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(Nostoc) and its related genera Nostoc are important groups of cyanobacteria, widely distributed in a variety of habitats. Their classification is mainly built on the basis of the morphological characteristics of the filaments, vegetative cells, heterocyst and thick-walled spores, however, the simple structure of these algae, morphological plasticity, easily influenced by the environment, and therefore, as a classification based on morphological characteristics only sometimes unreliable, likely to cause confusion in the classification. With the development of molecular systematics, a growing number of nucleotide and protein sequences in the system evolution and classification study provides the most direct evidence, has been widely used for the study of cyanobacteria molecular phylogeny. This study by cloning, sequencing, has a the \Nostoc and Its Allied Phylogenetic relationship analysis, the main results are as follows: [1] based on the 16S rRNA gene and tRNA Leu (UAA) intron gene phylogenetic results that Nostoc (Nostoc) and Anabaena (Anabaena) aggregated into two different branches, and to support them as two separate genera. [2] based on the 16S rRNA gene and tRNA Leu (UAA) intron gene sequences in the evolutionary tree, the topology is basically the same genus Nostoc, the vast majority of Nostoc polymerization in a monophyletic branch, indicating that they are monophyletic origin. [3] However, phylogenetic studies show that a small number of Nostoc (of Nostoc paludosum FACHB88 the Nostoc spongiaeforme FACHB130 the Nostoc piscinale CENA21 Nostoc sp At FACHB973 Nostoc sp. YK-01 and Nostoc sp HK-01) were excluded from this single outside the Department, with a small number of several strains of Anabaena clustering into a branch, this branch a monophyletic clade located Nostoc and Anabaena branch with clear boundaries between, and the genetic distance between them than the genus within the level, do not support the existing taxonomic status. This indicates the type of the branch may transition between the two genera groups, or for a new group to be studied further. [4] In this study show that the Azolla Anabaena (Anabaena azollae FACHB190) the taxonomic status of the disputed exist in the branch, neither clustering Nostoc genus monophyletic clade, nor clustering in typical fish fishy algal genus branch support Azolla Anabaena view independent of the outside of the two genera. [5] The study found Aphanizomenon algae (Aphanizomenon) always mixed and Anabaena clustered together, and the genetic distance between Anabaena, Aphanizomenon algae genus Anabaena incorporated into the case . [6] The results show the filamentous cyanobacteria clustering with heterocyst a monophyletic clade, indicating that they are monophyletic origin. [7] 16S rRNA gene and tRNA Leu (UAA) intron gene combined results of phylogenetic analysis showed that the three kinds of economic Nostoc - General Nostoc (N. commun), hairy of of Nostoc the (N. flagelliforme) and the proposed spherical of Nostoc the (N. sphaeroids) should the three separate species, which, especially closer genetic relationship between the ordinary Nostoc Nostoc algae. Nostoc and Its Allied Phylogenetic relationship analysis, and evaluation of their classification status was discussed, with a focus on species classification controversial, and according to the results of these species the taxonomic status of the proposed amendments.
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