Abstract. Interactions between bacteria, bacteriophages, and their satellites are shaped by a myriad of defence and counter-defence mechanisms. Here, we id

Nature Microbiology, Published online: 16 September 2026; doi:10.1038/s41564-026-02484-3An engineered non-pathogenic bacterium produces lytic phages and is protective in mouse models of Salmonella infection.

Plasmids drive bacterial adaptation, but how their diversity arises has remained unclear. Here, they show that in Staphylococcus aureus, mobile genetic elements repeatedly fuse and delete plasmids, re...

Recent discoveries on bacterial immunity have revealed that several protein domains involved in anti-phage defense are conserved in eukaryotes, such as SIRim, TIR, PNP and gasdermin. Bacterial immune ...

Nature Reviews Microbiology, Published online: 20 May 2026; doi:10.1038/s41579-026-01318-7The life cycle of temperate bacteriophages involves lytic or lysogenic cycles and has historically served as a model for studying genetic regulation. This Review provides an updated overview of these cycles and highlights their complexities, supporting a greater appreciation of the ecological roles of temperate phages.

Plasmids are DNA molecules that replicate independently of the bacterial chromosome and are typically associated with the spread of antimicrobial resistance (AMR) and virulence determinants, among other relevant traits. Fusion events between plasmids generate larger, complex backbones that carry two or more replication systems, known as multireplicon plasmids. Despite decades of study, we are still far from understanding how multireplicon plasmids arise, persist, and shape the evolution of AMR. Here, we analyzed 24,000 non-redundant plasmids across bacterial genera and found that more than 30% of them encoded multiple replicons. Compared to single-replicon plasmids, multireplicon plasmids were larger, were enriched in genes encoding antimicrobial, metal, and biocide resistance as well as virulence factors, and showed higher mobility and a broader host range. We also found that multireplicon assembly is not random. Some replicon pairs repeatedly merge into stable multireplicon plasmids, while other pairs rarely fuse even when they commonly coexist intracellularly. We also show that replicon pairs tend to be localized either in close proximity to one another or on opposite poles of the plasmid. We further highlight that multireplicon plasmids can be broadly classified into two groups: long-term coevolving replicon pairs and transient associations that lack a shared evolutionary history. Finally, we reveal the molecular mechanisms underlying multireplicon formation and highlight the role of insertion sequences in their formation and maintenance. Together, our work sheds light on the abundance, gene content, evolutionary patterns, and formation dynamics of multireplicon plasmids and pinpoints their relevance to bacterial evolution and human health. ### Competing Interest Statement The authors have declared no competing interest. Instituto de Salud Carlos III, https://ror.org/00ca2c886, PI23/01945, PFIS - FI22/00265, Miguel Servet - CP22/00164 European Research Council, https://ror.org/0472cxd90, HorizonGT, 101077809 Fundación Ramón Areces, "Ayudas Fundación Ramón Areces para la realización de Tesis Doctorales en Ciencias de la Vida y de la Materia 2025" Coordenação de Aperfeicoamento de Pessoal de Nível Superior, https://ror.org/00x0ma614, 88881.128025/2025-01

Gallego-del-Sol et al. show that arbitrium-coding phages can sense non-cognate peptide signals from other phages to regulate lysis-lysogeny decisions. This crosstalk affects lysis-lysogeny outcomes of...

Inactivation of chromosomal genes through plasmid-encoded IS elements is an extended mechanism of antimicrobial resistance evolution in bacteria.

Sabnis et al. explain why non-conjugative plasmids move at a low rate in nature. While increased mobility can easily evolve by incorporating phage DNA into plasmids, this is disadvantageous because it...