The origin, risks, diagnosis, epidemiology of resistance to antibacterial agents in man and livestock worldwide, as well as preventive and countermeasures, in a « one health » perspective.

Resource supply is generally considered a dominant driver of microbial diversity. Here, using a four-species bacterial consortium, we asked whether...

Nature Communications - Beyond resistance and tolerance: rethinking evolutionary responses to antibiotics from the perspective of individual bacterial cells

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

npj Antimicrobials and Resistance - Mechanistic insights into plasmid transfer inhibition in Enterobacterales by nucleoside analogues

Ponemos el foco en un estudio que identifica un nuevo mecanismo por el que los plásmidos pueden acelerar la aparición de resistencia a los antibióticos

Bacterial biofilms dominate microbial life; however, their evolutionary genetics remain incompletely understood. Extensive replication of biofilm selection experiments by secondary school students can...

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

Abstract. Understanding the drivers and consequences of horizontal gene transfer (HGT) is a key goal of microbial evolution research. Although co-occurring

Abstract. Conjugative plasmids are key drivers of bacterial adaptation, enabling the horizontal transfer of accessory genes within and across diverse micro

Plasmids are extrachromosomal DNA molecules that spread by horizontal transfer and shape bacterial evolution. Plasmids are typically present at mul...

The cellular context interacts with genetic circuits, decisively defining their performance. However, contextual dependencies (the interplay between the host and the circuit) are often difficult to en...

Conjugative plasmids play an important role in the spread of antimicrobial resistance (AMR) genes among pathogenic bacteria. This study shows that AMR loss in evolving populations is associated with t...

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...

Bacteria employ a range of competition systems that deliver toxins to inhibit competing strains. This study shows that these systems are particularly important for the ecology of virulent and antibiot...

The nature of standing genetic variation remains a central debate in population genetics, with differing perspectives on whether common variants are almost always neutral as suggested by neutral and n...

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...

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...

Adherent-invasive strains of E. coli are commonly isolated from patients with Crohn’s disease. Here, the authors show that an AIEC harbours a hybrid Type IV secretion system (T4SS) that mediates pilin...

This study investigates the effects of the carbapenem resistance plasmid pOXA-48 in clinical enterobacteria. Using CRISPRi screens, the authors revealed that the carbapenemase OXA-48 has a role in the plasmid-associated fitness costs.

Phage therapy is a promising alternative to antibiotics to treat multidrug resistant infections. Plasmid dependent phages (PDPs) are particularly attractive as therapeutics because they can both kill ...