Flow cytometry as a strategy to study the endosymbiosis of algae inParamecium bursaria

Abstract

Background The stable symbiotic association between Paramecium bursaria and algae is of interest to study such mechanisms in biology as recognition, specificity, infection, and regulation. The combination of algae‐free strains of P. bursaria, which have been recently established by treating their stocks of green paramecia with herbicide paraquat (Hosoya et al.: Zool Sci 12: 807–810, 1995), with the cloned symbiotic algae isolated from P. bursaria (Nishihara et al.: Protoplasma 203: 91–99, 1998), provides an excellent clue to gain fundamental understanding of these phenomena. Methods Flow cytometry and light microscopy have been employed to characterize the algal cells after they have been released from the paramecia by ultrasonic treatment. Algal optical properties such as light scattering and endogenous chlorophyll fluorescence intensity have been monitored for symbiotic and free‐living strains, and strains at stages of interaction with a host. Results Neither algal morphology nor chlorophyll content has been found to be altered by sonication of green paramecia. This fact allows to interpret in adequate degree changes in the optical properties of symbiont that just has been released from the association with a host (decreased forward light scatter and chlorophyll fluorescence signals). Optical characterization of both symbiotic and free‐living algal strains with respect to their ability to establish symbioses with P. bursaria showed that chlorophyll content per cell volume seems to be a valuable factor for predicting a favorable symbiotic relationship between P. bursaria and algae. Conclusions Flow cytometry combined with algae‐free paramecia and cloned symbiotic algae identifies algal populations that may be recognized by host cells for the establishment of symbioses. Cytometry 41:209–215, 2000 © 2000 Wiley‐Liss, Inc.

Life Cycle Analysis of Endosymbiotic Algae in an Endosymbiotic Situation with Paramecium bursaria Using Capillary Flow Cytometry

“…In fact, a few reports of the literature describe FCM analysis of intact P. bursaria host cells using an instrument nozzle of a special size: 200 µm diameter [46]. In terms of morphological usability of microalgae for FCM, more exosymbiotic algae isolated from P. bursaria than the host cells have been studied and analyzed using FCM [5,6,47]. Many data obtained only from their algae, however, are entirely inadequate to clarify the mechanisms underlying endosymbiosis or the life cycle of endosymbionts remaining in P. bursaria because these exosymbiotic algae have already been disengaged from control by the host [7,34].…”

“…The synchronous division between chloroplasts and each eukaryotic host cell is achieved in most algal species such as red and green algae, and in land plants in the following manner: each host cell dominantly regulates expression of the nucleus-encoded plastid division genes and proteins. Although organelles such as chloroplasts cannot become self-sustaining outside of an eukaryotic cell, exosymbiotic algae isolated from P. bursaria can proliferate independently from the host ciliate [5,25,47]. Endosymbiotic algae of P. bursaria, unlike organelles such as chloroplasts, are expected to be able to self-manage their cell cycle pace even if they remain in the host Paramecium.…”

Morphology and phylogenetic position of a trebouxiophycean green alga (Chlorophyta) growing on the rubber tree,Hevea brasiliensis, with the description of a new genus and species

“…Symbioses of Chlorella sp. with hydra and Paramecium bursaria are other examples (Rahat & Reich, 1984, 1985, Gerashchenko et al, 2000, in which green algae supply up to 69% of the host's caloric requirements when light is provided (Pardy & White, 1977). ''Back transfer'' of metabolites from food to endosymbiotic algae in the digestive cells of green hydra has also been demonstrated (Thorington & Margulis, 1981).…”

Effect of Japanese Paramecium bursaria Extract on Photosynthetic Carbon Fixation of Symbiotic Algae

“…CELLS of a green paramecium, Paramecium bursaria , contain several hundred endosymbiotic algae. The organism has been used as a subject for research on endosymbiosis because host cell and endosymbiont can be separated and reconstructed from the partners (Gerashchenko et al 2000; Nishihara et al 1998; Reisser 1986, 1988; Reisser and Widowski 1992). Studies using isolates or reconstructed organisms have shown that the features of the symbiont differ from those of free‐living Chlorella species in several ways, including high maltose production (Brechignac and Wolf 1994) and maltose excretion to the host (Brown and Nielsen 1974), ability to re‐infect the endosymbiont‐free host cells (Reisser, Radunz, and Wiessner 1982; Takeda et al 1998), and susceptibility to viruses specific to Chlorella (Van Etten et al 1983).…”