TY - JOUR
T1 - The cell surface glycoprotein layer of the extreme halophile Halobacterium salinarum and its relation to Haloferax volcanii
T2 - Cryo-electron tomography of freeze-substituted cells and projection studies of negatively stained envelopes
AU - Trachtenberg, Shlomo
AU - Pinnick, Baruch
AU - Kessel, Martin
PY - 2000/5
Y1 - 2000/5
N2 - We have studied the surface layer (S-layer) of Halobacterium salinarum (formerly Halobacterium halobium), an extreme halophile requiring high concentrations of sodium, by electron microscopy of (a) isolated, negatively stained, flattened envelopes and (b) cryo-fixation of intact cells in their high-salt growth medium followed by freeze substitution and tomography of thin sections. From the negatively stained isolated envelopes we have calculated a two-dimensional, projection map that is strikingly similar to that of Haloferax volcanii, an extreme halophile requiring high concentrations of magnesium; both projection maps show the hexagonal arrangement of the morphological units with an identical center-to-center spacing of 156 Å; each of the morphological units of the two species has six subunits with a similar density distribution and apparent domain organization. In contrast to the two-dimensional map, the tomographic reconstruction of Halob. salinarum does not agree in a straight-forward way with the three-dimensional, electron crystallographic map of negatively stained Halof. volcanii envelopes, although the main features of the lattice and the morphological units are evident. The tomographic reconstruction of sections from epoxy-embedded material suffers from directional compression due to sectioning stress and continuous dimensional changes and mass loss due to electron irradiation. This communication consists, therefore, of three parts: (a) a comparison of the projection maps of negatively stained envelopes of Halof. volcanii and Halob. salinarum; (b) a comparison of the three-dimensional maps obtained by electron crystallography (Halof. volcanii) and low-dose cryotomography (Halob. salinarum); and (c) a methodological study of mass loss and dimensional changes of plastic-embedded material under low-dose conditions at room and liquid nitrogen temperatures. (C) 2000 Academic Press.
AB - We have studied the surface layer (S-layer) of Halobacterium salinarum (formerly Halobacterium halobium), an extreme halophile requiring high concentrations of sodium, by electron microscopy of (a) isolated, negatively stained, flattened envelopes and (b) cryo-fixation of intact cells in their high-salt growth medium followed by freeze substitution and tomography of thin sections. From the negatively stained isolated envelopes we have calculated a two-dimensional, projection map that is strikingly similar to that of Haloferax volcanii, an extreme halophile requiring high concentrations of magnesium; both projection maps show the hexagonal arrangement of the morphological units with an identical center-to-center spacing of 156 Å; each of the morphological units of the two species has six subunits with a similar density distribution and apparent domain organization. In contrast to the two-dimensional map, the tomographic reconstruction of Halob. salinarum does not agree in a straight-forward way with the three-dimensional, electron crystallographic map of negatively stained Halof. volcanii envelopes, although the main features of the lattice and the morphological units are evident. The tomographic reconstruction of sections from epoxy-embedded material suffers from directional compression due to sectioning stress and continuous dimensional changes and mass loss due to electron irradiation. This communication consists, therefore, of three parts: (a) a comparison of the projection maps of negatively stained envelopes of Halof. volcanii and Halob. salinarum; (b) a comparison of the three-dimensional maps obtained by electron crystallography (Halof. volcanii) and low-dose cryotomography (Halob. salinarum); and (c) a methodological study of mass loss and dimensional changes of plastic-embedded material under low-dose conditions at room and liquid nitrogen temperatures. (C) 2000 Academic Press.
UR - http://www.scopus.com/inward/record.url?scp=0033927978&partnerID=8YFLogxK
U2 - 10.1006/jsbi.2000.4215
DO - 10.1006/jsbi.2000.4215
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C2 - 10806087
AN - SCOPUS:0033927978
SN - 1047-8477
VL - 130
SP - 10
EP - 26
JO - Journal of Structural Biology
JF - Journal of Structural Biology
IS - 1
ER -