Differences in gene expression of the ciliate Paramecium caudatum caused by endonuclear symbiosis with Holospora obtusa, revealed using differential display reverse transcribed PCR

We identified six genes of Paramecium caudatum, which differentially expressed in Holospora obtusa-bearing and H. obtusa-free cells using differential display reverse transcribed PCR (DDRT-PCR). Northern blot analyses revealed that two of the genes, CA10-3 and CA20-2, were expressed extensively in the H. obtusa-free cell, while the other four, AS16-1, CS14, CS21 and CA17-1, were expressed more in the H. obtusa-bearing cell. Putative amino acid sequences of CA10-3, AS16-1 and CA17-1 showed high homologies with known genes related to intracellular signaling, transcription and aerobic metabolism. CS14 and CS21 also showed homologies with some genes whose products are still functionally unknown, but CA20-2 encoded a novel protein. We show in this study that H. obtusa alters multiple gene expression of the host after establishing endosymbiosis.

Paramecium caudatum acquires heat-shock resistance in ciliary movement by infection with the endonuclear symbiotic bacterium Holospora obtusa

Holospora obtusa is a macronucleus-specific bacterium of the ciliate Paramecium caudatum. Three types of P. caudatum cells (H. obtusa-free cells, cells bearing the reproductive form of H. obtusa and cells bearing the predominantly infectious form of H. obtusa) cultured at 25 degrees C were transferred to 4, 10, 25, 35 and 40 degrees C and their swimming velocities were measured by taking photomicrographs with two-second exposures. The H. obtusa-free cells almost ceased swimming at both 4 and 40 degrees C, while cells bearing the reproductive form and those bearing the predominantly infectious form actively swam even at these temperatures. These results show that the host cell can acquire heat-shock resistance when infected by H. obtusa in the macronucleus. This is the first evidence to show that the endonuclear symbiont Holospora contributes to maintain the ciliary movement of the host even at temperatures unsuitable for the host growth.

Initial steps of infection of the ciliate Paramecium with bacteria Holospora sp

New light and electron microscope data on the initial steps of endocytobiosis establishment between the ciliate Paramecium and specific intranuclear bacteria Holospora are provided. At the cytoplasmic step of infection bacteria of all Holospora species are found in a vesicle originating from the membrane of the host cell phagosome. The association between host cell microfilaments and the bacterium bearing vesicle may suggest a possible involvement of the ciliate cytoskeleton in the transportation of bacteria to the host cell nucleus. The authors subdivide the process of infection into 6 steps. Some strains of P. caudatum never take up infectious Holospora bacteria in the course of phagocytosis.