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Review
. 2024 Dec 9;12(12):2537.
doi: 10.3390/microorganisms12122537.

Effects of the Symbiotic Chlorella variabilis on the Host Ciliate Paramecium bursaria Phenotypes

Affiliations
Review

Effects of the Symbiotic Chlorella variabilis on the Host Ciliate Paramecium bursaria Phenotypes

Yuuki Kodama et al. Microorganisms. .

Abstract

Paramecium bursaria, a ciliated protist, forms a symbiotic relationship with the green alga Chlorella variabilis. This endosymbiotic association is a model system for studying the establishment of secondary symbiosis and interactions between the symbiont and its host organisms. Symbiotic algae reside in specialized compartments called perialgal vacuoles (PVs) within the host cytoplasm, which protect them from digestion by host lysosomal fusion. The relationship between P. bursaria and symbiotic Chlorella spp. is characterized by mutualism, in which both organisms benefit from this association. Furthermore, symbiotic algae also influence their host phenotypes, and algae-free P. bursaria can be obtained through various methods and reassociated with symbiotic algae, making it a valuable tool for studying secondary endosymbiosis. Recent advancements in genomic and transcriptomic studies on both hosts and symbionts have further enhanced the utility of this model system. This review summarizes the infection process of the symbiotic alga C. variabilis and its effects on the algal infection on number of host trichocysts, mitochondria, cytoplasmic crystals, total protein amount, stress responses, photoaccumulation, and circadian rhythms of the host P. bursaria.

Keywords: Chlorella sp.; Chlorella variabilis; Paramecium bursaria; cytoplasmic crystal; digestive vacuole; endosymbiosis; heat tolerance; mitochondria; perialgal vacuole; photoaccumulation; trichocyst.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Differential interference contrast (DIC) micrographs of P. bursaria, a model organism for investigating the induction of secondary symbiosis. (A) P. bursaria harboring several hundred symbiotic C. variabilis. (B) Artificial algae-removed P. bursaria from (A). (C) Shows (B) fixed 30 s after mixing with the symbiotic C. variabilis isolated from (A). The upper and lower sides of the photographs are the anterior and posterior sides, respectively. Cy, cytopharynx; Ma, macronucleus; d, digestive vacuole (DV)-containing algae. Kodama, unpublished micrographs.
Figure 2
Figure 2
DIC micrographs of the re-endosymbiosis process of symbiotic C. variabilis to algae-free P. bursaria. (A) DV-IIIb was observed 19 min after mixing algae-free P. bursaria and symbiotic C. variabilis isolated from algae-bearing cells. Digested faint yellow algae (white arrowhead) and undigested green algae (arrow) coexisted in the same DV. (B) Several DV-IVbs were detected within 30 min of mixing with algae-free P. bursaria and the isolated symbiotic Chlorella sp. Digested brownish algae (white arrowhead) and undigested green algae (arrow) coexisted in the same DV. (C) Large DV (d) containing a large number of algae observed 1 h after mixing with algae-free P. bursaria and isolated symbiotic Chlorella sp. Green (arrow) and brownish (white arrowhead) algae budded from the DV one cell at a time. (D) Single green algae adhering below the host Paramecium cortex (arrow) observed 3 h after mixing with algae-free P. bursaria and the isolated symbiotic Chlorella sp. Ma, macronucleus; d, DV. Kodama, unpublished micrographs.
Figure 3
Figure 3
This diagram shows the fate of algae-free P. bursaria after ingestion of (A) free-living Chlorella sorokiniana strain NIES-2169, (B) native Chlorella variabilis strain 1N isolated from algae-bearing P. bursaria, (C) a mixture of NIES-2169 and 1N, and (D) pathogenic bacteria F. novicida strain U112. The blue line represents the PV membrane. The figure was taken from [69] with permission. The color of the PV membrane has changed from blue in the original figure to red.
Figure 4
Figure 4
(A) DIC micrographs of algae-free P. bursaria (left), algae-bearing P. bursaria (middle), and P. multimicronucleatum (right). Cy, cytopharynx; Ma, macronucleus. (B) Highlight the presence of crystals, with increased brightness, to make them more visible. In particular, the posterior end of algae-free P. bursaria contained numerous glowing crystals (left), whereas the algae-bearing P. bursaria exhibited relatively small crystals (middle). Additionally, a few less bright crystals were present in P. multimicronucleatum, as indicated by the white arrow (right). The figure was obtained from [78] and licensed under CC-BY-4.0 International.
Figure 5
Figure 5
(A) Transmission electron micrographs of symbiotic alga below the host cell cortex. The PV membrane (PVm) enclosing the symbiotic alga (a) and the host mitochondria (mt) are in close contact (arrowhead), and the trichocyst membrane (tcm) enclosing the trichocyst (tc) is also present near the PV membrane. The upper parts of the transmission electron micrographs show the cell surface of P. bursaria. bb shows the basal body of the host cilia. (B,C) Transmission electron micrographs of the host trichocyst (B) and mitochondrion (C). Kodama, unpublished micrographs.
Figure 6
Figure 6
Production of mAbs and experimental flowchart. Mass cultures of algae-bearing P. bursaria in the early stationary phase of growth were harvested, and the sedimented cells were homogenized. The homogenate was injected intraperitoneally into 8-week-old BALB/c mice. For hybridoma cell cloning, culture supernatants were screened using indirect IF microscopy [82], and mAbs specific for trichocysts or mitochondria of P. bursaria have been developed. Differences in the number and arrangement of host trichocysts and mitochondria before and after algal symbiosis were examined by indirect IF microscopy. This figure was prepared with reference to [61,81].
Figure 7
Figure 7
Photomicrographs of algae-free P. bursaria during algal reinfection and changes in the number and arrangement of host trichocysts. The images (A,C,E,G,I,K,M) are shown as DIC images, and the images (B,D,F,H,J,L,N) as IF images. (I,J) are enlarged images of upper parts of (G,H). Green fluorescence (that is, IF) indicates the presence of host trichocysts. IF was observed throughout the cells before mixing with the algae (B). Thirty minutes after mixing, one of the algae exhibited temporary resistance to host lysosomal enzymes and remained intact in the DV ((E), arrowhead). Indirect IF microscopy revealed no alterations in the trichocysts (F). Three hours post-mixing, green algae that had escaped from the host DVs were observed to localize below the host Paramecium cortex ((G); arrows). Trichocysts reorganized into a ring-like formation surrounding the symbiotic algae (arrowhead and double arrowhead in (J)). Twenty-four hours after mixing, algae proliferated through cell division, establishing endosymbiosis (K). Ring-shaped trichocysts increased concomitantly with algae below the host Paramecium cortex (L). Forty-eight hours after mixing, some algae-free P. bursaria cells did not establish endosymbiosis with the isolated symbiotic algae (M), and the IF pattern of the trichocysts resembled that observed under pre-mixing conditions (N). Ma, macronucleus. The figure was taken from [61] with permission.
Figure 8
Figure 8
DIC and indirect IF photomicrographs of symbiotic algae-free and algae-bearing P. bursaria labeled with a mAb specific for Paramecium mitochondria. (A,B,B’): algae-free P. bursaria. (C), (D,E,E’): algae-bearing P. bursaria. (A,C): DIC photomicrographs. (B–E,E’): indirect IF micrographs. Small granules with green fluorescence indicate the host mitochondria. Large particles with red fluorescence show autofluorescence of chlorophyll in algal chloroplasts. (B’): an enlarged view of the host cortex in (B). (E): a merge of (D) and the autofluorescence of chlorophyll. (E’): enlarged view of (E), in which several symbiotic algae are surrounded by host mitochondria. It should be noted that the mitochondria near the cell cortex in algae-free cells (B’) were more abundant than those in algae-bearing cells (E’). Ma, macronucleus. Scale bars for (A–E) represent 20 μm, and those for (B’,E’) represent 5 μm. (F): IF intensity of mitochondria in algae-free and algae-bearing P. bursaria. In algae-free P. bursaria (gray bar graph), the IF intensity was higher than that in algae-bearing P. bursaria cells (green bar graph). Error bars represent standard deviation (SD). Asterisks denote significant differences (two-sided Fisher’s exact test; *** p < 0.001). These photomicrographs and a graph were obtained from [81] and licensed under CC-BY-4.0 International.
Figure 9
Figure 9
(A) Schematic representation of the algal reinfection. Four important cytological events (labeled 1–4) are required to establish endosymbiosis [51]. 1. Approximately 3 min after mixing algae-free P. bursaria cells with isolated symbiotic algae, some algae in the DVs acquire resistance to host lysosomal enzymes. 2. Approximately 30 min after mixing, algae escape from the DVs by budding the DV membrane. This budding is completely inhibited by the dynamin inhibitor Dynasore. 3. Approximately 45 min after mixing, the DV membrane enclosing a single undigested green alga differentiates into the PV membrane (red), which provides protection from host lysosomal fusion. 4. The alga localizes beneath the host cell cortex by the adhesion of the PV membrane to the host mitochondrial outer membrane and pushing aside host trichocysts. Approximately 24 h after mixing, the alga beneath the host cell cortex begins cell division and establishes endosymbiosis (updated from [112] with permission). (B) Host changes associated with algal symbiosis. References numbers are as follows. Kodama et al. 2024 [78]; Kodama and Fujishima 2009 [57]; Kodama and Fujishima 2011 [61]; Morita and Kodama 2024 [85]; Kodama and Fujishima 2022 [81]; Hörtnagl and Sommaruga 2007 [23]; Iwatsuki et al. 1998 [104]; Miwa 2009 [24]; Summerer et al. 2009 [25]; Kodama et al., 2014 [42].

References

    1. Bodył A., Mackiewicz P., Ciesála J. Reference Module in Life Sciences. Elsevier; Amsterdam, The Netherlands: 2017. Endosymbiotic Theory: Models and Challenges.
    1. Leung T.L.F., Poulin R. Parasitism, commensalism, and mutualism: Exploring the many shades of Symbioses. Vie Milieu/Life Environ. 2008;58:107–115.
    1. Davy S.K., Allemand D., Weis V.M. Cell Biology of Cnidarian-Dinoflagellate Symbiosis. Microbiol. Mol. Biol. Rev. 2012;76:229–261. doi: 10.1128/MMBR.05014-11. - DOI - PMC - PubMed
    1. Goetsch W. Die symbiose der süsswasser-hydroiden und ihre künstliche beeinflussung. Z. Morph Okol. Tiere. 1924;1:660–751. doi: 10.1007/BF00407607. - DOI
    1. Lee J.J., Soldo A.T., Reisser W., Lee M.J., Jeon K.W., Görtz H.-D. The Extent of Algal and Bacterial Endosymbioses in Protozoa. J. Protozool. 1985;32:391–403. doi: 10.1111/j.1550-7408.1985.tb04034.x. - DOI
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