Copper inhibits peptidoglycan LD-transpeptidases suppressing β-lactam resistance due to bypass of penicillin-binding proteins

Abstract

The peptidoglycan (PG) layer stabilizes the bacterial cell envelope to maintain the integrity and shape of the cell. Penicillin-binding proteins (PBPs) synthesize essential 4–3 cross-links in PG and are inhibited by β-lactam antibiotics. Some clinical isolates and laboratory strains of Enterococcus faecium and Escherichia coli achieve high-level β-lactam resistance by utilizing β-lactam–insensitive LD-transpeptidases (LDTs) to produce exclusively 3–3 cross-links in PG, bypassing the PBPs. In E. coli, other LDTs covalently attach the lipoprotein Lpp to PG to stabilize the envelope and maintain the permeability barrier function of the outermembrane. Here we show that subminimal inhibitory concentration of copper chloride sensitizes E. coli cells to sodium dodecyl sulfate and impair survival upon LPS transport stress, indicating reduced cell envelope robustness. Cells grown in the presence of copper chloride lacked 3–3 cross-links in PG and displayed reduced covalent attachment of Braun’s lipoprotein and reduced incorporation of a fluorescent d-amino acid, suggesting inhibition of LDTs. Copper dramatically decreased the minimal inhibitory concentration of ampicillin in E. coli and E. faecium strains with a resistance mechanism relying on LDTs and inhibited purified LDTs at submillimolar concentrations. Hence, our work reveals how copper affects bacterial cell envelope stability and counteracts LDT-mediated β-lactam resistance.

A Fluorescence‐Based Assay for Screening β‐Lactams Targeting the Mycobacterium tuberculosis Transpeptidase LdtMt2

“…Addition of NaCl to the buffer decreased probe degradation, but had a negative impact on reaction rate and was therefore omitted from subsequent assays (Figure S4). As metal ions (i.e., Cu 2+ ) are thought to interact directly with Cys354 of Ldt Mt2 , sodium ions in the buffer might similarly slow reaction with probes 2 and 3 .…”

Environmental pH impacts division assembly and cell size inEscherichia coli

“…Although the underlying molecular mechanisms remain unclear, media osmolarity affects the growth of cells harboring conditional mutants of division genes, dictates essentiality of FtsEX for division, and modulates cell size in E. coli [44,73,74]. Extracellular metal availability also alters the activity of several nonessential cell wall enzymes [75–77]. Further exploration promises to illuminate additional environmental determinants modulating the activity of not only enzymes involved in bacterial cell wall synthesis, but also other extracytoplasmic processes.…”

A rugged, self-sterilizing antimicrobial copper coating on ultra-high molecular weight polyethylene: a preliminary study on the feasibility of an antimicrobial prosthetic joint material

“…10 Antimicrobial copper coatings on orthopaedic material like titanium and titanium alloy have also been reported by Wan et al 11 The alternative cycle of cupric and cuprous ions trigger an intracellular redox potential which can lead to instability and therefore cell damage. 12 In addition, 'Fenton type' chemistry in the presence of molecular oxygen following the production of superoxide and other reactive oxygen species can cause detrimental cellular damage to the bacteria. 12,13 Bacterial cell wall synthesis is carried out by enzymes known as DD-transpeptidases which are the target of b-lactams antibiotics such as penicillin.…”

“…12 In addition, 'Fenton type' chemistry in the presence of molecular oxygen following the production of superoxide and other reactive oxygen species can cause detrimental cellular damage to the bacteria. 12,13 Bacterial cell wall synthesis is carried out by enzymes known as DD-transpeptidases which are the target of b-lactams antibiotics such as penicillin. Some bacteria produce an alternative enzyme known as LD-transpeptidase which allows cell wall synthesis even in the presence of b-lactams and a recent study showed that copper ions can inhibit LD-transpeptidases thus rendering b-lactamresistant bacteria susceptible.…”

“…Some bacteria produce an alternative enzyme known as LD-transpeptidase which allows cell wall synthesis even in the presence of b-lactams and a recent study showed that copper ions can inhibit LD-transpeptidases thus rendering b-lactamresistant bacteria susceptible. 12 The intrinsically inert UHMWPE provides stable long-term performance in prosthetic applications, but this also means that the incorporation of antimicrobial agents is difficult. Following previous work on low temperature precursor conversion, 14,15 the key idea here was to introduce a selfreducing copper precursor, that can undergo pyrolysis at relatively low temperature to form copper containing particles onto a temperature sensitive polymer.…”