Landscape of retron diversity across the SPIRE microbial metagenome resource reveals candidate novel type XI-like lineages.

Two candidate type XI-like retron lineages with unique architectures and accessory modules were identified across diverse microbial habitats in the SPIRE metagenome collection.

• Why it matters: Understanding retron diversity is crucial because these elements are involved in bacterial anti-phage defense and have potential biotechnological applications, yet their ecological distribution and structural variation remain poorly characterized.
• What they did: Researchers surveyed over 100,000 microbial metagenomes using hidden Markov models to identify retrons, revealing all canonical types and novel divergent lineages, including the two candidate type XI-like groups with protease-independent architectures.
• The result: The discovery of these new lineages broadens the known architectural diversity of retrons, supports conservation of RT-ncRNA organization despite sequence divergence, and provides a foundation for future functional and biotechnological studies.