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Morphological diversity and molecular phylogeny of five Paramecium bursaria (Alveolata, Ciliophora, Oligohymenophorea) syngens and the identification of their green algal endosymbionts
Date Issued
2022
Author(s)
DOI
10.1038/s41598-022-22284-z
Abstract
Abstract
Paramecium bursaria
is a mixotrophic ciliate species, which is common in stagnant and slow-flowing, nutrient-rich waters. It is usually found living in symbiosis with
zoochlorellae
(green algae) of the genera
Chlorella
or
Micractinium
. We investigated
P. bursaria
isolates from around the world, some of which have already been extensively studied in various laboratories, but whose morphological and genetic identity has not yet been completely clarified. Phylogenetic analyses of the SSU and ITS rDNA sequences revealed five highly supported lineages, which corresponded to the syngen and most likely to the biological species assignment. These syngens R1–R5 could also be distinguished by unique synapomorphies in the secondary structures of the SSU and the ITS. Considering these synapomorphies, we could clearly assign the existing GenBank entries of
P. bursaria
to specific syngens. In addition, we discovered synapomorphies at amino acids of the COI gene for the identification of the syngens. Using the metadata of these entries, most syngens showed a worldwide distribution, however, the syngens R1 and R5 were only found in Europe. From morphology, the syngens did not show any significant deviations. The investigated strains had either
Chlorella variabilis
,
Chlorella vulgaris
or
Micractinium conductrix
as endosymbionts.
Paramecium bursaria
is a mixotrophic ciliate species, which is common in stagnant and slow-flowing, nutrient-rich waters. It is usually found living in symbiosis with
zoochlorellae
(green algae) of the genera
Chlorella
or
Micractinium
. We investigated
P. bursaria
isolates from around the world, some of which have already been extensively studied in various laboratories, but whose morphological and genetic identity has not yet been completely clarified. Phylogenetic analyses of the SSU and ITS rDNA sequences revealed five highly supported lineages, which corresponded to the syngen and most likely to the biological species assignment. These syngens R1–R5 could also be distinguished by unique synapomorphies in the secondary structures of the SSU and the ITS. Considering these synapomorphies, we could clearly assign the existing GenBank entries of
P. bursaria
to specific syngens. In addition, we discovered synapomorphies at amino acids of the COI gene for the identification of the syngens. Using the metadata of these entries, most syngens showed a worldwide distribution, however, the syngens R1 and R5 were only found in Europe. From morphology, the syngens did not show any significant deviations. The investigated strains had either
Chlorella variabilis
,
Chlorella vulgaris
or
Micractinium conductrix
as endosymbionts.
