Antimicrobial-producing microorganisms in fungus-farming ants: a critical review on insights into a natural biological defense with biotechnological potential

The main function of symbiotic actinobacterias in fungus-farming ants (Formicidae: Myrmicinae: Attini) is to protect the cultivated fungus against the pathogenic fungus Escovopsis spp. The microorganisms with the highest antimicrobial potential are actinobacterias, specifically Pseudonocardia and Streptomyces. These actinobacterias have demonstrated greater aggressiveness against the pathogen compared to other free-living actinobacterias, suggesting a selective process for strains with greater effectiveness in controlling the mycoparasite. Hypotheses explaining the coevolution between attinis and actinobacterias suggest that Pseudonocardia is a specialist symbiont that has coevolved with attinis, while Streptomyces is a mutualist recurrently adopted from the environment. In addition to actinobacterias, other microbial groups such as yeasts and bacteria with antimicrobial potential have been reported. The diversity of biomolecules synthesized by attini microsymbionts suggests that the microbiota of these insects could be an underexplored source of biotechnological resources with potential for combating agricultural and clinical diseases. This review addresses the antimicrobial potential of the microbiome associated with fungus-farming ants, and also analyzes aspects of coevolution, eco-physiological roles, and the diversity of microorganisms with antimicrobial potential.