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 90

scanning on a smaller spore area, the initially scanned area did not display
any tip-induced alterations (such as a larger degree of coat degradation).
Finally, when we did not image spores for more than an hour between two
scans, the coat degradation pattern had developed similarly when compared
with spores that were scanned continuously.
Spore germination provides an attractive experimental model system for
investigating the genesis of the bacterial peptidoglycan structure. Dormant
spore populations can be chemically cued to germinate with high synchrony, 49
allowing the generation of homogenous populations of emergent vegetative
cells suitable for structural analysis.
Proposed models for the bacterial cell wall structure posit that
peptidoglycan strands are arranged either parallel (planar model) or
orthogonal (scaffold model) to the cell membrane. 55 Existing experimental
techniques are unable to conirm either the planar or the orthogonal model.
The experiments described here do not contain suficient high-resolution
data, in particular of individual peptidoglycan strands, to deduce with
certainty the tertiary three-dimensional peptidoglycan structure. The pore
structures ( Figs. 4.10 and 4.12 ) of the emergent germ and mature vegetative
cell wall — an array of pores — suggest a parallel orientation of glycan strands
with peptide stems positioned in stacked orthogonal planes. 55 More detailed
studies of germ cell surface architecture and morphogenesis will be required
to conirm this peptidoglycan architecture and to investigate whether glycan
biosynthesis precedes peptide cross-linking.
The results presented here demonstrate that AFM has the capacity

to provide important insight into the time-dependent structural dynamics of
individual germinating spores and cell wall high-resolution architecture. This
approach could be potentially utilized for the unravelling of the biological
role of the cell wall in critical cellular processes and antibiotic resistance.

in vitro

4.3 PROBING THE BACTERIALMINERAL INTERACTIONS ON
THE SURFACES OF METALRESISTANT BACTERIA

We are currently conducting studies on the elucidation of bioremediation
mechanisms of is

a Gram-positive and chromium (VI)-resistant bacterium, which can reduce
highly mobile, carcinogenic, mutagenic and toxic hexavalent chromium to less
mobile and much less toxic trivalent chromium. Toxic compounds and heavy
metals can be removed from contaminated sites or waste by chemical and
physical techniques, which are both dificult and expensive. The extraordinary
ability of indigenous microorganisms, like metal-resistant bacteria, for

Arthrobacter oxydans metal-resistant bacteria. A. oxydans