By contrast, we observed highly related isolates from the same animal species on different farms. Analysis of accessory (variable) genomes identified a virulence cassette associated previously with cystitis and neonatal meningitis that was only present in isolates from humans. Screening all 1948 isolates for accessory genes encoding antibiotic resistance revealed 41 different genes present in variable proportions of humans and livestock isolates. We identified a low prevalence of shared antimicrobial resistance genes between livestock and humans based on analysis of mobile genetic elements and long-read sequencing. We conclude that in this setting, there was limited evidence to support the suggestion that antimicrobial resistant pathogens that cause serious infection in humans originate from livestock.\n\nImportanceThe increasing prevalence of E. coli bloodstream infections is a serious public health problem. We used genomic epidemiology in a One Health study conducted in the East of England to examine putative sources of E. coli associated with serious human disease. E. coli from 1517 patients with bloodstream infection were compared with 431 isolates from livestock farms and meat. Livestock-associated and bloodstream isolates were genetically distinct populations based on core genome and accessory genome analyses. Identical antimicrobial resistance genes were found in livestock and human isolates, but there was little overlap in the mobile elements carrying these genes. In addition, a virulence cassette found in humans isolates was not identified in any livestock-associated isolate. Our findings do not support the idea that E. coli causing invasive disease or their resistance genes are commonly acquired from livestock.

genomics↗

bioRxiv2018

Origin of gibberellin-dependent transcriptional regulation by molecular exploitation of a transactivation domain in DELLA proteins

DELLA proteins are land-plant specific transcriptional regulators known to interact through their C-terminal GRAS domain with over 150 transcription factors in Arabidopsis thaliana. Besides, DELLAs from vascular plants can interact through the N-terminal domain with the gibberellin receptor encoded by GID1, through which gibberellins promote DELLA degradation. However, this regulation is absent in non-vascular land plants, which lack active gibberellins or a proper GID1 receptor. Current knowledge indicates that DELLAs are important pieces of the signalling machinery of vascular plants, especially angiosperms, but nothing is known about DELLA function during early land plant evolution or if they exist at all in charophytan algae. We have now elucidated the evolutionary origin of DELLA proteins, showing that algal GRAS proteins are monophyletic and evolved independently from those of land plants, which explains why there are no DELLAs outside land plants. DELLA genes have been maintained throughout land plant evolution with only two major duplication events kept among plants. Furthermore, we show that the features needed for DELLA interaction with the receptor were already present in the ancestor of all land plants, and propose that these DELLA N-terminal motifs have been tightly conserved in non-vascular land plants for their function in transcriptional co-activation, which allowed subsequent exaptation for the interaction with the GID1 receptor when vascular plants developed gibberellin synthesis and the corresponding perception module.

evolutionary biology↗