The green ciliate, Paramecium bursaria, has evolved a mutualistic relationship with endosymbiotic green algae (photobionts). Under culture conditions, photobionts are usually unified (to be single species) within each...The green ciliate, Paramecium bursaria, has evolved a mutualistic relationship with endosymbiotic green algae (photobionts). Under culture conditions, photobionts are usually unified (to be single species) within each P. bursaria strain. In most cases, the algal partners are restricted to either Chlorella variabilis or Micractinium reisseri (Chlorellaceae, Trebouxiophyceae). Both species are characterized by particular physiology and atypical group I intron insertions, although they are morphologically indistinguishable from each other or from other Chlorella-related species. Both algae are exclusive species that are viable only within P. bursaria cells, and therefore their symbiotic relationship can be considered persistent. In a few cases, the other algal species have been reported as P. bursaria photobionts. Namely, P. bursaria have occasionally replaced their photobiont partner. This paper introduces some P. bursaria strains that maintain more than one species of algae for a long period. This situation prompts speculations about flexibility of host-photo-biont relationships, how P. bursaria replaced these photobionts, and the infection theory of the group I introns.展开更多
The lichen species Usnea aurantiaco-atra （Jacq.） Bory is the most dominant vegetation on the Fildes Peninsula, Antarctica. Most individuals grow on rocks, and some are found with mosses. During the 27th and 28th Chi...The lichen species Usnea aurantiaco-atra （Jacq.） Bory is the most dominant vegetation on the Fildes Peninsula, Antarctica. Most individuals grow on rocks, and some are found with mosses. During the 27th and 28th Chinese National Antarctic Research expeditions of the Great Wall Station, U. aurantiaco-atra was observed growing on the lichen thallus of Umbilicaria antarctica Frey ＆ I.M. Lamb, or on wood, which indicated that Usnea aurantiaco-atra could grow on various substrates. The diversities of the symbionts in U. aurantiaco-atra collected in the Fildes Peninsula were investigated using ITS rDNA sequences. The results showed that the sequences from mycobionts of U. aurantiaco-atra growing on various substrates did not exhibit significant differences. All photobionts in this lichen species were the green algae Trebouxia jamesii （Hildreth ＆ Ahmadjian） Gartner. The identical sequences from the photobionts of both Umbilicaria antarctica and Usnea aurantiaco-atra indicated there was an algae pool in this area and different mycobionts could obtain their algal partners from this pool. The variety of substrates for U. aurantiaco-atra suggested its photobiont could be obtained from a mature lichen thallus by vegetative propagation; from other lichen thalli （e.g. Umbilicaria antarctica）; or from the surroundings. This study will promote understanding of the distribution of photobionts and the process of lichenization.展开更多
The article presents information about the taxonomy and ecology of lichens in the Ohaliksai River basin. According to the conducted studies, 11 families <span>of the Lecanoromycetes class (Parmeliaceae, </spa...The article presents information about the taxonomy and ecology of lichens in the Ohaliksai River basin. According to the conducted studies, 11 families <span>of the Lecanoromycetes class (Parmeliaceae, </span></span><span style="font-size:10.0pt;font-family:"">Lecanoraceae</span><span style="font-size:10.0pt;font-family:"">, Ramalinaceae, M</span><span style="font-size:10.0pt;font-family:"">e<span>gasporaceae, Physciaceae, Teloschistaceae, Peltigeraceae, Collemataceae, Ca</span>n<span>delariaceae, Umbilicariaceae, Physciaceae), 1 family of the Eurotiomycetes cla</span>ss (Verrucariaceae) and 1 family Lichinaceae of the class Lichinomycetes were identified, 18 groups and 23 species were noted as widespread. The taxonomic<span> analysis and ecological characteristics of the identified specie</span>s are presented.展开更多
文摘The green ciliate, Paramecium bursaria, has evolved a mutualistic relationship with endosymbiotic green algae (photobionts). Under culture conditions, photobionts are usually unified (to be single species) within each P. bursaria strain. In most cases, the algal partners are restricted to either Chlorella variabilis or Micractinium reisseri (Chlorellaceae, Trebouxiophyceae). Both species are characterized by particular physiology and atypical group I intron insertions, although they are morphologically indistinguishable from each other or from other Chlorella-related species. Both algae are exclusive species that are viable only within P. bursaria cells, and therefore their symbiotic relationship can be considered persistent. In a few cases, the other algal species have been reported as P. bursaria photobionts. Namely, P. bursaria have occasionally replaced their photobiont partner. This paper introduces some P. bursaria strains that maintain more than one species of algae for a long period. This situation prompts speculations about flexibility of host-photo-biont relationships, how P. bursaria replaced these photobionts, and the infection theory of the group I introns.
基金supported by State Oceanic Administration, P. R. China (Grant nos. 10/11 GW06, 2011GW12016)the National Natural Science Foundation of China (Grant nos. 31000010, 31270118, 41206189)
文摘The lichen species Usnea aurantiaco-atra （Jacq.） Bory is the most dominant vegetation on the Fildes Peninsula, Antarctica. Most individuals grow on rocks, and some are found with mosses. During the 27th and 28th Chinese National Antarctic Research expeditions of the Great Wall Station, U. aurantiaco-atra was observed growing on the lichen thallus of Umbilicaria antarctica Frey ＆ I.M. Lamb, or on wood, which indicated that Usnea aurantiaco-atra could grow on various substrates. The diversities of the symbionts in U. aurantiaco-atra collected in the Fildes Peninsula were investigated using ITS rDNA sequences. The results showed that the sequences from mycobionts of U. aurantiaco-atra growing on various substrates did not exhibit significant differences. All photobionts in this lichen species were the green algae Trebouxia jamesii （Hildreth ＆ Ahmadjian） Gartner. The identical sequences from the photobionts of both Umbilicaria antarctica and Usnea aurantiaco-atra indicated there was an algae pool in this area and different mycobionts could obtain their algal partners from this pool. The variety of substrates for U. aurantiaco-atra suggested its photobiont could be obtained from a mature lichen thallus by vegetative propagation; from other lichen thalli （e.g. Umbilicaria antarctica）; or from the surroundings. This study will promote understanding of the distribution of photobionts and the process of lichenization.
文摘The article presents information about the taxonomy and ecology of lichens in the Ohaliksai River basin. According to the conducted studies, 11 families <span>of the Lecanoromycetes class (Parmeliaceae, </span></span><span style="font-size:10.0pt;font-family:"">Lecanoraceae</span><span style="font-size:10.0pt;font-family:"">, Ramalinaceae, M</span><span style="font-size:10.0pt;font-family:"">e<span>gasporaceae, Physciaceae, Teloschistaceae, Peltigeraceae, Collemataceae, Ca</span>n<span>delariaceae, Umbilicariaceae, Physciaceae), 1 family of the Eurotiomycetes cla</span>ss (Verrucariaceae) and 1 family Lichinaceae of the class Lichinomycetes were identified, 18 groups and 23 species were noted as widespread. The taxonomic<span> analysis and ecological characteristics of the identified specie</span>s are presented.
