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pathogenic bacterial biofilms leading to persistent infections. Besides, Extracellular
matrix also has a structural role in biofilm formation. Extracellular matrix’s stickiness allows bacteria to interact with each other and also, with the surface.
Polysaccharides (Cellulose) and the other components (eg. Curli) present in the
biofilm matrix may interact and thus, may participate in three dimensional mushroom like growth of the biofilm (White et al. 2003).
Polysaccharide intercellular adhesin (PIA), which is also known as PNAG (Polyb- 1,6-N-acetylglucosamine (β-1,6-GlcNAc)) is a polysaccharide polymer that is an
important matrix component of Staphylococcus aureus and Staphylococcus epidermidis biofilms and contributes to their virulence. In E. coli, an exopolysaccharide
named β-1,6-GlcNAc, or PGA, is important for both cell-cell interaction and attachment to surfaces. Metaperiodate or a b-hexosaminidase isolated from Actinobacillus
actinomycetemcomitans (DspB), depolymerizes PGA by degrading β-1, 6-GlcNAc.
This results in almost complete disruption and dispersion of the biofilm. In E. coli,
the synthesis (the PgaC glycosyltransferase), export and localization of the PGA
polymer is encoded by pgaABCD (or ycdSRQP) operon. The pgaABCD operon is
present in a variety of eubacteria. It has been proposed that β-1,6-GlcNAc adhesin
stabilizes biofilms of E. coli and other bacteria such as Actinobacillus pleuropneumoniae and A. actinomycetemcomitans (Kaplan et al. 2004).
P. aeruginosa produces 3 types of polysaccharides, namely alginate, pel and psl.
It was earlier shown that pel and psl polysacchardies are mainly produced by environmental strains. Although alginate is widely conserved among P. aeruginosa
strains, it is not important for biofilm formation in non-mucoid variants. However,
alginate severely affects the biofilm structure and resistance phenotype (Franklin
et al. 2011; da Silva et al. 2019).
Cellulose, a glucose polymer, is produced only by a few bacterial species such as
the model organism Gluconacetobacter xylinum. Using calcofluor dye it was shown
that cellulose production is common in Enterobacteriaceae, including Enterica
serovar enteritidis, Salmonella enterica serovar typhimurium, S. enterica subsp. and
commensal and pathogenic strains of E. coli, Citrobacter spp. and Enterobacter
spp. Cellulose production is clearly related to the rigid biofilm formation at the
liquid- air interface; these characteristics however, are highly strains/ serovar dependent besides on environmental conditions. Cellulose producing genes are constitutively expressed and organized as two divergently transcribed operons, bcsABZC
and bcsEFG. These genes are present in most entero bacterial genomes, including
Salmonella, E. coli, Shigella, Enterobacter, and Citrobacter. Moreover, cellulose
synthesis is allosterically controlled by a well known secondary messenger called
cyclic-di-GMP (c-di-GMP). Synthesis of two biofilm components, curli fimbriae
and cellulose in Salmonella typhimurium showed a characteristic phenotype on
Congo red agar plates, the red dry and rough (rdar) morphotype. Such morphotype
is also reported in E. coli, wherein cellulase treatment leads to biofilm dispersion
(Zogaj et al. 2003; Da Re and Ghigo 2006).
Colanic acid, a negatively charged complex polymer consists of glucose, galactose, fucose, and glucuronic acid. Under specific growth and environmental settings, colanic acid forms a protective capsule around the bacterial cell (for instance,
B. P. Singh et al.
pathogenic bacterial biofilms leading to persistent infections. Besides, Extracellular
matrix also has a structural role in biofilm formation. Extracellular matrix’s stickiness allows bacteria to interact with each other and also, with the surface.
Polysaccharides (Cellulose) and the other components (eg. Curli) present in the
biofilm matrix may interact and thus, may participate in three dimensional mushroom like growth of the biofilm (White et al. 2003).
Polysaccharide intercellular adhesin (PIA), which is also known as PNAG (Polyb- 1,6-N-acetylglucosamine (β-1,6-GlcNAc)) is a polysaccharide polymer that is an
important matrix component of Staphylococcus aureus and Staphylococcus epidermidis biofilms and contributes to their virulence. In E. coli, an exopolysaccharide
named β-1,6-GlcNAc, or PGA, is important for both cell-cell interaction and attachment to surfaces. Metaperiodate or a b-hexosaminidase isolated from Actinobacillus
actinomycetemcomitans (DspB), depolymerizes PGA by degrading β-1, 6-GlcNAc.
This results in almost complete disruption and dispersion of the biofilm. In E. coli,
the synthesis (the PgaC glycosyltransferase), export and localization of the PGA
polymer is encoded by pgaABCD (or ycdSRQP) operon. The pgaABCD operon is
present in a variety of eubacteria. It has been proposed that β-1,6-GlcNAc adhesin
stabilizes biofilms of E. coli and other bacteria such as Actinobacillus pleuropneumoniae and A. actinomycetemcomitans (Kaplan et al. 2004).
P. aeruginosa produces 3 types of polysaccharides, namely alginate, pel and psl.
It was earlier shown that pel and psl polysacchardies are mainly produced by environmental strains. Although alginate is widely conserved among P. aeruginosa
strains, it is not important for biofilm formation in non-mucoid variants. However,
alginate severely affects the biofilm structure and resistance phenotype (Franklin
et al. 2011; da Silva et al. 2019).
Cellulose, a glucose polymer, is produced only by a few bacterial species such as
the model organism Gluconacetobacter xylinum. Using calcofluor dye it was shown
that cellulose production is common in Enterobacteriaceae, including Enterica
serovar enteritidis, Salmonella enterica serovar typhimurium, S. enterica subsp. and
commensal and pathogenic strains of E. coli, Citrobacter spp. and Enterobacter
spp. Cellulose production is clearly related to the rigid biofilm formation at the
liquid- air interface; these characteristics however, are highly strains/ serovar dependent besides on environmental conditions. Cellulose producing genes are constitutively expressed and organized as two divergently transcribed operons, bcsABZC
and bcsEFG. These genes are present in most entero bacterial genomes, including
Salmonella, E. coli, Shigella, Enterobacter, and Citrobacter. Moreover, cellulose
synthesis is allosterically controlled by a well known secondary messenger called
cyclic-di-GMP (c-di-GMP). Synthesis of two biofilm components, curli fimbriae
and cellulose in Salmonella typhimurium showed a characteristic phenotype on
Congo red agar plates, the red dry and rough (rdar) morphotype. Such morphotype
is also reported in E. coli, wherein cellulase treatment leads to biofilm dispersion
(Zogaj et al. 2003; Da Re and Ghigo 2006).
Colanic acid, a negatively charged complex polymer consists of glucose, galactose, fucose, and glucuronic acid. Under specific growth and environmental settings, colanic acid forms a protective capsule around the bacterial cell (for instance,
B. P. Singh et al.