, Volume 182, Issue 3, pp 126–148

Biochemistry and structure of the glycan secreted by desiccation-tolerantNostoc commune (Cyanobacteria)

  • Donna R. Hill
  • A. Peat
  • M. Potts

DOI: 10.1007/BF01403474

Cite this article as:
Hill, D.R., Peat, A. & Potts, M. Protoplasma (1994) 182: 126. doi:10.1007/BF01403474


Filaments of the desiccation-tolerant cyanobacteriumNostoc commune are embedded within, and distributed throughout, a dense glycan sheath. Analysis of the glycan of field materials and of pure cultures ofN. commune DRH 1 through light and electron microscopy, immunogold labelling and staining with dyes, revealed changes in the pattern of differentiation in glycan micro-structure, as well as localized shifts in pH, upon rehydration of desiccated field material. A Ca/Si rich external (pellicular) layer of the glycan acts as a physical barrier to epiphytic bacteria on the surface ofN. commune colonies. A purified fraction (>12 kDa) of an aqueous extract of the glycan from desiccated field material contained glucose, N-acetylglucosamine, glucosamine, mannose, and galactosamine with ratios of 3.1∶1.4∶1∶0.1∶0.06, respectively. Lipid soluble extracts ofN. commune contained trehalose and sucrose and the levels of both became undetectable following cell rehydration. Intracellular cyanobacterial trehalase was identified using immunoblotting and its synthesis was detected upon rehydration of desiccated field cultures. Elemental analysis of glycan extracts showed a flux in the concentrations of salts in the glycan matrix following rehydration of desiccated colonies. Water-stress proteins (Wsp; most abundant proteins in glycan), a water soluble UV-A/B-absorbing pigment, the lipid-soluble UV-protective pigment scytonemin (in both its oxidized and reduced forms), as well as two unidentified cyanobacterial glycoproteins (75 kDa and 110 kDa), were found within the glycan matrix. An unidentified 68 kDa protein, the second most abundant protein in aqueous extracts of the glycan, was isolated and its N-terminal sequence was determined as AFIFGTISPNNLSGTSGNSGIVGSA. Gene bank searches with this sequence identified significant homologies (35–45%) with various carbohydrate-modifying enzymes. The role of the glycan in the desiccation tolerance ofN. commune is discussed with respect to structure/function relationships.


UV-absorbing pigmentsProtein secretionCapsuleGlycoproteinsTrehalose



extracellular polysaccharides


water-stress protein


scanning electron microscopy


transmission electron microscopy


energy dispersive X-ray analysis


fast performance liquid chromatography


sodium dodecylsulfate polyacrylamide gel electrophoresis


thin layer chromatography


ultra-violet radiation


University of Texas Culture Collection

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • Donna R. Hill
    • 1
  • A. Peat
    • 1
  • M. Potts
    • 1
  1. 1.Department of BiochemistryVirginia Polytechnic Institute and State UniversityBlacksburgUSA
  2. 2.PhylaroqueFrance