RESOLVING THE HIGH-RESOLUTION ARCHITECTURE, ASSEMBLY AND FUNCTIONAL REPERTOIRE OF BACTERIAL SYSTEMS BY IN VITRO ATOMIC FORCE MICROSCOPY - Life at the Nanoscale: Atomic Force Microscopy of Live Cells - page 73

4.1.1 Spore Morphology

AFM images of various species of air-dried Clostridium novyi-

NT 8 spores are presented in Fig. 4.2 . As illustrated in Fig. 4.2,

Bacillus 4-7 and

B . thuringiensis

and native spores are enclosed within an exosporium sacculus

(indicated with the letter

B. anthracis

in Fig. 4.2a ) , which is either larger than the
dimensions of the spore body ( Fig. 4.2a ) or tightly attached to the spore
coat as in the case of

E

spores were
found to be encased in amorphous shells composed by irregular amorphous
material ( Fig. 4.2d ) , with many spores exhibiting ~200 nm thick “shell tails”
at their poles.

B. anthracis spores ( Fig. 4.2b ). C. novyi-NT

(a) (b)

(c) (d)

Figure 4.2. AFM images of air-dried bacterial spores. (a) B. thuringiensis , (b) B.
anthracis spores. Exosporium is indicated with E

in (a). “Shell tail” in (d) is indicated with S in (d).

, (c) B. atrophaes and (d) C. novyi-NT

4.1.2 Spore Coat Architecture and Assembly

More than 50 spore coat proteins have been identiied by genomic

and proteomic analysis. 1-3,9 Despite the recent advances in biochemical
and genetic studies, 9 spore coat self-assembly is still poorly understood. In
particular, it is not clear which spore coat proteins form the various spore
coat layers, what their roles are in the coat assembly and, inally, which
proteins are surface-exposed and which ones are embedded beneath the
surface. The elucidation of bacterial spore coat architecture and structure-

Bacillus