Associations
Pseudomicrothorax dubius with numerous endosymbiotic cells of 'Candidataus Cryptoprodotis polytropus', detected through fluorescence in situ hybridisation (FISH). Ferrantini et al. (2009) Journal of Eukaryotic Microbiology 56(2): 119-129. Published online: 3 March 2009. DOI: 10.1111/j.1550-7408.2008.00377 © Wiley-Blackwell.
Symbiotic associations between ciliates and bacteria have been reported for over 150 years. However, the presence of symbionts in Pseudomicrothorax dubius was unknown until 2009.
In a recent study, the bacterium 'Candidatus Cryptoprodotis polytropus' - a novel Rickettsia-like organism (RLO) - was found in large numbers in the cytoplasm of a population of P. dubius from Italy (Ferrantini et al., 2009).
RLOs are intracellular pathogens, usually highly infectious. They infect a variety of invertebrate and vertebrate hosts and cause severe mortality outbreaks in farmed aquatic species.
The presence of a previously unknown RLO in P. dubius suggests that ciliates may play key roles as hosts, vectors or natural reservoirs of some economically important pathogens.