Over the past decades nonulosonic acids have been increasingly found in (pathogenic) prokaryotes, decorating the contact surface to their external environments. A recent phylogenetic large-scale study, covering nearly 1,000 microbial genomes, discovered a surprisingly wide distribution of an ancient core nonulosonic acid biosynthetic pathway, which was shown to be widely spread amongst both bacteria and archaea. However, predicted ORFs often do not encode for functional entities, and most importantly, genomics alone does not reveal the important post synthesis processing events, which make nonulosonic acids so unique.
Here, we provide a first large-scale comparative study and molecular signature of the broad diversity of nonulosonic acids, by surveying a large number of species throughout the phylogenetic tree of life, using high-resolution mass spectrometry. We established a fully open, but nonulosonic acid specific approach (called all ion reaction monitoring, AIRM), capable of differentiating between different classes of nonulosonic acids, as well as species-specific post synthesis processing events. Furthermore, the high specificity of the assay allows to directly analyse from crude cell lysates.
This study illustrates not only the common utilisation of nonulosonic acids between various species but also gives insight into species specific post-synthesis processes. Though the significance of bacterial sialic acids in host/pathogen interactions has been established over the past decades, our study aims to provide further evidence for their wide-spread utilisation in environmental species.
- There are many open questions surrounding the evolution and utilisation of nonulosonic acids in prokaryotes. Unfortunately, the analysis with conventional methods is a laborious process. We developed therefore a fast but highly specific assay for the discovery of novel nonulosonic acid variants.
- We provide a comparative large-scale study on the molecular level demonstrating the diversity and distribution of different classes of nonulosonic acids across species, including purely environmental samples;
- The developed assay serves as a tool to explore complex samples and communities to study the broader ecological context of this prominent, but still poorly analysed class of sugars.