Viruses are ubiquitous in the environment, and organisms have developed various mechanisms to counter their threat. However, the genome of actinomycetes contains a highly conserved gene set encoding virus-like nanoparticles, although its biological significance has remained unclear.

In this study, researchers examined Streptomyces davawensis, an actinomycete species, and discovered that it produces virus-like particles that facilitate host reproduction. Extracellular DNA, which serves as a scaffold for multicellular organization, was significantly reduced in the colonies of mutant S. davawensis strains lacking virus-like particle production and cells trapped in abnormal aggregates. Detailed analysis revealed that the virus-like particles contain a unique enzyme (effector) crucial to their function, which partially degrades genomic DNA. The effector is released from the particle and localizes at the host cell membrane. The proposed model suggests that the effector partially degrades genomic DNA, bridging the intracellular and extracellular environments, thereby facilitating extracellular DNA release and providing a scaffold and nutrients for host cell reproduction. These findings reveal the exploitation mechanism of virus-related nanoparticles for bacterial proliferation and offer a novel strategy to reprogram virus-related nanoparticle functionality through modulation of effector activity for various applications in biotechnology.

This work was supported by a Grant-in-Aid for Scientific Research from the Japanese Society for the Promotion of Science (19K15726, 23K13863 and 23K26811), the Japan Science and Technology Agency (JPMJMI21G8 and JPMJGX23B2) and the Suntory Rising Stars Encouragement Program in Life Sciences (SunRiSE).

Journal reference:

Nagakubo, T., et al. (2024). Contractile injection systems facilitate sporogenic differentiation of Streptomyces davawensis through the action of a phage tapemeasure protein-related effector. Nature