Identification and characterization of small RNAs expressed by Leptospira borgpetersenii serovar Hardjo and their conservation in the genus Leptospira

Authors: Putz, Ellie; FERNANDES, LUIS - Oak Ridge Institute For Science And Education (ORISE); Bayles, Darrell; TIBBS-CORTES, BEINVENIDO - Oak Ridge Institute For Science And Education (ORISE); PETRY, BRUNA - Oak Ridge Institute For Science And Education (ORISE); SIVASANKARAN, SATHESH - Iowa State University; Nally, Jarlath

Submitted to: BMC Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2026
Publication Date: 4/18/2026
Citation: Putz, E.J., Fernandes, L.G., Bayles, D.O., Tibbs-Cortes, B., Petry, B., Sivasankaran, S.K., Nally, J.E. 2026. Identification and characterization of small RNAs expressed by Leptospira borgpetersenii serovar Hardjo and their conservation in the genus Leptospira. BMC Microbiology. https://doi.org/10.1186/s12866-026-05052-1.
DOI: https://doi.org/10.1186/s12866-026-05052-1

Interpretive Summary: Leptospires, atypical bacteria responsible for leptospirosis, are found world-wide in humans, companion and domestic animals, as well as the environment. In incidental hosts, severe disease can result in organ failure, and death while in asymptomatic reservoir hosts, bacteria typically colonize the kidneys and are excreted in the urine. Reproductive abortion is a feature in infected livestock. Different species, serovars, and even strains of leptospires may cause different presentations of disease in different host species which presents serious hurdles for the development of effective vaccines, diagnostics, and treatments. In an effort to characterize pathogen nuances, recent work has focused on genomic, transcriptomic, and proteomic characterization of leptospires. In this work, RNA sequencing identified for the first time the expression of small RNAs in two strains of Leptospira borgpetersenii serovar Hardjo, many of which are differentially expressed between the strains and in response to temperature. Within novel sRNAs characterized here, some were conserved across the genus Leptospira, while others were specific to the species and/or strain level. This highlights potential for using sRNAs in broad diagnostics and detection of leptospirosis as well as species and/or serovar specific distinction. The identification and characterization of sRNAs is essential to understand pathogenic mechanisms of leptospirosis and how leptospires regulate gene expression during host infection.

Technical Abstract: Leptospirosis is a global zoonotic disease affecting humans, companion animals, and domestic livestock. Clinical presentation of disease is dependent on complex interactions between host species and pathogenic species, serovars, and strains of Leptospira. This is exemplified by L. borgpetersenii serovar Hardjo strains HB203 and JB197, which differ very little by genome sequence but cause divergent clinical disease phenotypes in the hamster model of leptospirosis: JB197 causes an acute lethal disease while HB203 establishes a chronic asymptomatic infection of the kidneys. Shedding of leptospires from infected kidneys in urine is one of the primary modes of leptospirosis transmission. Leptospires can directly infect other hosts or indirectly persist in the environment highlighting the broad range of environmental cues encountered during disease transmission and infection. Previous work has shown that different strains of Leptospira modify their gene expression in response to temperature. This study reports 267 small RNAs (sRNAs) previously unannotated for L. borgpetersenii. RNA sequencing was performed on serovar Hardjo strains HB203 and JB197 cultured directly from experimentally infected hamsters at both 29°C and 37°C. Characterization of sRNAs and their expression revealed strain-specific sRNAs and differential expression between strains and temperatures. The nuances of what contributes to Leptospira strain-specific pathogenesis are poorly understood. Non-coding sRNAs have regulatory impacts on gene expression that can alter leptospire protein profiles, virulence factors, and host pathogen interactions. Additional analysis investigating the conservation of these sRNAs amongst the genus Leptospira revealed groups of both highly conserved sRNAs as well as species level profiles. This emphasizes the potential for sRNA use in broad clinical detection as well as species/serovar specific distinction.