This study shows how the bacterial retron Eco2 defends against viruses. Phage nucleases trigger activation of Eco2, which cuts RNAs, shuts down protein production and stops phage replication.

Most mitochondrial proteins are produced in the cytosol and imported through the translocase of the outer mitochondrial membrane (TOM) to reach their final destination. Although this protein entry gat...

From populations of multicellular organisms to selfish genetic elements, conflicts between levels of biological organization are central to evolution. Plasmids are extrachromosomal, self-replicating g...

Antiviral immune systems diversify by integrating new genes into existing pathways, creating new mechanisms of viral resistance. We identified genes encoding a predicted nuclease paired with a trypsin...

An exploration of previously undescribed variants from the long tail of the CRISPR–Cas distribution.

Proximity-ligation-based sequencing from 111 samples and 5 environments reveals that a substantial proportion of phages infect multiple species.

Transposon-encoded TnpB nucleases gave rise to type V CRISPR-Cas12 effectors through multiple independent domestication events. These systems use diff…

Humans and animals are ubiquitously colonized by Enterobacteriaceae , a bacterial family that contains both commensals and clinically significant pathogens. Here, we report Enterobacteriaceae megaplasmids of up to 1.58 Mbp in length in infant and adult guts, and other microbiomes. Of the 19 complete plasmid genomes, one was reconstructed from an Escherichia coli isolate; others were linked to species of Citrobacter and Enterobacter via analysis of genome modification patterns. The detection of related plasmids in different Enterobacteriaceae , conjugation machinery, and more diverse modified motifs in certain plasmids compared to hosts suggests that these elements are self-transmissible, with a broad host range. The plasmids encode multi-drug efflux systems and potential secreted effectors. Up to 208 tRNAs are encoded, and include sequence variants that may counter tRNA-centric defense mechanisms. Overall, the vast megaplasmid coding capacity may broaden host range, increase competitiveness, control invasion by other elements, and counter programmed cell death. ### Competing Interest Statement The authors have declared no competing interest. National Institutes of Health, https://ror.org/01cwqze88, 5R01AI092531 Swiss National Science Foundation, IZJFZ3-177614 Biotechnology and Biological Sciences Research Council, https://ror.org/00cwqg982, BB/X011011/1, BBS/E/QU/230002A, BB/T008717/1 Chan Zuckerberg Initiative (United States), https://ror.org/02qenvm24 Finnish Multidisciplinary Centre of Excellence in Antimicrobial Resistance Research, 346127