Original paper

Structural and ultrastructural characterization of Symploca atlantica Gomont, strain PCC 8002 (Oscillatoriales, Cyanophyta, Cyanobacteria)

Porta, David; Hernández-Mariné, Mariona; Herdman, Michael; Rippka, Rosmarie


The genus Symploca Kütz. ex Gom. was orginally described for cyanobacteria from terrestrial humid habitats that exhibit anastomosed prostrate filaments and form erect bundles. However, species from marine environments are also known and have been assigned to Symploca atlantica Gomont 1892 or Symploca funicularis Setchell et Gardner 1918. In this communication, the structural and ultrastructural features of the axenic strain PCC 8002, conforming to S. funicularis, are described. The individual trichomes of this filamentous non-heterocystous cyanobacterium are covered by a multilayered fibrous sheath and some filaments are enclosed within a common supplementary layer of sheath material. Photosynthetic pigments are mainly located at the periphery of the cells. Reproduction occurs by a symmetric binary fission, in which a new septum is only initiated after complete formation of a previous crosswall ("discontinuous cell division"); trichome breakage involves necridium formation, the cells adjacent ecridia subsequently developing into the morphologically distinct, apical cells. Several parallel rows of junctional pores could be observed between the longitudinal cell wall and the cross walls. SYTOX Green staining revealed compact nucleoids, whose partitioning accompanied cellular division. A comparison between this strain and the previously described Symploca strain IUCC B 617 (Pankratz & Bowen 1963, Baker & Bold 1970) is provided. The relationship with Microcoleus chthonoplastes is discussed.


confocal microscopynucleoidsytox greentransmission electron microscopyultrastructurephylogeny