Analysis of a new defense mechanism against microbial infections found in Paramecium

一旦草履虫被内共生细菌Holospora obtusa感染，宿主细胞对第二次加入的相同细菌的消化空泡形成能力降低，并且这种空泡形成的变化在第一次感染后4 h内诱导。H.如果宿主之前还没有被细菌感染，那么带有钝角的宿主细胞可以摄取各种细菌。这些表明草履虫能够区分和记忆传染性全孢菌，并获得未知的二次感染防御机制。治疗继发性感染H. obtusa与脂肪酶，蛋白酶K，溶细胞酶，α-甘露糖苷酶，或β-半乳糖苷酶没有影响主机消化液泡的形成。此外，治疗的第二个增加了感染H。obtusa和宿主的抗250-kDa细胞表面蛋白的脱共生副寄生虫的抗体是无效的。这种现象是可重复的，但分子机制仍然是未知的。

Once Paramecium caudatum has been infected by endosymbiotic bacterium Holospora obtusa, the host cells become reduced the ability for digestive vacuole formation to the secondary added same bacteria, and that this change in the vacuole formation is induced within 4 h after the first infection. H. obtusa-bearing host cells can ingest various bacteria if the host has not yet been infected before by them. These suggest that Paramecium can distinguish and memory the infectious Holospora and acquires an unknown defense mechanism for the secondary infection. Treatment of the secondary added infectious H. obtusa with Lipase, Proteinase K, Lyticase, alpha-mannnosidase, or beta-galactosidase did not affect the host digestive vacuole formation. Also, treatments of the secondary added infectious H. obtusa and the host with antibodies for a 250-kDa cell surface protein of aposymbiotic paramecia are not effective. This phenomenon is repeatable, but molecular mechanism is still unknown.