Biology subjects

Evangelopoulos, D.

Publications and source records attributed to Evangelopoulos, D..

3 recordsLinked to original sources

bioRxiv2018

Antibiotic resistance evasion is explained by rare mutation frequency and not by lack of compensatory mechanisms

Drug resistant infections represent one of the most challenging medical problems of our time. D-cycloserine is an antibiotic used for decades without appearance and dissemination of antibiotic resistant strains, making it an ideal model compound to understand what drives resistance evasion. We investigated why Mycobacterium tuberculosis fails to become resistant to D-cycloserine. To address this question we employed a combination of bacterial genetics, genomics, biochemistry and fitness analysis in vitro, in macrophages and in mice. Altogether, our results suggest that the ultra-low mutation frequency associated with D-cycloserine resistance is the dominant factor delaying the appearance of clinical resistance to this antibiotic in bacteria infecting humans, and not lack of potential compensatory mechanisms.\n\nOne Sentence SummaryWe show that the lack of D-cycloserine resistance in Mycobacterium tuberculosis is due its ultra-low mutation frequency rather than lack of compensatory mechanisms.

microbiology↗

bioRxiv2018

A role for a conserved kinase in the transcriptional control of methionine biosynthesis in Escherichia coli experiencing sustained nitrogen starvation

The initial adaptive transcriptional response to nitrogen (N) starvation in Escherichia coli involves large-scale alterations to the transcriptome mediated by the transcription activator, NtrC. One of the NtrC-activated genes is yeaG, which encodes a conserved bacterial kinase. Although it is known that YeaG is required for optimal survival under sustained N starvation, the molecular basis by which YeaG benefits N starved E. coli remains elusive. By combining transcriptomics with targeted metabolomics analyses, we demonstrate that the methionine biosynthesis pathway becomes transcriptionally dysregulated in{Delta} yeaG bacteria experiencing sustained N starvation. This results in the aberrant and energetically costly biosynthesis of methionine and associated metabolites under sustained N starvation with detrimental consequences to cell viability. It appears the activity of the master transcriptional repressor of methionine biosynthesis genes, MetJ, is compromised in{Delta} yeaG bacteria under sustained N starvation, resulting in transcriptional derepression of MetJ-regulated genes. The results suggest that YeaG is a novel regulatory factor and functions as a molecular brake in the transcriptional control of both the NtrC-regulon and methionine biosynthesis genes in E. coli experiencing sustained N starvation.

microbiology↗

bioRxiv2017

Polymersomes Targeting Mononuclear Phagocytes

Mononuclear phagocytes such as monocytes, tissue-specific macrophages and dendritic cells are primary actors in both innate and adaptive immunity, as well as tissue homoeostasis. They have key roles in a range of physiological and pathological processes, so any strategy targeting these cells will have wide-ranging impact. These phagocytes can be parasitized by intracellular bacteria, turning them from housekeepers to hiding places and favouring chronic and/or disseminated infection. One of the most infamous is the bacteria that cause tuberculosis, which is the most pandemic and one of the deadliest disease with one third of the worlds population infected, and 1.8 million deaths worldwide in 2015. Here we demonstrate the effective targeting and intracellular delivery of antibiotics to both circulating monocytes and resident macrophages, using pH sensitive nanoscopic polymersomes made of poly(2-(methacryloyloxy)ethyl phosphorylcholine)-co-poly(2-(di-isopropylamino)ethyl methacrylate) (PMPC-PDPA). Polymersome selectivity to mononuclear phagocytes is demonstrated and ascribed to the polymerised phosphorylcholine motifs affinity toward scavenger receptors. Finally, we demonstrate the successful exploitation of this targeting for the effective eradication of intracellular bacteria that cause tuberculosis Mycobacterium tuberculosis as well as other intracellular parasites including the Mycobacterium bovis, Mycobacterium marinum and the most common bacteria associated with antibiotic resistance, the Staphylococcus aureus.

immunology↗