title: Sensitivity of the infectious long form of the macronuclear endosymbiont Holospora obtusa of the ciliate Paramecium caudatum against chemical and physical factors.
abstract: Effects of various temperatures, pHs and drugs on the morphology, infectivity to the macronucleus of Paramecium caudatum (ability to penetrate macronuclear membrane), and reproductive ability of the infectious long form of Holospora obtusa were examined. The infectivity was not lost between pH 3-12, suggesting that acidosomal fusion with the bacteria-bearing food vacuoles does not inactivate the bacterial infectivity because pH in the food vacuoles at the maximum acidification has been known to be 3. However, bacteria treated with 220 μg/ml α-mannosidase could not infect the macronucleus though they could invade the host cytoplasm, via food vacuoles. This indicates that the bacteria have to escape from the food vacuole and invade the host cytoplasm within 8 min after being engulfed into the food vacuoles for successful infection, because it is known that the lysosomal fusion occurs at 8 min and a-mannosidase activity has been detected in P. caudatum. Other glycoside hydrolases and proteases examined did not affect the bacteria. The bacteria could be kept at -85°C for 6 months without any damage, but they easily lost the infectivity at temperatures higher than 30°C. Treatments with 250 units/ml penicillin and 0.25 % (w/v) kanamycin for 1 week at 25°C did not affect the bacteria, suggesting that the infectious long form is metabolically inactive. The bacteria became cell-wall ghosts in 50 % (w/v) acetic acid and soon lysed in 0.5 N NaOH, but hardly lysed in various detergents used.
authors.affiliation: Biological Institute, Faculty of Science, Yamaguchi University, Yamaguchi, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Fujishima
authors.forename: K
authors.initials: K
authors.lastname: Nagahara
authors.forename: Y
authors.initials: Y
authors.lastname: Kojima
authors.forename: Y
authors.initials: Y
authors.lastname: Sayama