Whitespot parasites contain symbiotic bacteria

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Researchers from China and the USA have discovered the presence of symbiotic bacteria living within the protozoan responsible for white spot disease or ich (Ichthyophthirius multifiliis).

This discovery could open up new avenues to treat the disease. Using whole genome sequencing, Harry Dickerson and coauthors found the presence of three classes of bacteria associated with the protozoan: Alphaproteobacteria (Rickettsiales), Sphingobacteria, and Flavobacterium columnare.  

The presence of the first two as endosymbionts living within the cytoplasm of the protozoan were confirmed by microscopy, while the Flavobacterium is thought to adhere to the protozoan through association with cilia.  

Although the physiological relationship between the endosymbionts and the protozoa is not understood, the researchers are working to elucidate this and to find out if the protozoan would remain infective upon removal or inactivation of the endosymbionts.  

They hope that their findings would allow better treatments for ich to be developed.

For more information, see the paper: Sun, HY, J Noe, J Barber, RS Coyne, D Cassidy-Hanley, TG Clark, RC Findly and HW Dickerson (2009) Endosymbiotic bacteria in the parasitic ciliate Ichthyophthirius multifiliis. Applied and Environmental Microbiology 75, pp. 7445–7452.