American Society of Hirudotherapy

Leeches and their microbiota: naturally simple symbiosis models

Review published in Trends in Microbiology (2006)

Last Updated: June 18, 2026Reviewed by: ASH Editorial Board
Research article — evidence reviewArticle reference
Evidence: Narrative reviewGenomics & ProteomicsGraf J, Kikuchi Y, Rio RV · Trends in microbiology, 2006

Abstract

Strictly blood-feeding leeches and their limited microbiota provide natural and powerful model systems to examine symbiosis. Blood is devoid of essential nutrients and it is thought that symbiotic bacteria synthesize these for the host. In this review, three distinct leech-microbe associations are described: (i) the mycetome, which is the large symbiont-containing organ associated with the esophagus; (ii) the nephridia and bladders that form the excretory system; and (iii) the digestive tract, where two bacterial species dominate the microbiota. The current knowledge and features of leech biology that promote the investigation of interspecific interactions (host-microbe and microbe-microbe) and their evolution are highlighted.

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

Publication typeJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.Review
Indexed MeSH termsAnimalsBacteriaLeechesModels, BiologicalPhylogenyRNA, Ribosomal, 16SSymbiosis

Summary

Review of three distinct leech-microbe associations (mycetome, nephridia/bladders, digestive tract) demonstrating leeches as natural model systems for examining host-microbe and microbe-microbe symbiosis.

Why This Matters for Hirudotherapy

This review describes three leech-microbe associations—the mycetome (a symbiont-containing organ associated with the esophagus), the nephridia and bladders of the excretory system, and the digestive tract where two bacterial species dominate the microbiota. It highlights features of leech biology that promote investigation of host-microbe and microbe-microbe interactions and their evolution, noting that symbiotic bacteria are thought to synthesize essential nutrients absent from blood. The abstract discusses symbiosis biology and evolution only, with no mention of medicinal use, infection risk, or any therapeutic application. For ASH, this is background on leech-microbe symbiosis; the abstract does not establish a connection to hirudotherapy or the leech secretome, and the review provides no clinical data or recommendations.

Citation

Leeches and their microbiota: naturally simple symbiosis models.

Graf J, Kikuchi Y, Rio RV · Trends in microbiology, 2006

DOI

Added to ASH library: May 26, 2026 · Site last updated: June 18, 2026

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