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Architecture and High-Resolution Structure of Bacillus thuringiensis and Bacillus cereus Spore Coat Surfaces
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posted on 2005-08-16, 00:00 authored by Marco Plomp, Terrance J. Leighton, Katherine E. Wheeler, Alexander J. MalkinWe have utilized atomic force microscopy (AFM) to visualize the native surface topography and
ultrastructure of Bacillus thuringiensis and Bacillus cereus spores in water and in air. AFM was able to
resolve the nanostructure of the exosporium and three distinctive classes of appendages. Removal of the
exosporium exposed either a hexagonal honeycomb layer (B. thuringiensis) or a rodlet outer spore coat
layer (B. cereus). Removal of the rodlet structure from B. cereus spores revealed an underlying honeycomb
layer similar to that observed with B. thuringiensis spores. The periodicity of the rodlet structure on the
outer spore coat of B. cereus was ∼8 nm, and the length of the rodlets was limited to the cross-patched
domain structure of this layer to ∼200 nm. The lattice constant of the honeycomb structures was ∼9 nm
for both B. cereus and B. thuringiensis spores. Both honeycomb structures were composed of multiple,
disoriented domains with distinct boundaries. Our results demonstrate that variations in storage and
preparation procedures result in architectural changes in individual spore surfaces, which establish AFM
as a useful tool for evaluation of preparation and processing “fingerprints” of bacterial spores. These
results establish that high-resolution AFM has the capacity to reveal species-specific assembly and nanometer
scale structure of spore surfaces. These species-specific spore surface structural variations are correlated
with sequence divergences in a spore core structural protein SspE.