Abstract
Vancomycin is a front-line antibiotic used for the treatment of nosocomial infections, particularly those caused by methicillin-resistant Staphylococcus aureus. Despite its clinical importance the global effects of vancomycin exposure on bacterial physiology are poorly understood. In a previous transcriptomic analysis we identified a number of Zur regulon genes which were highly but transiently up-regulated by vancomycin in Streptomyces coelicolor. Here, we show that vancomycin also induces similar zinc homeostasis systems in a range of other bacteria and demonstrate that vancomycin binds to Zn(II) in vitro. This implies that vancomycin treatment sequesters zinc from bacterial cells thereby triggering a Zur-dependent zinc starvation response. The Kd value of the binding between vancomycin and Zn(II) was calculated using a novel fluorometric assay, and NMR was used to identify the binding site. These findings highlight a new biologically relevant aspect of the chemical property of vancomycin as a zinc chelator.
Highlights
The glycopeptide antibiotic vancomycin was first discovered in the 1950’s1
To investigate the ability of vancomycin to induce a zinc starvation response in different species of bacteria, cultures of S. coelicolor, Streptomyces griseus, Streptomyces roseosporus, Escherichia coli and Bacillus subtilis were treated with vancomycin for 30 min and changes in transcription of Zur-regulated genes quantified using qRT-PCR (Fig. 2)
Three putative Zur-regulated genes identified by bioinformatics analysis in two additional Streptomyces strains, S. griseus and S. roseosporus, showed a similar pattern of induction indicative of zinc starvation in response to vancomycin in these species (Fig. 2b,c)
Summary
The glycopeptide antibiotic vancomycin was first discovered in the 1950’s1. Since that time it has been reserved as an antibiotic of last resort for the treatment of multiple drug-resistant Gram-positive infectious agents, those resistant to β -lactam family antibiotics such as methicillin-resistant Staphylococcus aureus. We have previously undertaken an extensive transcriptome profiling study analyzing the effect of sub-inhibitory concentrations of three antibiotics, vancomycin, bacitracin and moenomycin A, that target distinctly different stages of cell wall biosynthesis in Streptomyces coelicolor[5] This model actinomycete is non-pathogenic and does not synthesize any glycopeptide antibiotic but possesses an inducible vancomycin resistance cluster that serves as a useful model for mechanistic investigations into high-level vancomycin resistance[6,7,8,9]. The simplest explanation for the observation that vancomycin treatment causes a zinc depletion response in S. ceolicolor cells is that the antibiotic directly chelates Zn(II), analogous to its known interaction with Cu(II)[14] This raises the possibility that zinc homeostasis is important for adaptation to antibiotic therapy in addition to host colonization. We determine the binding affinity of vancomycin for Zn(II) and define a potential binding site
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