Biofouling Control by Quorum Quenching 15.3 Quorum Quenching (QQ) 435
Part B | 15.3
Within sponge terpenoids, only ageloxime-D,
manoalide, and two manoalide congeners have been
reported to have the ability to interfere with bacterial
biofilm formation without disrupting cellular growth.
Besides terpenoids, marine sponges synthesize pyrroleimidazole alkaloids (PIA), another class of potent AF
molecules that is unique to their phylum only [15.31].
Many families of marine sponges are the source of
PIAs, but most of the work has been done on the bromopyrrole derivatives extracted from the Agelasidae
family [15.31].
Oroidin, sceptrin, and bromo ageliferin are natural PIA products that act as potent toxic AF compounds against microorganisms, as well as higher
organisms. Ageloxime-D, a diterpenoid metabolite,
()ageloxime-D 4, from a marine sponge, was shown
to inhibit biofilm formation by Staphylococcus epidermidis without inhibiting its growth, whereas its parent molecule, ()agelasine-D 5, showed the opposite
effect. Luffariella variabilis synthesizes as ester terpenoid–Manoalide – which exhibits both antibiotic and
anti-inflammatory activities. There are three additional
derivatives of Manoalide, viz. seco-manoalide, (E)neomanoalide, and (Z)-neomanoalide [15.31]. These
derivative compounds and their parent molecule were
tested for antibiotic activity and found to be effective
against Gram-positive bacteria only. In 2007, Skindersoe and co-workers found that extracts obtained from
L. variabilis act as potent QSI agents against both
Gram-negative and Gram-positive bacteria. This QSI
activity was attributed to the conserved 2(5H)-furanone
substituent [15.31].
Manoalides work as bactericides against Grampositive bacteria. Against Gram-negative bacteria, they
are not bactericidal but exhibit significant QSI activity. This shows that marine sponges are potential
sources for future biofilm modulator molecules, particularly against life-threatening infections caused by
Gram-negative pathogens like P. aeruginosa, A. baumannii, and Klebsiella pneumoniae [15.31].
15.3.3 Designing Antifouling Agents
Surface Adhesion
Efforts to modify the surface energy of substrates to
reduce adhesion (ca. 25 dynes cm
1 as the least hospitable) of organisms could not prevent the adhesion
of all fouling organisms. The question arises as to
which properties of the surface could be altered to
discourage/reduce cellular adhesion. Amphiphilic coating systems having both hydrophobic and hydrophilic
domains on the surface show excellent AF properties
for both diatoms and macroalgae. Cells adhere more
strongly to hydrophobic surfaces, presumably for better survival. Under stressed conditions, the cellular level
of nitric oxide (NO)is a good indicator. Levels of NO
were fourfold higher in cells on a hydrophilic surface than those on a hydrophobic surface (silicon),
indicating that hydrophobic surfaces were less stressful. Incorporation of such molecules that induce stress
in fouling organisms can make them potential candidates as AF agents. Trans,trans-2,4-decadienal (DD),
implicated as a chemical defense molecule, inhibits
the invertebrate grazing of phytoplankton. Since diatoms can produce DD, it can be exploited to disperse clumping of diatoms [15.4, 8]. Novel antibacterial
agents have been developed as NO-releasing silica
nanoparticles. With enhanced inhibitory activity and
reduced toxicity against P. aeruginosa and E. coli,
the strategy proved better than NO alone in removing
biofilms [15.32, 33].
Marine mammal skin is a clean surface, free of
all fouling organisms (epibionts). In the pilot whale
Globicephala melas, such a phenomenon is attributed
to nanobridge pores on the surface of the skin. The
nanobridge pores (0:11:2 m
2 ) are smaller than most
fouling organisms, and it is proposed that they provide
few micro niches or contact points for adhesion. These
skins thus reduce fouling by the common bacterium P.
aeruginosa to the extent of 93% in comparison with unprotected surfaces. In the dogfish egg case and sea stars
(echinoderms) are a unique group of organisms, whose
surface is free of any fouling organisms. Glycoproteins from some species blocked adhesion of bacteria
whilst adhesion was enhanced by glycoproteins from
other species. Production of free radicals has also been
proposed as an AF strategy for marine algae and barnacles. Shark skin is another case that demonstrates
that fouling can be controlled based on texture and
dimension [15.34].
Nanocomposites
Coatings made of amphiphilic diblock copolymers,
consisting of a poly(dimethyl-siloxane) block and
a PEGlyated (poly(ethylene glycolated)) fluoroalkyl
modified polystyrene block, have proved to possess excellent fouling release properties against the macroalga
Ulva linza. Enhancement in polymer performance can
be achieved through dispersal of nanosized fillers into
the polymeric matrix to create a nanocomposite. The
use of fluorosilicones, i. e., polymers containing both
siloxane and fluorinated moieties in diverse macro-
Part B | 15.3
Within sponge terpenoids, only ageloxime-D,
manoalide, and two manoalide congeners have been
reported to have the ability to interfere with bacterial
biofilm formation without disrupting cellular growth.
Besides terpenoids, marine sponges synthesize pyrroleimidazole alkaloids (PIA), another class of potent AF
molecules that is unique to their phylum only [15.31].
Many families of marine sponges are the source of
PIAs, but most of the work has been done on the bromopyrrole derivatives extracted from the Agelasidae
family [15.31].
Oroidin, sceptrin, and bromo ageliferin are natural PIA products that act as potent toxic AF compounds against microorganisms, as well as higher
organisms. Ageloxime-D, a diterpenoid metabolite,
()ageloxime-D 4, from a marine sponge, was shown
to inhibit biofilm formation by Staphylococcus epidermidis without inhibiting its growth, whereas its parent molecule, ()agelasine-D 5, showed the opposite
effect. Luffariella variabilis synthesizes as ester terpenoid–Manoalide – which exhibits both antibiotic and
anti-inflammatory activities. There are three additional
derivatives of Manoalide, viz. seco-manoalide, (E)neomanoalide, and (Z)-neomanoalide [15.31]. These
derivative compounds and their parent molecule were
tested for antibiotic activity and found to be effective
against Gram-positive bacteria only. In 2007, Skindersoe and co-workers found that extracts obtained from
L. variabilis act as potent QSI agents against both
Gram-negative and Gram-positive bacteria. This QSI
activity was attributed to the conserved 2(5H)-furanone
substituent [15.31].
Manoalides work as bactericides against Grampositive bacteria. Against Gram-negative bacteria, they
are not bactericidal but exhibit significant QSI activity. This shows that marine sponges are potential
sources for future biofilm modulator molecules, particularly against life-threatening infections caused by
Gram-negative pathogens like P. aeruginosa, A. baumannii, and Klebsiella pneumoniae [15.31].
15.3.3 Designing Antifouling Agents
Surface Adhesion
Efforts to modify the surface energy of substrates to
reduce adhesion (ca. 25 dynes cm
1 as the least hospitable) of organisms could not prevent the adhesion
of all fouling organisms. The question arises as to
which properties of the surface could be altered to
discourage/reduce cellular adhesion. Amphiphilic coating systems having both hydrophobic and hydrophilic
domains on the surface show excellent AF properties
for both diatoms and macroalgae. Cells adhere more
strongly to hydrophobic surfaces, presumably for better survival. Under stressed conditions, the cellular level
of nitric oxide (NO)is a good indicator. Levels of NO
were fourfold higher in cells on a hydrophilic surface than those on a hydrophobic surface (silicon),
indicating that hydrophobic surfaces were less stressful. Incorporation of such molecules that induce stress
in fouling organisms can make them potential candidates as AF agents. Trans,trans-2,4-decadienal (DD),
implicated as a chemical defense molecule, inhibits
the invertebrate grazing of phytoplankton. Since diatoms can produce DD, it can be exploited to disperse clumping of diatoms [15.4, 8]. Novel antibacterial
agents have been developed as NO-releasing silica
nanoparticles. With enhanced inhibitory activity and
reduced toxicity against P. aeruginosa and E. coli,
the strategy proved better than NO alone in removing
biofilms [15.32, 33].
Marine mammal skin is a clean surface, free of
all fouling organisms (epibionts). In the pilot whale
Globicephala melas, such a phenomenon is attributed
to nanobridge pores on the surface of the skin. The
nanobridge pores (0:11:2 m
2 ) are smaller than most
fouling organisms, and it is proposed that they provide
few micro niches or contact points for adhesion. These
skins thus reduce fouling by the common bacterium P.
aeruginosa to the extent of 93% in comparison with unprotected surfaces. In the dogfish egg case and sea stars
(echinoderms) are a unique group of organisms, whose
surface is free of any fouling organisms. Glycoproteins from some species blocked adhesion of bacteria
whilst adhesion was enhanced by glycoproteins from
other species. Production of free radicals has also been
proposed as an AF strategy for marine algae and barnacles. Shark skin is another case that demonstrates
that fouling can be controlled based on texture and
dimension [15.34].
Nanocomposites
Coatings made of amphiphilic diblock copolymers,
consisting of a poly(dimethyl-siloxane) block and
a PEGlyated (poly(ethylene glycolated)) fluoroalkyl
modified polystyrene block, have proved to possess excellent fouling release properties against the macroalga
Ulva linza. Enhancement in polymer performance can
be achieved through dispersal of nanosized fillers into
the polymeric matrix to create a nanocomposite. The
use of fluorosilicones, i. e., polymers containing both
siloxane and fluorinated moieties in diverse macro-