Biofouling Control by Quorum Quenching 15.3 Quorum Quenching (QQ) 433
Part B | 15.3
be produced by Pseudomonas aeruginosa, P. syringae
strain B728a, Shewanella sp. strain MIB615, Streptomyces sp. strain M64, Anabaena sp. PCC7120, and
Ralstonia solanacearum GM1000. Oxidoreductases
from Bacillus megaterium CYP102A1, Burkholderia
sp. strain GG4, and Rhodococcus erythropolis W2 act
by substituting an oxo group with a hydroxyl group of
AHL [15.5, 6, 10, 13–17].
15.3.2 Quorum Sensing Inhibitors (QSIs)
A potential approach for inhibiting the process of BF
is to interfere with bacterial QS signals [15.5]. AHL
degraders have been isolated from guts of shrimp,
Penaeus vennamei, European seabass, Dicentrarchus
labrax L., and Asian seabass, Lates calcarifer. Antibiotic malyngolide produced by the cyanobacterium, Lyngbya majuscula inhibited QS at concentrations between
3:5757 M. Malyngamide C and 8-epi-malyngamide
C inhibited luminescence of LuxR-based E. coli reporter strains. Malyngamides A and B, which are structurally different from malyngamide C, were effective in
inhibiting QS-dependent violacein production by C. violaceum CV017.
Bacterial QSIs
The peptide antibiotic – siamycin I, produced by
Streptomyces sp. strain Y33-1, inhibits the gelatinase and gelatin biosynthesis activating pheromone,
which results in disruption of the biofilm formed
by Enterococcus faecalis. The unique feature of
siamycin is the ability to selectively inhibit the
growth of Gram-positive bacteria but show no effect on the growth of Gram-negative bacteria. Butyrolactones (2(3H)-furanones) from Streptomyces sp. act
as analogs of AHL. Naturally occurring intermediates of the butanolide (2(5H)-furanones) biosynthetic
pathway in Hortonia sp. and Streptomyces antibioticus have also been found to be effective. In Pseudomonas sp., cyclopeptides and their diketopiperazines act on the QS system. There are few but
certain secondary metabolites produced by bacteria:
(i) N-(2’-phenylethyl)-isobutyramide and 3-methyl-N(2’-phenylethyl)-butyramide produced by Halobacillus
alinus C42, and (ii) 2-N-pentyl-4-quinolinol by Alteromonas sp. affect antibiotic (Andrimid) production,
bioluminescence (HAI-1 pathway), and prevent surface colonization in different Vibrio spp. Based on
the molecular size and structure of the inhibitors,
phenylethylamides are AHL structural mimics that
compete for receptor binding sites.
QSIs from Plants
The traditional of use of plant products for the treatment
of BF and ailments has been attributed to the phytochemicals present in them. Plant extracts have been
found to act as QSI because of the similarity in their
chemical structure to that of QS signals (AHL) and
also because of their ability to degrade signal receptors (transcriptional activators, LuxR/LasR). -aminobutyric acid produced by plants acts as promoter for the
degradation of the AHL signal OHC 8 HSL by AttM, lactonase of A. tumefaciens, attenuating the QS-dependent
infection process. Pyrogallol, extracted from medicinal plants such as Emblica officinalis and its analogs
exhibit antagonism against AI-2. L-canavanine from
seed exudate of Medicago sativa affected QS-mediated
exopolysaccharide production. Curcuma longa, a wellknown spice plant produces curcumin, which inhibits
the expression of virulence genes of P. aeruginosa
PA01. QS-regulated activities such as biofilm formation in P. aeruginosa and AI-2-mediated QS in different Vibrio spp. have been reported to be affected
by cinnamaldehyde and its derivatives. Extracts from
leaves, flowers, fruit, and bark of Combretum albiflorum, Laurus nobilis, and Sonchus oleraceus were
also found to possess anti-QS activities. Flavan-3-ol
catechin, a flavonoid from the bark of C. albiflorum
reduces the production of QS-mediated virulence factors – pyocyanin, elastase, and biofilm formation by P.
aeruginosa PA01. QSIs have also been reported from
garlic. Phenolic plant secondary metabolites such as
salicylic acid stimulate AHL-lactonase enzyme expression. Aqueous extracts of edible plants and fruits such
as Ananas comosus, Musa paradiciaca, Manilkara zapota, and Ocimum sanctum have been tested as QSI
against violacein production by C. violaceum and pyocyanin pigment, staphylolytic protease, elastase production, and biofilm formation abilities of P. aeruginosa PA01. The QS system in Staphylococcus spp. consists of the AI RNA III activating protein (RAP) and
its target molecule (TRAP). Inhibition of RAP by RNA
III-inhibiting peptides (RIP) results in attenuation of
virulence. Hamamelitanin extracted from the bark of
Hamamelis virginiana (witch hazel), like RIP, did not
affect the growth of Staphylococcus spp., but inhibited
the QS regulator RNA III, and prevented biofilm formation and cell attachment in vitro. Evidence has also been
provided by implantation of grafts soaked in Hamamelitanin into animals, where it decreased the bacterial load
in comparison to control.
Extracts of the plants Moringa oliefera and Acacia nilotica, which contain gallic and ellagic acids,
Part B | 15.3
be produced by Pseudomonas aeruginosa, P. syringae
strain B728a, Shewanella sp. strain MIB615, Streptomyces sp. strain M64, Anabaena sp. PCC7120, and
Ralstonia solanacearum GM1000. Oxidoreductases
from Bacillus megaterium CYP102A1, Burkholderia
sp. strain GG4, and Rhodococcus erythropolis W2 act
by substituting an oxo group with a hydroxyl group of
AHL [15.5, 6, 10, 13–17].
15.3.2 Quorum Sensing Inhibitors (QSIs)
A potential approach for inhibiting the process of BF
is to interfere with bacterial QS signals [15.5]. AHL
degraders have been isolated from guts of shrimp,
Penaeus vennamei, European seabass, Dicentrarchus
labrax L., and Asian seabass, Lates calcarifer. Antibiotic malyngolide produced by the cyanobacterium, Lyngbya majuscula inhibited QS at concentrations between
3:5757 M. Malyngamide C and 8-epi-malyngamide
C inhibited luminescence of LuxR-based E. coli reporter strains. Malyngamides A and B, which are structurally different from malyngamide C, were effective in
inhibiting QS-dependent violacein production by C. violaceum CV017.
Bacterial QSIs
The peptide antibiotic – siamycin I, produced by
Streptomyces sp. strain Y33-1, inhibits the gelatinase and gelatin biosynthesis activating pheromone,
which results in disruption of the biofilm formed
by Enterococcus faecalis. The unique feature of
siamycin is the ability to selectively inhibit the
growth of Gram-positive bacteria but show no effect on the growth of Gram-negative bacteria. Butyrolactones (2(3H)-furanones) from Streptomyces sp. act
as analogs of AHL. Naturally occurring intermediates of the butanolide (2(5H)-furanones) biosynthetic
pathway in Hortonia sp. and Streptomyces antibioticus have also been found to be effective. In Pseudomonas sp., cyclopeptides and their diketopiperazines act on the QS system. There are few but
certain secondary metabolites produced by bacteria:
(i) N-(2’-phenylethyl)-isobutyramide and 3-methyl-N(2’-phenylethyl)-butyramide produced by Halobacillus
alinus C42, and (ii) 2-N-pentyl-4-quinolinol by Alteromonas sp. affect antibiotic (Andrimid) production,
bioluminescence (HAI-1 pathway), and prevent surface colonization in different Vibrio spp. Based on
the molecular size and structure of the inhibitors,
phenylethylamides are AHL structural mimics that
compete for receptor binding sites.
QSIs from Plants
The traditional of use of plant products for the treatment
of BF and ailments has been attributed to the phytochemicals present in them. Plant extracts have been
found to act as QSI because of the similarity in their
chemical structure to that of QS signals (AHL) and
also because of their ability to degrade signal receptors (transcriptional activators, LuxR/LasR). -aminobutyric acid produced by plants acts as promoter for the
degradation of the AHL signal OHC 8 HSL by AttM, lactonase of A. tumefaciens, attenuating the QS-dependent
infection process. Pyrogallol, extracted from medicinal plants such as Emblica officinalis and its analogs
exhibit antagonism against AI-2. L-canavanine from
seed exudate of Medicago sativa affected QS-mediated
exopolysaccharide production. Curcuma longa, a wellknown spice plant produces curcumin, which inhibits
the expression of virulence genes of P. aeruginosa
PA01. QS-regulated activities such as biofilm formation in P. aeruginosa and AI-2-mediated QS in different Vibrio spp. have been reported to be affected
by cinnamaldehyde and its derivatives. Extracts from
leaves, flowers, fruit, and bark of Combretum albiflorum, Laurus nobilis, and Sonchus oleraceus were
also found to possess anti-QS activities. Flavan-3-ol
catechin, a flavonoid from the bark of C. albiflorum
reduces the production of QS-mediated virulence factors – pyocyanin, elastase, and biofilm formation by P.
aeruginosa PA01. QSIs have also been reported from
garlic. Phenolic plant secondary metabolites such as
salicylic acid stimulate AHL-lactonase enzyme expression. Aqueous extracts of edible plants and fruits such
as Ananas comosus, Musa paradiciaca, Manilkara zapota, and Ocimum sanctum have been tested as QSI
against violacein production by C. violaceum and pyocyanin pigment, staphylolytic protease, elastase production, and biofilm formation abilities of P. aeruginosa PA01. The QS system in Staphylococcus spp. consists of the AI RNA III activating protein (RAP) and
its target molecule (TRAP). Inhibition of RAP by RNA
III-inhibiting peptides (RIP) results in attenuation of
virulence. Hamamelitanin extracted from the bark of
Hamamelis virginiana (witch hazel), like RIP, did not
affect the growth of Staphylococcus spp., but inhibited
the QS regulator RNA III, and prevented biofilm formation and cell attachment in vitro. Evidence has also been
provided by implantation of grafts soaked in Hamamelitanin into animals, where it decreased the bacterial load
in comparison to control.
Extracts of the plants Moringa oliefera and Acacia nilotica, which contain gallic and ellagic acids,