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DISARM (Defense Island System Associated with Restriction Modification) systems can provide bacteria with protection against a wide range of phage. Here, Bravo et al. determine cryo-EM structures of the core DISARM complex that shed light onto phage DNA recognition and activation of this widespread defense system.

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

The CRISPR–Cas (clustered regularly interspaced short palindromic repeats–CRISPR-associated proteins) systems are immunity systems that are present in many bacteria and archaea. Here, Koonin and colleagues present a new classification of these systems and introduce a new nomenclature of the genes in the CRISPR–casloci that better reflects the relationships between the proteins.

InstaNovo, a transformer-based model, and InstaNovo+, a multinomial diffusion model, enhance de novo peptide sequencing, enabling discovery of novel peptides, improved therapeutics sequencing coverage and detection of unreported organisms in proteomics studies

Here the authors describe CAPTURE, a versatile and sensitive protocol to detect spacer-acquisition events in native CRISPR arrays using nested PCR amplification and amplicon size selection.

Many phages use tails to attach to and penetrate the cell envelope of their bacterial hosts. In this Review, Brouns and colleagues explore recent structural and mechanistic insights into the interaction of phage tails with receptors on the bacterial surface.

Type III CRISPR-Cas systems recognize and cleave target RNAs and produce signalling molecules. Here the authors discover that both processes are governed by a flexible seed region, ultimately resulting in SCOPE, a SARSCoV-2 diagnostic assay with atto-molar sensitivity.

Here, the authors describe the global distribution of crAssphage, its presence in Old-World and New-World primates, and its association with gut bacterial communities and dietary factors, providing insights into the origin, evolution and epidemiology of human gut crAssphage.

Single-particle tracking PALM (sptPALM) provides quantitative information in vivo if the protein of interest remains in a single diffusional state during track acquisition. Here the authors develop a custom-built sptPALM microscope and a Monte-Carlo based diffusion distribution analysis to study dynamic DNA-dCas9 interactions in live bacteria.

In this Review, Brouns and colleagues discuss our current understanding of RNA-targeting type III and type VI CRISPR–Cas systems by detailing their composition, properties and defence processes, and describing the biological rationale behind the broad activated immune responses as an effective strategy to combat viral infection.

The jumbo contractile bacteriophage, Kp24, has been isolated from clinical strains of Klebsiella pneumonia. Here, the authors present structural and functional insight into the capsid, tail and tail fibres and how this impacts infectivity.

Cas1–Cas2 selects precursor prespacers from DNA fragments in a length- and PAM-sequence-dependent manner, and these precursors are trimmed by DnaQ exonucleases to enable integration into the CRISPR locus in the correct orientation.

Structures of the Cas4–Cas1–Cas2 complex from Geobacter sulfurreducens show that a 3′-overhang in the protospacer adjacent motif is required for complex assembly and spacer insertion into the CRISPR array.

Prokaryotic CRISPR-Cas systems provide adaptive immunity against foreign nucleic acids by acquiring short, invader-derived sequences called spacers. Here, Staals et al. analyse millions of such events in a native CRISPR-Cas system, showing that newly acquired spacers provoke additional rounds of spacer acquisition.

The CRISPR system is a prokaryotic immune system that depends on the Cascade protein complex and small guide RNAs (crRNAs). The Cascade complex, loaded with crRNA, is now characterized, the overall architecture of Cascade deduced, and the complex found to identify targets by formation of an R loop between the crRNA and dsDNA.

Here, Argonaute from the prokaryote Thermus thermophilus is shown to use small DNA guides to interfere directly with invading foreign DNA, rather than being involved in RNA-guided RNA interference, as observed in eukaryotes.

A type I CRISPR–Cas system, rather than the conventional type II CRISPR systems, is adapted for gene editing by fusing Cascade to the FokI nuclease domain.

CRISPR–Cas systems provide bacteria and archaea with adaptive immunity to invading foreign DNA. In an Analysis article, Koonin and colleagues update a previous classification of these systems to incorporate the large volume of genomic data generated in recent years.

The number and diversity of known CRISPR–Cas systems have substantially increased in recent years. In this Review, Koonin and colleagues provide an updated evolutionary classification of CRISPR–Cas systems and cas genes, with an emphasis on major developments, and outline a complete scenario for the origins and evolution of CRISPR–Cas systems.