Archives of Microbiology

, Volume 130, Issue 2, pp 165–174 | Cite as

Ultrastructure of a cave-wall cyanophyte-Gloeocapsa NS4

  • Guy Cox
  • Diana Benson
  • D. M. Dwarte


Gloeocapsa strain NS4, a cyanophyte (cyanobacterium) which grows in low light levels inside cave entrances, was studied in the electron microscope by thin sectioning and freeze-etching. The cells are surrounded by a microfibrillar sheath divided by ‘dense lamellae’, which are probably an acidic mucopolysaccharide. Inside this is a typical Gramnegative cell wall. Double-replica freeze-fracture showed that the outer envelope of the wall fractures to give two faces each consisting of densely-packed particles; the particles of the outer leaflet seem to consist of subunits arranged in a hollow cylinder. A structural model of the outer envelope is proposed. The plasma membrane fractures to give a PF face with 3000 ∼ 9 nm particles μm-1 and an EF face with 150–700 11–12 nm particles μm-1. The thylakoids are arranged in a pattern not previously found in a unicellular cyanophyte, parallel arrays which intersect, and may fuse with, the plasma membrane. The thylakoid membranes have 2,850 particles μm-1, mean size 10.9 nm, on the PF face and 560 particles μm-1, mean size 12.3 nm, on the EF face. Phycobilisomes are difficult to see, but may be unusually large. These ultrastructural features may be adaptations to a very low light habitat.

Key words

Gloeocapsa Cyanophyte Cyanobacterium Freeze-etch Gram-negative cell wall Sheath Thylakoid Phycobilisome 


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Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • Guy Cox
    • 1
  • Diana Benson
    • 1
  • D. M. Dwarte
    • 1
  1. 1.Electron Microscope UnitUniversity of SydneyAustralia

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