Biology Reference
In-Depth Information
Chapter 15
SINGLEMOLECULE FORCE SPECTROSCOPY
OF MICROBIAL CELL ENVELOPE PROTEINS
Claire Verbelen, Vincent Dupres, David Alsteens, Guillaume Andre and
Yves F. DufrĂȘne
Institute of Condensed Matter and Nanosciences, Université catholique de Louvain,
Croix du Sud 2/18, B-1348 Louvain-la-Neuve, Belgium
Yves.Dufrene@uclouvain.be
15.1 PROBING THE MICROBIAL CELL ENVELOPE
Most microbes possess a well-deined cell envelope, consisting of a plasma
membrane and of a cell wall, that presumably evolved in the course of evolution
by selection in response to environmental and ecological pressures. 1 Because
the envelope represents the boundary between the external environment
and the cell, it plays several important roles, including determining cellular
shape, growth and division, enabling the organisms to resist turgor pressure,
acting as molecular sieves, interacting with drugs and mediating molecular
recognition and cellular interactions.
The functions of the cell envelope are directly related to its composition. The
wall mechanical strength in eubacteria is provided by peptidoglycan, consisting
of glycan chains cross-linked by short peptide chains. 1,2 Archaebacteria
possess stress-bearing wall components which may have different forms:
peptidoglycan-like polymers, proteinaceous sheats, crystalline glycoprotein
arrays (S-layers). In Gram-positive bacteria, anionic polymers (e.g., teichoic
acids) are bound to the cytoplasmic membrane (lipoteichoic acids) and
to the peptidoglycan layers (wall teichoic acids), while in Gram-negative
bacteria, the thin peptidoglycan layer is overlayed by an outer membrane,
i.e., an asymmetrical bilayer of phospholipids and lipopolysaccharides
 
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