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Endosymbiotic bacteria in the parasitic ciliate Ichthyophthirius multifiliis

H Y Sun1, J Noe, J Barber

  • 1Department of Infectious Diseases, The University of Georgia, Athens, GA 30602, USA.

Applied and Environmental Microbiology
|October 13, 2009
PubMed

Insights

Endosymbiotic bacteria, including Rickettsiales and Sphingobacteria, were found within the parasitic ciliate Ichthyophthirius multifiliis. Flavobacterium columnare was associated externally, not as an endosymbiont.

Area of Science:

  • Microbiology
  • Parasitology
  • Ichthyology

Background:

  • Ichthyophthirius multifiliis is a significant parasitic ciliate affecting freshwater fish.
  • Understanding the microbial communities associated with fish pathogens is crucial for disease management.

Purpose of the Study:

  • To identify and characterize bacterial endosymbionts within the parasitic ciliate Ichthyophthirius multifiliis.
  • To differentiate between endosymbiotic and externally associated bacteria.

Main Methods:

  • Polymerase chain reaction (PCR) amplification and sequencing of bacterial 16S rRNA genes from I. multifiliis isolates.
  • DAPI staining and transmission electron microscopy (TEM) to visualize endosymbionts.
  • Fluorescence in situ hybridization (FISH) to confirm the location and identity of bacterial endosymbionts.

Main Results:

  • PCR and sequencing revealed the presence of Alphaproteobacteria (Rickettsiales), Sphingobacteria, and Flavobacterium columnare DNA.
  • DAPI staining and TEM confirmed the presence of endosymbionts in the cytoplasm, resembling Rickettsia.
  • FISH confirmed Rickettsiales and Sphingobacteriales as endosymbionts within the ciliate cytoplasm.
  • F. columnare was not detected as an endosymbiont, suggesting external association.

Conclusions:

  • Ichthyophthirius multifiliis harbors endosymbiotic bacteria from the Rickettsiales and Sphingobacteriales classes.
  • Flavobacterium columnare is likely an external associate rather than an endosymbiont.
  • The functional role of these endosymbionts in the life cycle of I. multifiliis remains to be elucidated.

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