New peptide antibiotics stop bacteria by binding where the drug has not previously held

the study

Researchers produced a collection of environmental bacterial strains by culturing them in the laboratory for about a year. Such long-term cultures allow for the growth of the slowest growing bacteria that may otherwise have been overlooked.

They prepared methanol extracts of individual bacterial colonies and tested them against multidrug resistant bacteria. This identified a novel lassopeptide, lariosidin. Paenibacillus.

By conducting a series of biochemical and structural experiments, we discovered that lariosidin can kill a wide range of bacteria, including multidrug-resistant strains, by inhibiting ribosomal protein synthesis.

They also found that lariosidin binds to a unique site in the small ribosomal subunit of bacteria. This is clearly different from the site of action of existing antibiotics targeting small ribosomal subunits. This unique binding site allowed lariosidin to circumvent the defensive mechanisms that bacteria evolved to resist other drugs.

This ribosomal binding mode is primarily dependent on interaction with the RNA backbone rather than the nucleobase, making it less susceptible to resistance from mutations at the binding site.

In laboratory-adapted bacterial strains equipped with a single ribosomal RNA operon, the researchers identified rare spontaneous mutations in 16S RRNA that reduce lariosidin sensitivity.

The team emphasized that the development of antibiotics acting at previously undeveloped ribosomal sites provides a way to bypass common resistance mechanisms.

As the researchers observed, the unique structure of lariosidin has allowed them to overcome the challenges they normally face when targeting bacterial ribosomes. Mechanically, antibiotics enter bacterial cells through transporters to inhibit protein synthesis, particularly ribosomes. However, bacteria can replace or remove these transporters and block antibiotic invasion.

Meanwhile, the strong positive charge of lariosidin allowed it to enter bacterial cells directly through the membrane without the need for transporters. This particular feature has made lariosidin a wide range of antibiotics.

Lariosidin bypasses the need for specific transporters, thus allowing it to enter a wide range of bacterial species, reducing the likelihood that resistance will develop through transporter-related mechanisms.

Use the mouse model of acinetobacter baumannii Infection, researchers have demonstrated that lariosidin can significantly reduce the burden on bacteria in various organs. They further found that peptides are less likely to produce natural resistance and have no cytotoxic effects on human cells.

Its antibacterial activity was even stronger in nutrient restricted media that mimics the host environment, improving clinical potential compared to standard susceptibility tests of rich media.

This enhanced potency is in part related to the presence of bicarbonates, increasing the bacterial membrane potential and promoting the uptake of positively charged lariosidin.

All of these features have made lariosidin a promising candidate for further development into clinical antibiotics for the treatment of severe bacterial multidrug-resistant infections.

This study also identified a structurally related isoform, lariosidin B (LAR-B). This contained additional isopeptide bonds and formed a bilayer structure. This could improve the stability of molecules and mark LAR-B as founders of the proposed new class of lassopeptides (Class V).

By conducting bioinformatic analysis of available bacterial genomes, the researchers suggested that other ribosome-targeted lassopeptides could still be discovered in nature.

They identified dozens of lariosidin-like biosynthetic gene clusters (BGCs) across multiple bacterial phylums, including actinomycetota, blue bacilliota, and proteobacteria, suggesting a broad evolutionary distribution of this antibiotic scaffold.

Researchers describe lariosidin as the first member of the previously unrecognized ribosomal target lassopeptide, and it is possible that a more potent analogue could be discovered.

Researchers are currently working on developing strategies to modify lassopeptides and generate them in large quantities for clinical development.