Phylogenetic distance and structural diversity directing a reclassification of glycopeptide antibiotics

Antibiotics have been an essential part of modern medicine since their initial discovery. The continuous search for new antibiotic candidates remains a necessity given the increasing emergence of resistance to antimicrobial compounds among pathogens. The glycopeptide antibiotics (GPAs) represent an important group of last resort antibiotics which inhibit bacterial growth through non-covalent binding to the cell wall precursor lipid II. The so far reported GPAs exhibit an enormous diversity in the biosynthetic gene clusters that encode their production, which is in turn reflected in the variety of their structures. GPAs are typically composed of seven amino acids, which are highly crosslinked and decorated with a variable collection of sugar moieties as well as other modifications. Based on their structural characteristics, they have been classified into four main types. More recently, atypical GPAs have been identified that differ from type I-IV GPAs in both their structure and function and have consequently been classified as type V GPAs. Given these differences, we studied the phylogeny of all gene sequences related to the biosynthesis of the GPAs and observed a clear evolutionary diversification between the lipid II binding GPA classes and the so-called type V GPAs. Here we suggest the adoption of a phylogeny-driven reclassification and a separation of classical lipid II binding GPAs from type V GPAs, which we propose to identify instead as glycopeptide- related peptides (GRPs).