Part B | 15.4
436 Part B Tools and Methods in Marine Biotechnology
molecular architectures, e.g., siloxane-fluorinated linear, graft, block, or hyperbranched (co)polymers can
add to these AF agents. Coatings incorporating low
surface energy fluorinated moieties with hydrophilic
poly(ethylene glycol) (PEG) also have strong AF properties against marine organisms. The ability of amphiphilic coatings to lower the adhesion strength of
organisms is probably due to certain unique features:
(i) the low interfacial tension with water of the hydrophilic PEGylated domains, and (ii) the non-sticky
and slippery behavior of the hydrophobic perfluoroalkyl
domains [15.35].
Urethane polymers alone have little fouling resistance but provide mechanical strength, whereas siloxanes are not mechanically strong but have foulingrelease properties. The AF properties of polysiloxane polymers were also improved by the inclusion of
biocides (quaternary ammonium compounds (quats)).
Coatings with 18C length quats were effective in inhibiting bacterial biofilm formation. In contrast, 14C
quats were effective as growth inhibitors of diatom
Navicula sp. [15.8].
15.3.4 Fouling – Release Coatings
Commercially available fouling release coatings are
based on silicone elastomers, such as polydimethylsiloxane. Here, foulants adhere weakly to the substratum and are released under the hydrodynamic forces.
The use of biocides to control BF has not been effective against all microorganisms causing BF. Kojic acid incorporated into a non-toxic paint matrix at
a concentration of 0:5% significantly reduced the densities of bacteria and diatoms growing in paint. In
addition, it also decreased macrofouling over a period of 30 days. Kojic acid at non-toxic concentration
(330 M) inhibited bacterial density up to 2:53:2-fold
and diatom density up to 4:73:6-fold in biofilms on
glass slides. It was suggested that kojic acid reduced
the formation of microbial communities by inhibiting
non-QS regulatory cascades that affect biofilm formation. Alternative AF coatings employing copper and
co-biocides, e.g., Irgarol 1051, zinc pyrithione, and Sea
Nine 2011 are the principal replacement for tributyl tin
coatings [15.3, 4, 35].
15.4 Applications
Microbes isolated from the gut of marine organisms
such as shrimp, European seabass and Asian seabass
have helped to improve the survival of larvae of Macrobrachium rosenbergii, which can also tolerate a higher
concentration of ammonia. Microflora from the intestine of Ayu fish, Plecoglossus altivel, especially
Shewanella sp. strain MIB010, proved to be an AHL
degrader. It was effective in dispersing biofilms formed
by fish pathogens, Aeromonas and V. anguillarum. The
marine actinomycete, Streptomyces albus strain A66,
was also effective in disrupting the biofilm. Seabass
are inhabited by Gram-positive, Halobacillus salinus
C42, which release phenethyliamide compounds, especially 2,3-methyl-N-(2’-phenylethyl)-butyramide, to
inhibit bioluminescence of Vibrio harveyi. The marine
cyanobacterium Blennothrix cantharidosmum exudes
a variety of Tumonoic acids with the ability to inhibit bioluminescence, although not very strongly. D.
pulchra with the ability to produce furanones, inhibits
swarming motility in Proteus mirabilis and other phenotypes such as inhibition of luminescence and toxin
production. Ahnfeltiopsis flabelliformis, a macroalgae,
produces Floridoside, betonicine, and isethionic acid,
which act as QS signal quenchers. Bryozoa, Flustra
foliacea, isolated from the North sea, reduce a large variety of AHL signals through the action of bioactive
molecules such as bromo-tryptamine-based alkaloids.
A wide variety of sponges have been found to be
very effective as quorum quenchers – L. variabilis produces secomanoalide and manoalide to degrade AHL
signals. A nanofiltration membrane immobilized with
porcine kidney acylase I suppresses exopolysaccharide production and, consequently, inhibits biofilm formation. It has thus proven to be a very good AF
agent.
15.4.1 Clinical Settings
Biofilms are made up of proteins, polysaccharides,
and DNA These polymers can be targeted by enzymes, e.g., glycosylases [15.36]. Proteases can be
very efficient in breaking down the matrix, as has
been observed for Pseudoalteromonas. Dispersin B
(DspB) is a hexosaminidase, produced by a species of
Actinobacilli, and it attacks polysaccharide intercellular adhesin (PIA)–poly-N-acetyl glucosamine polysaccharide (PNAG) [15.37]. Its effectiveness was shown
through the prevention of biofilm formation by S.
epidermidis on implanted devices, precoating plastic
and polyurethane surfaces. DspB from the periodontal
436 Part B Tools and Methods in Marine Biotechnology
molecular architectures, e.g., siloxane-fluorinated linear, graft, block, or hyperbranched (co)polymers can
add to these AF agents. Coatings incorporating low
surface energy fluorinated moieties with hydrophilic
poly(ethylene glycol) (PEG) also have strong AF properties against marine organisms. The ability of amphiphilic coatings to lower the adhesion strength of
organisms is probably due to certain unique features:
(i) the low interfacial tension with water of the hydrophilic PEGylated domains, and (ii) the non-sticky
and slippery behavior of the hydrophobic perfluoroalkyl
domains [15.35].
Urethane polymers alone have little fouling resistance but provide mechanical strength, whereas siloxanes are not mechanically strong but have foulingrelease properties. The AF properties of polysiloxane polymers were also improved by the inclusion of
biocides (quaternary ammonium compounds (quats)).
Coatings with 18C length quats were effective in inhibiting bacterial biofilm formation. In contrast, 14C
quats were effective as growth inhibitors of diatom
Navicula sp. [15.8].
15.3.4 Fouling – Release Coatings
Commercially available fouling release coatings are
based on silicone elastomers, such as polydimethylsiloxane. Here, foulants adhere weakly to the substratum and are released under the hydrodynamic forces.
The use of biocides to control BF has not been effective against all microorganisms causing BF. Kojic acid incorporated into a non-toxic paint matrix at
a concentration of 0:5% significantly reduced the densities of bacteria and diatoms growing in paint. In
addition, it also decreased macrofouling over a period of 30 days. Kojic acid at non-toxic concentration
(330 M) inhibited bacterial density up to 2:53:2-fold
and diatom density up to 4:73:6-fold in biofilms on
glass slides. It was suggested that kojic acid reduced
the formation of microbial communities by inhibiting
non-QS regulatory cascades that affect biofilm formation. Alternative AF coatings employing copper and
co-biocides, e.g., Irgarol 1051, zinc pyrithione, and Sea
Nine 2011 are the principal replacement for tributyl tin
coatings [15.3, 4, 35].
15.4 Applications
Microbes isolated from the gut of marine organisms
such as shrimp, European seabass and Asian seabass
have helped to improve the survival of larvae of Macrobrachium rosenbergii, which can also tolerate a higher
concentration of ammonia. Microflora from the intestine of Ayu fish, Plecoglossus altivel, especially
Shewanella sp. strain MIB010, proved to be an AHL
degrader. It was effective in dispersing biofilms formed
by fish pathogens, Aeromonas and V. anguillarum. The
marine actinomycete, Streptomyces albus strain A66,
was also effective in disrupting the biofilm. Seabass
are inhabited by Gram-positive, Halobacillus salinus
C42, which release phenethyliamide compounds, especially 2,3-methyl-N-(2’-phenylethyl)-butyramide, to
inhibit bioluminescence of Vibrio harveyi. The marine
cyanobacterium Blennothrix cantharidosmum exudes
a variety of Tumonoic acids with the ability to inhibit bioluminescence, although not very strongly. D.
pulchra with the ability to produce furanones, inhibits
swarming motility in Proteus mirabilis and other phenotypes such as inhibition of luminescence and toxin
production. Ahnfeltiopsis flabelliformis, a macroalgae,
produces Floridoside, betonicine, and isethionic acid,
which act as QS signal quenchers. Bryozoa, Flustra
foliacea, isolated from the North sea, reduce a large variety of AHL signals through the action of bioactive
molecules such as bromo-tryptamine-based alkaloids.
A wide variety of sponges have been found to be
very effective as quorum quenchers – L. variabilis produces secomanoalide and manoalide to degrade AHL
signals. A nanofiltration membrane immobilized with
porcine kidney acylase I suppresses exopolysaccharide production and, consequently, inhibits biofilm formation. It has thus proven to be a very good AF
agent.
15.4.1 Clinical Settings
Biofilms are made up of proteins, polysaccharides,
and DNA These polymers can be targeted by enzymes, e.g., glycosylases [15.36]. Proteases can be
very efficient in breaking down the matrix, as has
been observed for Pseudoalteromonas. Dispersin B
(DspB) is a hexosaminidase, produced by a species of
Actinobacilli, and it attacks polysaccharide intercellular adhesin (PIA)–poly-N-acetyl glucosamine polysaccharide (PNAG) [15.37]. Its effectiveness was shown
through the prevention of biofilm formation by S.
epidermidis on implanted devices, precoating plastic
and polyurethane surfaces. DspB from the periodontal