Investigating the ecological context of microbial predator−prey interactions enables the identification of microorganisms, which produce multiple secondary metabolites to evade predation or to kill the predator. In addition, genome mining combined with molecular biology methods can be used to identify further biosynthetic gene clusters that yield new antimicrobials to fight the antimicrobial crisis. In contrast, classical screening-based approaches have limitations since they do not aim to unlock the entire biosynthetic potential of a given organism. Here, we describe the genomics-based identification of keanumycins A−C. These nonribosomal peptides enable bacteria of the genus Pseudomonas to evade amoebal predation. While being amoebicidal at a nanomolar level, these compounds also exhibit a strong antimycotic activity in particular against the devastating plant pathogen Botrytis cinerea and they drastically inhibit the infection of Hydrangea macrophylla leaves using only supernatants of Pseudomonas cultures. The structures of the keanumycins were fully elucidated through a combination of nuclear magnetic resonance, tandem mass spectrometry, and degradation experiments revealing an unprecedented terminal imine motif in keanumycin C extending the family of nonribosomal amino acids by a highly reactive building block. In addition, chemical synthesis unveiled the absolute configuration of the unusual dihydroxylated fatty acid of keanumycin A, which has not yet been reported for this lipodepsipeptide class. Finally, a detailed genome-wide microarray analysis of Candida albicans exposed to keanumycin A shed light on the mode-of-action of this potential natural product lead, which will aid the development of new pharmaceutical and agrochemical antifungals.
Cyclic lipopeptides are substances with a high potential to act as antimicrobial agents. Jagaricin, produced by Janthinobacterium agaricidamnosum DSM 9628 and discovered in 2012, is a new member of this class with promising antifungal properties. However, further experiments to investigate future applications and/or conduct chemical derivatization to change properties and toxicity are impossible due to the limited access to jagaricin. Besides a high jagaricin concentration at the end of the fermentation process, a suitable downstream process is essential to generate appropriate amounts with the desired purity. In contrast to other amphiphilic molecules, jagaricin cannot be separated by foam fractionation since it is mainly attached to the surface of the microbial biomass. This technical report presents an overall process chain consisting of 11 individual steps to generate jagaricin in gram scale with a purity of over 95%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.