Interactions at the Streptomyces - animal interface: ecology, defence and disease

Streptomyces are filamentous, spore-forming members of the Actinomycetota, renowned for their capacity to produce chemically diverse, specialized metabolites with medically important properties. Traditionally, Streptomyces have been viewed as soil-dwelling microbes, and their roles in soil ecology, plant health and plant disease have been extensively studied. However, advances in metagenomic sequencing and molecular approaches have greatly expanded our ability to investigate interkingdom interactions between Streptomyces and more complex organisms, including animals. In recent years, a growing body of work has revealed diverse and often intimate associations between Streptomyces and members of the Animalia. These include interactions with microfauna such as nematodes (Nematoda), insects (Insecta), including bees and ants, mammals such as bats (Chiroptera) and humans (Homo sapiens). This review consolidates our current knowledge of Streptomyces - animal interactions, with a particular focus on chemical ecology and the roles of specialized metabolites in shaping these relationships. This work highlights the emerging body of work investigating the role of Streptomyces ecology beyond soil ecosystems and draws attention to the importance of exploring non-traditional niches, including animal-associated microbiomes, to deepen our understanding of microbial-animal interactions and to expand opportunities for natural product discovery.