Novel strains of Actinobacteria associated with neotropical social wasps (Vespidae; Polistinae, Epiponini) with antimicrobial potential for natural product discovery

Abstract

Antimicrobial resistance has been considered a public health threat. The World Health Organization has warned about the urgency of detecting new antibiotics from novel sources. Social insects could be crucial in the search for new antibiotic metabolites, as some of them survive in places that favor parasite development. Recent studies have shown the potential of social insects to produce antimicrobial metabolites (e.g. ants, bees, and termites). However, most groups of social wasps remain unstudied. Here, we explored whether Actinobacteria are associated with workers in the Neotropical Social Wasps (Epiponini) of Costa Rica and evaluated their putative inhibitory activity against other bacteria. Most isolated strains (67%) have antagonistic effects, mainly against Bacillus thuringensis and Escherichia coli ATCC 25992. Based on genome analysis, some inhibitory Actinobacteria showed biosynthetic gene clusters (BGCs) related to the production of antimicrobial molecules such as Selvamycin, Piericidin A1, and Nystatin. The Actinobacteria could be associated with social wasps to produce antimicrobial compounds. For these reasons, we speculate that Actinobacteria associated with social wasps could be a novel source of antimicrobial compounds, mainly against Gram-negative bacteria.

Keywords: actinobacteria; adults; antimicrobial compounds; inhibition; pathogen; social wasps.

Figure 1.

Social wasp nests of Polybia sp. (A) and (B), Metapolybia sp. (C), Chartergellus golfitensis (D), and Protopolybia sp. (E) selected for sample collection.

Figure 2.

Distribution of coding sequences based on the genome annotation and categorized in subsystems for six strains of wasp-associates actinobacteria (Saccharopolyspora sp. 6M, 6T, 6V, 7B, and Streptomyces sp. 7G and 8L).

Figure 3.

Maximum-likelihood phylogenetic tree based on the core genome of the isolated strains of the genus Saccharopolyspora (7B, 6M, 6V, and 6T, highlighted) and reference genomes selected from the NCBI GenBank database (identified as “QS” in blue), the automatically generated type genomes in autoMLST (identified as “TS” in green and gray), and the tree ancestor or “out-group” (identified as “OG” in red). Bootstrap support is indicated on the nodes and was obtained with 1000 replicates on the ultrafast method.

Figure 4.

Maximum-likelihood phylogenetic tree based on core genomes of the Streptomyces isolates (7G and 8L, highlighted) and reference genomes selected from the NCBI GenBank database (identified as “QS” in blue), the type genomes generated automatically in autoMLST (identified as “TS” in green and gray), and the out-group (identified as “OG” in red). Bootstrap support is indicated on the nodes and was obtained with 1000 replicates on the ultrafast method.

Figure 5.

Similarity gene plots between known antimicrobial related BGCs (Piericidin A1, Nystatin A1, and Selvamycin) and predicted BGCs from Saccharopolyspora sp. strains isolated from Neotropical social wasp. Genes with different functions are represented by colored boxes, where their function is associated to the color as indicated in the legend. Known clusters were obtained from MIBiG database and similar genes in the predicted BGCs are linked by solid black lines. Predicted BGCs and its genetic similarity were identified with AntiSMASH.