Evolution of antibiotic resistance in microbes is frequently achieved by acquisition of spontaneous mutations during antimicrobial therapy. Here we demonstrate that inactivation of a central regulator of iron homeostasis (fur) facilitates laboratory evolution of ciprofloxacin resistance in Escherichia coli. To decipher the underlying molecular mechanisms, we first performed a global transcriptome analysis and demonstrated a substantial reorganization of the Fur regulon in response to antibiotic treatment. We hypothesized that the impact of Fur on evolvability under antibiotic pressure is due to the elevated intracellular concentration of free iron and the consequent enhancement of oxidative damage-induced mutagenesis. In agreement with expectations, over-expression of iron storage proteins, inhibition of iron transport, or anaerobic conditions drastically suppressed the evolution of resistance, while inhibition of the SOS response-mediated mutagenesis had no such effect in fur deficient population. In sum, our work revealed the central role of iron metabolism in de novo evolution of antibiotic resistance, a pattern that could influence the development of novel antimicrobial strategies.
Perturbation of iron homeostasis promotes the evolution of antibiotic resistance.
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View SamplesThe purpose of this experiment was to identify oestrogen regulated genes in human primary cell cultures of neuronal and glial cells modelling the developing human nervous system. We were especially interested in genes involved in proliferation, differentiation and migration of neuronal cells and genes involved in or linked to neurodegenerative diseases. We have therefore assessed gene expression changes, using Affymetrix GeneChips (HG-U133A), of oestrogen treated human neuronal/ glial cell cultures. We continued with 14 selected genes and confirmed the gene expression changes, by relative quantitative real time PCR, of 6 genes (p< 0.05) important in neuronal development, three of which also are suggested to have links to neurodegenerative diseases.
Transcriptional analysis of estrogen effects in human embryonic neurons and glial cells.
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