153
It was demonstrated that the strains of Pseudomonas aeruginosa lacking CheR1
methyltransferase, fail to express chemotactic amino acids required for surface
adherence and maturation of biofilm.
Although polysaccharide intercellular adhesion, PIA, is the main molecule
responsible for biofilm formation, PIA independent biofilm formation occurs
wherein adhesive proteins substitute for PIA. Aggregation associated protein: AAP
is most widely studied among such staphylococcal adhesins. Other adhesin proteins
involved in biofilm formation are SSP-1 and SSP-2 proteins, which are identical to
AAP. Staphylococcus surface proteins (SSP) contributes to cell-cell adhesion by
forming protein strands on the Staphylococcus epidermidis surface. Another protein
from Staphylococcus aureus isolates named biofilm associated protein, Bap, is
involved in adherence to polystyrene surfaces, intercellular interactions, and biofilm
formation (Cucarella et al. 2001).
7.2.5 Biofilm Matrix Polysaccharides
One of the most striking features of biofilms that differentiates them from planktonic counterpart is the presence of extracellular matrix that encapsulates the biofilm bacteria and determines the architecture of mature biofilm. Extracellular matrix
production is essential feature for maturation of biofilm structure. The matrix is a
complex structure mostly composed of water (97%), rest it consists of exopolysaccharide polymer, lipids/phospholipids, nucleic acids, proteins, absorbed metabolites
and nutrients (Ghannoum and O’Toole 2001). Composition of extracellular matrix
produced by different bacteria is presented in Table 7.1.
Although Extracellular matrix is a characteristic feature of biofilms, its role is
not fully understood. Some of the designated roles for Extracellular matrix are (i)
acts as a hydrated viscous layer protecting embedded bacteria from desiccation; (ii)
provides protective layer that prevents bacteria from being recognized by the
immune system; (iii) acts as a diffusion barrier thus protects from routine antimicrobials; (iv) act as a sink for toxic molecules (antimicrobials, hydroxyl radicals, and
superoxide anions); and (v) contribute to development of phenotypic resistance of
Table 7.1 Composition of extracellular matrix of representative bacteria
Bacteria
Composition of extracellular matrix
E. coli
Extra polymeric substance (β-1,6-GlcNAc), lipids/phospholipids, nucleic acids,
proteins, absorbed metabolites and nutrients
P.
aeruginosa
Extra polymeric substance (alginate, Pel and/or Psl), lipids, membrane vesicles,
fimbriae, cupA, Typre IV pili
B. subtilis
Extra polymeric substance, extracellular proteins like TasA, fimbriae, eDNA,
lipids, pili
S. aureus
Extra polymeric substance (poly-b-1,6-N-acetylglucosamine), adhesive proteins
like Biofilm associated protein (bap) and accumulation associated protein (Aap),
lipids and Edna
7 Control of Bacterial Biofilms for Mitigating Antimicrobial Resistance
It was demonstrated that the strains of Pseudomonas aeruginosa lacking CheR1
methyltransferase, fail to express chemotactic amino acids required for surface
adherence and maturation of biofilm.
Although polysaccharide intercellular adhesion, PIA, is the main molecule
responsible for biofilm formation, PIA independent biofilm formation occurs
wherein adhesive proteins substitute for PIA. Aggregation associated protein: AAP
is most widely studied among such staphylococcal adhesins. Other adhesin proteins
involved in biofilm formation are SSP-1 and SSP-2 proteins, which are identical to
AAP. Staphylococcus surface proteins (SSP) contributes to cell-cell adhesion by
forming protein strands on the Staphylococcus epidermidis surface. Another protein
from Staphylococcus aureus isolates named biofilm associated protein, Bap, is
involved in adherence to polystyrene surfaces, intercellular interactions, and biofilm
formation (Cucarella et al. 2001).
7.2.5 Biofilm Matrix Polysaccharides
One of the most striking features of biofilms that differentiates them from planktonic counterpart is the presence of extracellular matrix that encapsulates the biofilm bacteria and determines the architecture of mature biofilm. Extracellular matrix
production is essential feature for maturation of biofilm structure. The matrix is a
complex structure mostly composed of water (97%), rest it consists of exopolysaccharide polymer, lipids/phospholipids, nucleic acids, proteins, absorbed metabolites
and nutrients (Ghannoum and O’Toole 2001). Composition of extracellular matrix
produced by different bacteria is presented in Table 7.1.
Although Extracellular matrix is a characteristic feature of biofilms, its role is
not fully understood. Some of the designated roles for Extracellular matrix are (i)
acts as a hydrated viscous layer protecting embedded bacteria from desiccation; (ii)
provides protective layer that prevents bacteria from being recognized by the
immune system; (iii) acts as a diffusion barrier thus protects from routine antimicrobials; (iv) act as a sink for toxic molecules (antimicrobials, hydroxyl radicals, and
superoxide anions); and (v) contribute to development of phenotypic resistance of
Table 7.1 Composition of extracellular matrix of representative bacteria
Bacteria
Composition of extracellular matrix
E. coli
Extra polymeric substance (β-1,6-GlcNAc), lipids/phospholipids, nucleic acids,
proteins, absorbed metabolites and nutrients
P.
aeruginosa
Extra polymeric substance (alginate, Pel and/or Psl), lipids, membrane vesicles,
fimbriae, cupA, Typre IV pili
B. subtilis
Extra polymeric substance, extracellular proteins like TasA, fimbriae, eDNA,
lipids, pili
S. aureus
Extra polymeric substance (poly-b-1,6-N-acetylglucosamine), adhesive proteins
like Biofilm associated protein (bap) and accumulation associated protein (Aap),
lipids and Edna
7 Control of Bacterial Biofilms for Mitigating Antimicrobial Resistance