Giant Phages Build Private Bunkers Inside Bacteria

Viruses typically operate by injecting their genetic material into a host and hijacking its machinery, but 'nucleus-forming phages' employ a far more robust strategy. These so-called 'jumbo phages'—viruses with exceptionally large genomes—build a physical protein shell inside the bacterial cell. This barrier, primarily composed of a protein known as chimallin, isolates the viral genome, effectively excluding the host's immune enzymes that would otherwise destroy it.

In a comprehensive genetic survey, researchers utilised advanced modelling tools like RoseTTAFold to scan 16 million published sequences. They successfully identified 1,103 genomes of these fortress-building viruses, classifying them into 21 unique clusters. The analysis showed that these phages possess sophisticated genes for DNA repair and replication, allowing them to thrive in diverse environments. Notably, the team discovered these distinct viral lineages in human oral samples. This confirms that these complex, self-protecting viruses are not only widespread in nature but also play a role in the microbial communities residing within us.