Strategies to Prevent Bacterial Adhesion on Biomaterials - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 165

7.2.1 Architecture of Bacterial Cell

Prokaryotic cells have several distinct surface layers that are briefl y men-
tioned below.
Capsules : If the high molecular weight polysaccharides fi lm deposits
strongly on the cell wall, it is called a capsule, and otherwise, it is known
as an extracellular material slime. The main function of these layers is to
avoid phagocytosis [28].
Cell wall : Gram staining classifi es bacteria on the basis of different
cell wall structures. A class of bacteria that are stained by gram stain are
named as gram positive bacteria and the rest are known as gram nega-
tive bacteria. The gram strain reacts with the peptidoglycane layer of bac-
teria and produces a crystal violet color [29]. The peptidoglycane layer
is comparatively thick and peripheral to the cell wall in gram

− positive

bacteria. Whereas, this layer is very thin in gram negative bacteria and is

located inbetween the inner membrane and outer membrane [30, 31]. The
difference in cell wall of both gram positive and gram negative bacteria is
shown in Figure 7.5. Other important constituents of the cell wall include
the following:
Peptidoglycan : Peptidoglycane is a long strand of alternating polymer
of N

−

− acetylmuramic acid (NAM) and N − acetylglucosamine (NAG) [32].

Highly − thick and crosslinked peptidoglycan layer is present in gram −

positive cells, while it is very thin in gram negative cells. The peptidogly-

can layer is the main target of antimicrobial activity [33].

−

LPS

Lipoprote
Peptidoglycan

Outer membrane

Periplasmic space

Phospholipid

Inner membrane

Protein

Cytoplasm

( a )

LTA

Peptidoglycan

Phospholipid

Cytoplasmic
membrane

Protein

Cytoplasm

( b )

Figure 7.5 Cell wall structure of (a) gram − negative, and (b) gram − positive

bacteria (adapted from ref. [23]).