Effect of Exposure Period and Algal Concentration on the Frequency of Infection of Aposymbiotic Ciliates by Symbiotic Algae from Paramecium bursaria

Abstract

SYNOPSIS The effect of exposure period and concentration of algae on the frequency of infection of aposymbiotic ciliates by algae obtained from the same clone of Paramecium bursaria syngen 2, was studied. The frequency of infection was roughly proportional to the algal concentration and to the exposure time of ciliates to algae. The relationship of algal concentration to infection frequency closely fitted the Poisson distribution curve for N = 1, suggesting that the minimum number of algae required to infect a single ciliate is 1. However, the data also strongly suggested that the average number of algae required to initiate infection of an average ciliate was ˜ 1,000. Three possible resolutions of this situation are: (a) the selection by the ciliate of a rare infective variant from a heterogeneous population: (b) the rare escape of an alga from digestion by the ciliate; and (c) the requirement for a large number of algae‐ciliate contacts to induce susceptibility in the ciliate. Splitting the exposure of ciliates to algae into 2 periods of 0.5 h, separated by 5 h in the absence of algae, produced a much higher frequency of infection than a single l‐h exposure, supporting the suggestion that the large number of algae is required to induce susceptibility in the ciliate which can then be infected by as few as a single algal cell.

Intracellular symbiosis of algae with possible involvement of mitochondrial dynamics

“…The host and the symbiotic zoochlorella can be cultured discretely and the endosymbiotic relationship can be re-established simply by co-culturing the two organisms 12–14 . Aposymbiotic P .…”

Acquired Phototrophy in Ciliates: A Review of Cellular Interactions and Structural Adaptations1

“…These findings support previous studies, demonstrating that perialgal vacuoles are formed from food vacuoles that have fused with acidosomes, but have not yet bound with lysosomes (Meier and Wiessner 1989). Most studies have reported that Chlorella cells are ingested in groups and that few cells survive the process of digestion (Karakashian and Karakashian 1973; Kodama and Fujishima 2009b; Meier and Wiessner 1989; Weis and Ayala 1979), particularly those that are naive to endosymbiosis (Kodama, Nakahara, and Fujimura 2007). …”

Forced symbiosis betweenSynechocystisspp. PCC 6803 and apo-symbioticParamecium bursariaas an experimental model for evolutionary emergence of primitive photosynthetic eukaryotes

“…8 Occasionally, apo-symbiotic cells of P. bursaria (thus lacking algae) can be found in natural water environments 9 and also in dark-grown culture of P. bursaria. 10 Interestingly, alga-free cell strains of P. bursaria can be artificially prepared by treating the stocks of green paramecia with cycloheximide 11 or some Key words: green paramecia, cyanobacteria, evolution, diagostic PCR, Escherichia coli, food vacuole herbicides. 12,13 Some groups have shown that independently cultured apo-symbiotic host cells and ex-symbiotic algae can re-associate and re-establish the symbiotic relationship.…”