Abstract
Our previous research has demonstrated a promising capacity of streptomycetes isolated from red soils to produce novel secondary metabolites, most of which, however, remain to be explored. Co-culturing with mycolic acid-containing bacteria (MACB) has been used successfully in activating the secondary metabolism in Streptomyces. Here, we co-cultured 44 strains of red soil-derived streptomycetes with four MACB of different species in a pairwise manner and analyzed the secondary metabolites. The results revealed that each of the MACB strains induced changes in the metabolite profiles of 35–40 streptomycetes tested, of which 12–14 streptomycetes produced “new” metabolites that were not detected in the pure cultures. Moreover, some of the co-cultures showed additional or enhanced antimicrobial activity compared to the pure cultures, indicating that co-culture may activate the production of bioactive compounds. From the co-culture-induced metabolites, we identified 49 putative new compounds. Taking the co-culture of Streptomyces sp. FXJ1.264 and Mycobacterium sp. HX09-1 as a case, we further explored the underlying mechanism of co-culture activation and found that it most likely relied on direct physical contact between the two living bacteria. Overall, our results verify co-culture with MACB as an effective approach to discover novel natural products from red soil-derived streptomycetes.
Highlights
The numbers represent aforementioned categories: increase/decrease, the yields of original metabolites produced in pure cultures increased/dethe number of streptomycetes or co-culture pairs. (a–d) Summarization of the effects of co-culture creased in the co-cultures; new, “new” metabolites with unique retention timeEach and/orHPLC
UV absorption exclusively appeared in the co-cultures; loss, original purecategories: culture me- infor each profilethat was classified according to the aforementioned tabolites lost in the co-cultures; and no change, no difference in secondary metabolite (SM) profiles was detected between the co-cultures and crease/decrease, the yields of original metabolites produced in pure cultures increased/decreased in pure cultures
To explore the cryptic novel Natural products (NPs) encoded by red soil-derived Streptomyces, we cocultured them with mycolic acid-containing bacteria (MACB) and compared the SM spectra and antimicrobial activity of the co-cultures and pure cultures
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Analysis of the genome sequences of Streptomyces and related genera revealed that they may contain a great variety of secondary metabolite (SM) biosynthetic gene clusters (BGCs) encoding novel NPs [5,6]. Around 40 novel NPs have been discovered from Streptomyces, and rare actinobacteria by co-culture with MACB strains These compounds comprise a variety of chemical scaffolds and bioactivities, validating this SM-BGC activation method of co-culture [16,17,18]. To activate the silent SM-BGCs of red soil-derived streptomycetes for NPs discovery, we selected 44 bioactive Streptomyces isolates and co-cultured them with four MACB of different species in a pairwise manner. Results of the study gain a deep insight into the NP biosynthetic potential of red soil-derived streptomycetes
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