American Society of Hirudotherapy

Hitchhiking of host biology by beneficial symbionts enhances transmission

Research article published in Sci Rep (2014)

Last Updated: June 18, 2026Reviewed by: ASH Editorial Board
Research article — evidence reviewArticle reference
Evidence: Preclinical (animal)Safety & Infection ControlOtt BM et al. · Sci Rep, 2014

Abstract

Transmission plays a key role in the evolution of symbiosis. Mixed mode transmission combines horizontal and vertical mechanisms for symbiont acquisition. However, features that enable mixed transmission are poorly understood. Here, we determine the mechanistic basis for the recruitment of the beneficial bacterium, Aeromonas veronii by the leech, Hirudo verbana. We demonstrate that host mucosal secretions complement imperfect symbiont vertical transmission. First, we show that the A. veronii population within secretions originates from the host digestive tract and proliferates synchronously with shedding frequency, demonstrating the coupling of partner biology. Furthermore, leeches are attracted to these castings with oral contact proving sufficient for symbiont transmission. Leech attraction to mucus is not affected by the symbiont state of either the host or mucus, suggesting that A. veronii exploits preexisting host behavior and physiological traits. A dual transmission mode, integrating multiple layers of host contributions, may prove evolutionarily advantageous for a wide range of symbioses. Using such a strategy, host infection is ensured, while also providing access to a higher genetic diversity of symbionts. Countless host-associated microbes exhibit mixed mode transmission, supporting the use of the leech symbiosis as a model for enhancing our understanding of the specificity, establishment and persistence of microbiotas.

Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.

Publication typeJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.
Indexed MeSH termsAeromonasAnimalsAnti-Bacterial AgentsBehavior, AnimalGastrointestinal TractGram-Negative Bacterial InfectionsLeechesMucusSymbiosis

Summary

Mucosal secretions complement vertical transmission of Aeromonas veronii in Hirudo verbana; mixed mode transmission integrates host contributions to ensure infection.

Why This Matters for Hirudotherapy

This study investigated the mechanistic basis of symbiont transmission in the leech Hirudo verbana, demonstrating that host mucosal secretions complement imperfect vertical transmission of the beneficial bacterium Aeromonas veronii, and that leeches are attracted to these secretions, enabling oral symbiont acquisition through a mixed-mode transmission strategy. The abstract proposes the leech symbiosis as a model for understanding microbiota specificity, establishment, and persistence across host-associated microbial systems. This work is relevant to ASH's domain as it advances basic biological understanding of a medicinal leech species. However, the study focuses on symbiont transmission dynamics and does not address hirudotherapy, therapeutic applications, clinical outcomes, or bioactive components of the leech secretome.

Citation

Hitchhiking of host biology by beneficial symbionts enhances transmission.

Ott BM et al. · Sci Rep, 2014

DOI

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