MORPHOLOGY OF DNA CONTAINING STRUCTURES (NUCLEOIDS) AS A PROSPECTIVE CHARACTER IN CYANOPHYTE TAXONOMY

DNA containing structures (nucleoids) were visualized by 4'6-diamidino -2-phenylindole (DAPI) fluorescent staining in two groups of cyanophyt es (59 filamentous oscillatorialean species and 12 coccal Synechococcu s-like organisms) to test the possibility of using nucleoid morphology in cyanophyte taxonomy. The morphology of nucleoids (size, shape, and structure) in oscillatorialean species is specific for individual fam ilies. The morphology of the nucleoid in Synechococus-like species agr ees with the proposed separation of the genus Cyanothece from Synechoc occus. A much different nucleoid morphology in three species of Cyanot hece suggests that these species should be separated into a new genus. On the basis of other characters, the species could be returned to th e genus Cyanobacterium. My results indicate that the morphology of nuc leoids is a valuable character in the classification of the cyanophyte s examined; thus, it is a prospective feature that could be used in th e taxonomy of other groups of cyanophytes. Additionally, DAPI staining is not a complicated procedure. The new character is easy to see in s amples taken from nature, both living and preserved.