--- DOAJ_listed: '1' OA_place: publisher OA_type: gold _id: '23090' abstract: - lang: eng text: 'Homologous recombination is ubiquitous across evolution, generating variation through genetic reshuffling. Although bacteria lack meiotic recombination, homologous recombination has been known to extensively shape their genomes. However, the mechanisms and ecological conditions sustaining frequent recombination in bacteria remain unclear. Using an Escherichia coli–P1 phage model system, we reveal how frequent recombination emerges from CRISPR-based herd immunity to a generalized transducing phage (DNA vector). Herd immunity maintains phage-susceptible donor bacteria, recipient immune bacteria, and transducing phage, which promotes chromosomal gene flow that exceeds spontaneous mutation by up to two orders of magnitude. Notably, recombination begins as bacterial cultures enter stationary phase, when canonical mutation supply through population growth and DNA replication is strongly reduced, and recombination can be reinitiated by brief fresh nutrient pulses. Genetic analysis showed that stationary-phase recombination requires recA, recB, and recG, connecting this process to a defined homologous recombination pathway, and suggests a plausible transcriptional regulatory link to transition to nutrient limitation. Bacterial herd immunity therefore has an unexpected evolutionary consequence: it can promote homologous recombination by turning phages into de facto pollinators. This mechanism can help explain how high rates of homologous recombination may be sustained across bacterial populations and suggests that bacterial immune systems can shape molecular evolution not only by blocking infection but also by regulating genetic exchange.' acknowledgement: We thank Stuart Baird, Nick Barton, Max Joesch, Meriem El Karoui, Mato Lagator, Ivana Mašlaňová, Stepan Ovchinnikov, Roman Pantůček, Maroš Pleška, Jitka Polechová, and Bryan Wu for their feedback on the manuscript. We are grateful to the Redlinger Hut for hosting many discussions about the project away from the daily buzz. We acknowledge the core facility CELLIM supported by the Czech-BioImaging large RI project (LM2023050 funded by MEYS CR) for their support. This work was supported by H2020 European Research Council EVOLHGT No. 648440 to JPB, European Commission Programme EXCELES project LX22NPO5103 “National Institute of Virology and Bacteriology” to PPl, and a bilateral Czech-Austrian mobility grant 8J3AT003 funded by MEYS CR and OeAD AT to PPa and CCG. article_number: msag238 article_processing_charge: Yes article_type: original author: - first_name: Pavel full_name: Payne, Pavel id: 35F78294-F248-11E8-B48F-1D18A9856A87 last_name: Payne orcid: 0000-0002-2711-9453 - first_name: Pavel full_name: Plevka, Pavel last_name: Plevka - first_name: Jonathan P full_name: Bollback, Jonathan P id: 2C6FA9CC-F248-11E8-B48F-1D18A9856A87 last_name: Bollback orcid: 0000-0002-4624-4612 - first_name: Calin C full_name: Guet, Calin C id: 47F8433E-F248-11E8-B48F-1D18A9856A87 last_name: Guet orcid: 0000-0001-6220-2052 citation: ama: Payne P, Plevka P, Bollback JP, Guet CC. Herd immunity underlies homologous recombination in stationary phase bacteria. Molecular Biology and Evolution. 2026;43(10). doi:10.1093/molbev/msag238 apa: Payne, P., Plevka, P., Bollback, J. P., & Guet, C. C. (2026). Herd immunity underlies homologous recombination in stationary phase bacteria. Molecular Biology and Evolution. Oxford University Press. https://doi.org/10.1093/molbev/msag238 chicago: Payne, Pavel, Pavel Plevka, Jonathan P Bollback, and Calin C Guet. “Herd Immunity Underlies Homologous Recombination in Stationary Phase Bacteria.” Molecular Biology and Evolution. Oxford University Press, 2026. https://doi.org/10.1093/molbev/msag238. ieee: P. Payne, P. Plevka, J. P. Bollback, and C. C. Guet, “Herd immunity underlies homologous recombination in stationary phase bacteria,” Molecular Biology and Evolution, vol. 43, no. 10. Oxford University Press, 2026. ista: Payne P, Plevka P, Bollback JP, Guet CC. 2026. Herd immunity underlies homologous recombination in stationary phase bacteria. Molecular Biology and Evolution. 43(10), msag238. mla: Payne, Pavel, et al. “Herd Immunity Underlies Homologous Recombination in Stationary Phase Bacteria.” Molecular Biology and Evolution, vol. 43, no. 10, msag238, Oxford University Press, 2026, doi:10.1093/molbev/msag238. short: P. Payne, P. Plevka, J.P. Bollback, C.C. Guet, Molecular Biology and Evolution 43 (2026). corr_author: '1' das_tickbox: '1' dataavailabilitystatement: The data underlying this article are available in the article and in its online material. date_created: 2026-10-11T22:02:04Z date_published: 2026-10-03T00:00:00Z date_updated: 2026-10-12T10:51:54Z day: '03' ddc: - '570' department: - _id: CaGu doi: 10.1093/molbev/msag238 external_id: pmid: - '42827080' fulldoi: https://doi.org/10.1093/molbev/msag238 has_accepted_license: '1' intvolume: ' 43' issue: '10' keyword: - homologous recombination - defense systems - CRISPR-Cas - herd immunity - stationary phase - bacterial evolution language: - iso: eng main_file_link: - open_access: '1' url: https://doi.org/10.1093/molbev/msag238 month: '10' oa: 1 oa_version: Published Version pmid: 1 publication: Molecular Biology and Evolution publication_identifier: eissn: - 1537-1719 issn: - 0737-4038 publication_status: epub_ahead publisher: Oxford University Press quality_controlled: '1' researchdata_availability: no scopus_import: '1' status: public supplementarymaterial: yes title: Herd immunity underlies homologous recombination in stationary phase bacteria tmp: image: /images/cc_by_nc.png legal_code_url: https://creativecommons.org/licenses/by-nc/4.0/legalcode name: Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) short: CC BY-NC (4.0) type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 43 year: '2026' ...