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 84

Disassembly of the higher-order rodlet structure began prior to the
outgrowth stage of germination ( Fig. 4.9 ) . Disaggregation of the rodlet layer
occurred perpendicular to the orientation of individual rodlets, resulting in
the formation of banded remnants ( Fig. 4.9 ) . Further structural disruption
led to the formation of extended, 2-3 nm wide, ibrils (indicated with arrows
in Fig. 4.9e ) , which were also oriented perpendicular to the rodlet direction.

(a) (d)

(b)

(e)

(c)

Figure 4.9. (a-d) Series of AFM height images showing the progress of rodlet
disassembly. In the circled regions, banded remnants of rodlet structure (a) disassemble
into thinner ibrous structures (d). Time between images was 36 min. (a)-(b); 3 min.
(b)-(c); and 6 min. (c)-(d), for a total time between (a) and (d) of 45 min. In (b), the
area imaged in (c) is indicated with a light grey box. In (b) and (c), the area imaged
in (a) and (d) is indicated with a dark grey box. In (e), which is an enlarged part of
(d), arrows indicate the end point of rodlet disruption, i.e. ibrils with a diameter
of 2-3 nm, oriented roughly perpendicular to the rodlets. Images reproduced, with
permission from Ref. 7. © (2007) National Academy of Sciences, USA.

Several classes of proteins, with divergent primary sequences, were found
to form similar rodlet structures on the surfaces of cells of Gram-negative

E.

coli as well as spores of Gram-positive streptomycetes and

various fungi. 15 These rodlets were shown to be structurally highly similar
to amyloid ibrils. 15 Amyloids possess a characteristic cross-

and S. enterica

structure and
have been associated with neural degenerative diseases (i.e. Alzheimer's and
prion diseases). 52 Amyloid ibrils or rodlets form microbial surface layers and

B