Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

• Published in: Antimicrobial agents and chemotherapy 2015-10, Vol.59 (10), p.6352-6360
• Main Authors: Kurabayashi, Kumiko, Tanimoto, Koichi, Fueki, Shinobu, Tomita, Haruyoshi, Hirakawa, Hidetada
• Format: Article
• Language: English
• Subjects: Anaerobiosis; Anti-Bacterial Agents; Anti-Bacterial Agents - metabolism; Anti-Bacterial Agents - pharmacology; Binding Sites; Biological Transport; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Fosfomycin; Fosfomycin - metabolism; Fosfomycin - pharmacology; Gene Expression Regulation, Bacterial; Glucose-6-Phosphate - metabolism; Glycerophosphates - metabolism; Iron-Sulfur Proteins; Iron-Sulfur Proteins - genetics; Iron-Sulfur Proteins - metabolism; Mechanisms of Action: Physiological Effects; Membrane Transport Proteins; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Monosaccharide Transport Proteins; Monosaccharide Transport Proteins - genetics; Monosaccharide Transport Proteins - metabolism; Promoter Regions, Genetic; Protein Binding; Recombinant Proteins - genetics; Recombinant Proteins - metabolism
• ISSN: 0066-4804; 1098-6596
• DOI: 10.1128/aac.01176-15

Because a shortage of new antimicrobial agents is a critical issue at present, and with the spread of multidrug-resistant (MDR) pathogens, the use of fosfomycin to treat infections is being revisited as a "last-resort option." This drug offers a particular benefit in that it is more effective against bacteria growing under oxygen-limited conditions, unlike other commonly used antimicrobials, such as fluoroquinolones and aminoglycosides. In this study, we showed that Escherichia coli strains, including enterohemorrhagic E. coli (EHEC), were more susceptible to fosfomycin when grown anaerobically than when grown aerobically, and we investigated how the activity of this drug was enhanced during anaerobic growth of E. coli. Our quantitative PCR analysis and a transport assay showed that E. coli cells grown under anaerobic conditions had higher levels of expression of glpT and uhpT, encoding proteins that transport fosfomycin into cells with their native substrates, i.e., glycerol-3-phosphate and glucose-6-phosphate, and led to increased intracellular accumulation of the drug. Elevation of expression of these genes during anaerobic growth requires FNR, a global transcriptional regulator that is activated under anaerobic conditions. Purified FNR bound to DNA fragments from regions upstream of glpT and uhpT, suggesting that it is an activator of expression of glpT and uhpT during anaerobic growth. We concluded that the increased antibacterial activity of fosfomycin toward E. coli under anaerobic conditions can be attributed to elevated expression of GlpT and UhpT following activation of FNR, leading to increased uptake of the drug.