Species-specificity of Chlorella for establishment of symbiotic association with Paramecium bursaria — Does infectivity depend upon sugar components of the cell wall?

Abstract

Summary The symbiotic association between Paramecium bursaria and Chlorella was studied by means of infection experiments, using 20 strains taken from 9 different species of Chlorella and 5 stocks of algae-free P. bursaria which originated from different localities. At the time of infection, the ciliate had ingested numerous algal cells in all stocks that had been examined. Although the ingested algal cells in 5 species completely disappeared from the ciliate within several days, the cells of C. vulgaris, C. kessleri, C. sorokiniana and zoochlorellae were retained in all stocks of the ciliate even after a period of 2 months. It has been confirmed that all “infection-capable” Chlorella species including zoochlorella are distinguished by the presence of glucosamine as a chemical component in their rigid walls, whereas the rigid walls of “infection-incapable” species contain glucose and mannose. When these facts are taken into consideration, it may be shown that the various species of “Chlorella” hold the key to determine the selection of alga by the ciliate. Moreover, the presence of glucosamine in the rigid wall of alga would seem to be a prerequisite in determining the symbiotic association between Paramecium bursaria and Chlorella.