We have successfully developed the proposed method for fatty acid-incorporating metabolite discovery and have found several new natural products from only a couple of cyanobacteria. Some of these compounds are structurally unique, highlighting the potential of cyanobacteria for the discovery of novel natural products (Figueiredo et al. 2021).
Furthermore, we have studied the biosynthesis of the bartolosides and revealed a biocatalytic transformation, mediated by the enzyme BrtB, which was until then only known in synthetic chemistry. This enzymatic reaction is a new type of biological esterification in which the fatty acids are esterified to a halogenated carbon. Most strikingly, the fatty acids react as free carboxylates and therefore bypass what was thought was a universal requirement: fatty acid activation (Reis et al 2020).
We have critically reviewed the literature on the alkylresorcinol-type of fatty acid-incorporating metabolites. We looked into the entire diversity of these compounds in cyanobacteria and identified opportunities for discovery of new metabolites and enzymes (Martins et al 2019).
We disclosed the first natural biosynthetic pathway involved in the production of natural lactylates, which we envision will enable future biological production and engineering of industrially-relevant lactylates (Abt et al 2021).
We also showed the initial steps in the biosynthesis of the unusual natural product Noculin A, as well as the origin of all its carbon atoms, paving the way for uncovering key steps in the biosynthesis of its unique 1,2,3-oxadiazine core (Martins et al 2022).
With what we have learned during the course of the project, we summarised current knowledge on the incorporation, fate and turnover of free fatty acids in cyanobacteria in general, and also in the specific case of secondary metabolites with associated modifications of their alkyl chains, in two peer-reviewed publications (Kahn et al, 2023 and Leao et al, 2023).
Yet to be published, we have discovered the highly intriguing lipopeptides fischerazoles and that their biosynthesis involves an unprecedented mid-alkyl chain carbon rearrangement (Figueiredo et al, 2022 - preprint). We have also implicated NocC - an enzyme encoded in the nocuolactylates biosynthetic gene cluster - in the generation of beta, gamma-unsaturations in fatty acyl moieties. We have additionally further studied the biosynthesis of nocuolin A and uncovered the role of several enzymes in this pathway, in particular those of a C-oxygenase and an unusual aminotranferase that appears to generate an imino group of a ketone.
All of these findings have been communicated to scientific peers and stundents, in conferences and invited seminars.
The new method developed (Figueiredo et al 2021) and the discovery of the activity of BrtB (Reis et al 2020) were the subject of press releases and featured in news outlets of national (PT) reach.
Several MSc students, PhD students and postdocs were trained in multidisciplinary natural products research during the course of the project, which was also a major achievement of FattyCyanos.
