科研之友
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摘要
Twenty nine Phormidium-like strains, obtained from different culture collections, isolated from different habitats and geographical localities were analyzed morphologically as well as using HPLC, spectrophotometry, RAPD markers (random amplified polymorphic DNA) and RFLP (restriction fragment length polymorphism) of 16S rRNA sequences. On the base of cell width, degree of constriction between adjacent cells and cell form three distinct groups were recognized. Group 1 consisted of strains with the cell width less than 1.5 mu m, elongated with strong constrictions; group II contained majority strains with the cell width between 1.5 and 2.5 mu m, isodiametric and only slight constrictions and the cross walls; group III contained strains with cells more than 2.5 mu m wide and disc shaped, without constrictions. In strains investigated here, only eight major carotenoids and three mycosporines occurred. Phormidium-like strains showed remarkable differences in the carotenoid composition. Four main combinations in occurrence of different carotenoids were found. The presence of zeaxanthin and beta-carotene was common to all studied strains. Molecular analysis did not show any correlation between pigment composition of strains and their phylogenetic relationship. However, genetically similar strains were similar in cell size and shape. The observed morphotypic traits by themselves appear to be insufficient for classification because some distant groups also showed similar features. Our results support the notion that the genus Phormidium sensu Gomont represents a phylogenetically polyphyletic group. Furthermore, our data have demonstrated the need for a comprehensive revision of the taxonomy of this group. Results of our studies show that the taxonomic problems of the filamentous cyanobacteria with narrow trichomes can be solved only with the application of modern, combined criteria.
- 出版日期2011-7
