Isolation and chemical characterization of the sheath from the cyanobacterium Chroococcus minutus SAG B.41.79

1 Institut für Biologie II, Mikrobiologie, der Albert-Ludwigs-Universität, Schänzlestr. 1, D-7800 Freiburg i.Br., Federal Republic of Germany 2 Max-Planck-Institut für Immunbiologie, Stübeweg 51, D-7800 Freiburg i.Br., Federal Republic of Germany ABSTRACT SUMMARY: The sheath of the unicellular cyanobacterium Chroococcus minutus SAG B.41.79 was isolated from a crude cell envelope fraction by discontinuous sucrose gradient centrifugation, and was further purified by treatment with lysozyme followed by Triton X-100 or sodium dodecyl sulphate (SDS) extraction. The absence of muramic and diaminopimelic acids and of β-hydroxy fatty acid showed the fraction to be free from cell wall components. The sheath had a fibrillar fine structure with the fibres parallel to the cell surface. The total neutral sugar content was 45.9% (w/w). The main sugars were glucose and 2- O -methyl-6-deoxyhexose. Additional O -methyl sugars, 2- O -methylhexose, 3- O -methylhexose and a 2- O -methyl sugar (not further identified), were present. Protein could not be completely removed from the sheath fraction by treatment with boiling SDS. The contents of fatty acids, phosphorus, uronic acids and glucosamine in the fraction were all less than 0.5% (w/w). Present address: Dharanidhar College, 758001-Keonjhar, Orissa, India.