Viral predation exerted by bacteriophages (or phages) has driven the continual evolution of diverse antiphage defense mechanisms. The majority of the antiphage defense systems described so far act at the cellular level targeting the process of phage infection at various levels1. Considering that Streptomyces spp. are characterized by a complex developmental lifestyle, which is intricately linked to the production of specialized metabolites and other molecules like proteins, we hypothesize that these multicellular bacteria also evolved strategies aiming at the inactivation of free phages after bursts of infections. This would ultimately protect the younger, more susceptible regions of the mycelium from phage attacks, thereby conferring protection on a multicellular level.
To test this, we screened different Streptomyces spent media and observed that some lead to the inactivation and degradation of extracellular phage particles. We further observed that a burst of infection of a Streptomyces culture is frequently followed by regrowth of phage-resistant mycelium coinciding with a significant drop in the titer of infectious phage particles. Efforts aiming at dissecting the observed phenomenon underline the importance of mycelial development and the transient secretion of antiphage molecules2.
Taken together, these results on extracellular phage degradation and the development of phage-resistant mycelium highlight the diverse multicellular strategies3,4 employed by Streptomyces in the defense against their most abundant predator.
1Bernheim, A. & Sorek, R., (2020). doi:10.1038/s41579-019-0278-2
2Luthe, T. et al., (2023). doi:10.1016/j.mib.2023.102314
3Luthe, T. et al., (2023). doi:10.1093/femsml/uqad002
4Kever, L. et al., (2024). doi:10.1093/femsml/uqae015