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ORIGINAL RESEARCH article

Front. Mol. Biosci.

Sec. Genome Organization and Dynamics

Volume 12 - 2025 | doi: 10.3389/fmolb.2025.1648097

Serovar-Specific Genomic Features of Leptospira interrogans Hardjo: Implications for Host Adaptation

Provisionally accepted
Klaudia  DubniewiczKlaudia Dubniewicz1*Laura  PardyakLaura Pardyak1Artur  GurgulArtur Gurgul2Igor  JasielczukIgor Jasielczuk2Tomasz  SzmatołaTomasz Szmatoła2Zbigniew  ArentZbigniew Arent1*
  • 1Department of Infectious Diseases and Public Health, Faculty of Veterinary Medicine, University of Agriculture, Krakow, Poland
  • 2Department of Basic Sciences, Faculty of Veterinary Medicine, University of Agriculture, Krakow, Poland

The final, formatted version of the article will be published soon.

Introduction: Leptospirosis, caused by Leptospira spp., is one of the most widespread zoonoses worldwide. It affects both domestic and wild animals, with ruminants serving as a primary reservoir for serovar Hardjo. This serovar causes long-term colonisation of the kidney and genital tract. Hardjo strains are taxonomically assigned to two Leptospira species: L. interrogans and L. borgpetersenii. However, the molecular basis of L. interrogans serovar Hardjo adaptation remains poorly understood. Comparative genomic analysis of L. interrogans strains classified as the Hardjo serovar and other non-Hardjo serovars of the same species may help identify genetic determinants associated with host adaptation and species-specific cellular immune responses. Unfortunately, these pathogens are highly fastidious, and only a limited number of whole genomes have been sequenced to date. Materials and Methods: Four L. interrogans serovar Hardjo European isolates were sequenced. Using these new sequences alongside publicly available genomes of L. interrogans strains classified as Hardjo and non-Hardjo serovars, we performed comparative genomic analyses. Results: Hardjo strains formed a distinct phylogenetic clade and harboured unique variants, including an intact cas3 gene and a modified thiM start codon. We identified 88 Hardjo-specific orthologues, some located in putative genomic islands outside rfb locus. Several encoded proteins related to mobile elements, toxin-antitoxin systems or signal transduction. Enhanced biofilm formation in Hardjo strains supports a host-adapted phenotype. Conclusion: This study expands the genomic dataset for L. interrogans serovar Hardjo and provides novel insights into its genetic distinctiveness, suggesting potential factors that may facilitate colonisation and persistence in ruminant hosts.

Keywords: Leptospira interrogans, Hardjo, Comparative genomics, whole genome sequencing, Europe

Received: 16 Jun 2025; Accepted: 06 Aug 2025.

Copyright: © 2025 Dubniewicz, Pardyak, Gurgul, Jasielczuk, Szmatoła and Arent. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence:
Klaudia Dubniewicz, Department of Infectious Diseases and Public Health, Faculty of Veterinary Medicine, University of Agriculture, Krakow, Poland
Zbigniew Arent, Department of Infectious Diseases and Public Health, Faculty of Veterinary Medicine, University of Agriculture, Krakow, Poland

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