The Phylogenetics Relationships Of The Genus Paramecium Inferred From Small Subunit RRNA Gene Sequences And Comparison Of Morphology In P.bursaria-Chlorella System

The silverline system and the distribution of symbiotic Chlorella of Chlorella -containing P.bursaria and Chlorella-free P.bursaria were determined by use of scanning electron microscopy, FLUTAX; The phylogenetic relationships and molecular genetic characters within the Paramecium clade were also studied by CLUSTALW , MEGA2.0 and PAUP, especially those characters between Chlorella-contaming P.bursaria and Chlorella-free P.bursaria. As an out-group, Tetrahymena thermophila was selected. The result is as follows: 1 Comparison of morphology in P.bursaria -Chlorella systemWith scanning electron microscopy, the study shows that Chlorella often distribute in the posterior of Paramecium, and the number of Chlorella is depended on the nutritional state of P.bursaria. The disappearance of Chlorella is always from the anterior to the posterior of Paramecium while distributed in both of poles when cell comes into asexual reproduction. Therefore the author speculates that the distribution of Chlorella is not randomly but related with the cell polarity.The results inferred from scanning electron microscopy show the data of silverline system in the following area: adoral zone and anoral zone. In anterior adoral zone, the gridding in Chlorella-containing P.bursaria was 2.Hum long and 1.5um wide; the distance of longitudinal cilia was 2um as same as that in latitude cilia; the gridding in Chlorella-free P.bursaria was 1.4um long and lum wide, the distance of longitudinal cilia was 2um while that of latitude cilia was lum; in posterior adoral zone, the gridding in Chlorella-containing P.bursaria was 2um long and 0.95um wide, the distance of longitudinal cilia was 2um and that of latitude cilia was 0.95um; the gridding in Chlorella-free P.bursaria was 2.2um long and 1.8um wide, the distance of longitudinal cilia was 1.8um as same as that of latitude cilia; in anoral zone, the gridding in Chlorella-containing P.bursaria was 4um long and 3.2um wide, the distance of longitudinal cilia was5um as same as that of latitude cilia; the gridding in Chlorella-free P.bursaria was 4um long and 3.6um wide, the distances of longitudinal cilia and of latitude cilia were 4um. In light microscopy, the size of Chlorella -containing P.bursaria is bigger than Chlorella-free P.bursaria. As a consequence, the gridding of silverline system in Chlorella-free P.bursaria is also bigger. Hereby it is supposed that the differences of cell size in Paramecium-Chlorella system is the result of interaction between symbiotic Chlorella and the host, which is capable of affecting the cilia mobility.2 Phylogenetics relations in Genus ParameciumTo confirm the difference of SSUrRNA gene in Chlorella -containing Pbursaria and Chlorella-free Pbursaria and to resolve relationships within the genus, small subunit rRNA gene sequences of 13 kinds of Paramecium were determined and aligned. The nucleotide composition, locations in codon, distance, standard error, transitional and transversional rate of SSUrRNA gene within the Paramecium clade were determined using the method of Kimura two-parameter correction model; the phylogenetic tree was constructed using the neighbor-joining method (NJ), maximum-parsimony method (MP) as well as maximum-likelihood method (ML). The results suggest that: (1) there is not any difference of SSUrRNA gene between Chlorella-containing Pbursaria and Chlorella-free Pbursaria, indicating the symbiotic Chlorella, as an environment factor, cannot affect the conserved gene of host such as SSUrRNA gene; in genus Paramecium, the content of nucleotide is A>T (U)>G>C, and there are 1258 conserved positions, 361 variable positions. Average identical pairs are 1473, transitional pairs are 62 and transvertional pairs are 64. Si/Sv is 1. The distance between Chlorella -containing Pbursaria and Chlorella-free Pbursaria is 0.01, which is the smallest; while P.caudatum gets the biggest distance: ranging from 0.156-0.164. The average distance is 0.084. (2) All analyses (neighbor-joining [NJ], maximum-parsimony [MP], and maximum-likelihood [ML]) and the constructed trees...