Samphire, J. | bioRxiv Science

bioRxiv2022

An Azobenzene G-quadruplex Ligand Exhibits Promising Antibacterial Activity against Escherichia coli

There is great need for novel strategies to tackle antimicrobial resistance, in particular in Gram-negative species such as Escherichia coli that cause opportunistic infections of already compromised patients. Here we demonstrate, following a screen of G-quadruplex (G4) ligand candidates, that a novel pyridinium-functionalized azobenzene L9 shows promising antibacterial activity (MIC values [≤] 4 g/mL) against multi-drug resistant E. coli. Tandem Mass Tag (TMT) proteomics of E. coli treated with sub-lethal concentrations of L9, identified that, consistent with its superior antibacterial activity, L9 treatment influences expression levels of more G4-associated proteins than the analogous ligands L5 (stiff-stilbene) or pyridostatin (PDS), and upregulates multiple essential proteins involved in translation. Biophysical analysis showed L9 binds potential target G4-containing sequences, identified from proteomic experiments and by bioinformatics, with variable affinity, in contrast to the two comparator G4 ligands (L5, PDS) that better stabilize G4 structures but have lower antimicrobial activity. Fluorescence microscopy-based Bacterial Cytological Profiling (BCP) suggests that the L9 mechanism of action is distinct from other antibiotic classes. These findings support strategies discovering potential G4 ligands as antibacterial candidates for priority targets such as multi-drug resistant E. coli, warranting their further exploration as potential novel therapeutic leads with G4-mediated modes of action. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/506212v2_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@18197a0org.highwire.dtl.DTLVardef@109b120org.highwire.dtl.DTLVardef@14be8eeorg.highwire.dtl.DTLVardef@a97048_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2021

Green Fluorescent Carbon Dots as Targeting Probes for LED-Dependent Bacterial Killing

The emergence of antimicrobial resistance represents a significant health and economic challenge worldwide. The slow pace of antibacterial discovery necessitates strategies for optimal use of existing agents, including effective diagnostics able to drive informed prescribing; and development of alternative therapeutic strategies that go beyond traditional small-molecule approaches. Thus, the development of novel probes able to target bacteria for detection and killing, and that can pave the way to effective theranostic strategies, is of great importance. Here we demonstrate that metal-free green-emitting fluorescent carbon dots (FCDs) synthesized from glucosamine HCl and m-phenylenediamine, and featuring 2,5-deoxyfructosazine on a robust amorphous core, can label both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) bacterial pathogens within 10 minutes of exposure. Moreover, effective killing of Gram-positive and -negative bacteria can be induced by combining FCD treatment with irradiation by LED light in the visible range. Cell-based, electron microscopy and Tandem Mass Tag (TMT) proteomic experiments indicate that FCD administration in combination with LED exposure gives rise to local heating, ROS production, and membrane- and DNA-damage, suggesting multiple routes to FCD-mediated bacterial killing. Our data identify FCDs as materials that combine facile synthesis from low-cost precursors with labelling and light-dependent killing of clinically important bacterial species, and that thus warrant further exploration as the potential bases for novel theranostics.

microbiology↗