Parasite-mediated protection against osmotic stress for Paramecium caudatum infected by Holospora undulata is host genotype specific.

Under certain conditions, otherwise parasitic organisms may become beneficial to their host. Parasite-mediated heat and osmotic stress resistance have been demonstrated for Paramecium caudatum, infected by several species of parasitic bacteria of the genus Holospora. Here, using the micronucleus-specific bacterium Holospora undulata, we investigate how infection mediates the response of two genotypes (clones 'K8' and 'VEN') of P.