Bacterial cell wall-degrading enzymes induce basidiomycete natural product biosynthesis

Interspecific cross-talk: The catalyst driving microbial biosynthesis of secondary metabolites

Microorganisms co-exist and co-evolve in nature, forming intricate ecological communities. The interspecies cross-talk within these communities creates and sustains their great biosynthetic potential, making them an important source of natural medicines and high-value-added chemicals. However, conventional investigations into microbial metabolites are typically carried out in pure cultures, resulting in the absence of specific activating factors and consequently causing a substantial number of biosynthetic gene clusters to remain silent. This, in turn, hampers the in-depth exploration of microbial biosynthetic potential and frequently presents researchers with the challenge of rediscovering compounds. In response to this challenge, the coculture strategy has emerged to explore microbial biosynthetic capabilities and has shed light on the study of cross-talk mechanisms. These elucidated mechanisms will contribute to a better understanding of complex biosynthetic regulations and offer valuable insights to guide the mining of secondary metabolites. This review summarizes the research advances in microbial cross-talk mechanisms, with a particular focus on the mechanisms that activate the biosynthesis of secondary metabolites. Additionally, the instructive value of these mechanisms for developing strategies to activate biosynthetic pathways is discussed. Moreover, challenges and recommendations for conducting in-depth studies on the cross-talk mechanisms are presented.

Bifurcate evolution of quinone synthetases in basidiomycetes

BACKGROUND

The terphenylquinones represent an ecologically remarkable class of basidiomycete natural products as they serve as central precursors of pigments and compounds that impact on microbial consortia by modulating bacterial biofilms and motility. This study addressed the phylogenetic origin of the quinone synthetases that assemble the key terphenylquinones polyporic acid and atromentin.

RESULTS

The activity of the Hapalopilus rutilans synthetases HapA1, HapA2 and of Psilocybe cubensis PpaA1 were reconstituted in Aspergilli. Liquid chromatography and mass spectrometry of the culture extracts identified all three enzymes as polyporic acid synthetases. PpaA1 is unique in that it features a C-terminal, yet catalytically inactive dioxygenase domain. Combined with bioinformatics to reconstruct the phylogeny, our results demonstrate that basidiomycete polyporic acid and atromentin synthetases evolved independently, although they share an identical catalytic mechanism and release structurally very closely related products. A targeted amino acid replacement in the substrate binding pocket of the adenylation domains resulted in bifunctional synthetases producing both polyporic acid and atromentin.

CONCLUSIONS

Our results imply that quinone synthetases evolved twice independently in basidiomycetes, depending on the aromatic α-keto acid substrate. Furthermore, key amino acid residues for substrate specificity were identified and changed which led to a relaxed substrate profile. Therefore, our work lays the foundation for future targeted enzyme engineering.

Facing crises in the 21st century: microfluidics approaches for antibiotic discovery

We urgently need new antibiotics to counteract the rising in the emergence of multidrug-resistant microorganisms. To improve the identification of antimicrobial compounds of microbial origin, numerous multidisciplinary approaches are being implemented. However, the development of innovative microbial cultivation strategies is necessary to exploit the full biosynthetic potential of non-culturable microorganisms. Here, I highlight various articles that employ high-throughput microfluidic-based strategies to identify novel antimicrobial metabolites based on bacterial activities. The rapid development of this technology will likely advance the field of antibiotic discovery.