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Biofilms on marine underwater surfaces can promote or inhibit
the settlement of other micro- and macrobiota,
such as macroalgal spores and invertebrate larvae.
The settlementmediating effects of biofilms probably
involve a variety of biofilm attributes, including
surface micro-topography and chemistry, as well
as a wide range of microbial products from small
metabolites to high-molecular weight extracellular
polymers. The settled organisms in turn can modify
microbial species composition of biofilms and
thus change the biofilm proper t ies and dynami
c s . A bet ter understanding of biofilm dynamics
and chemical signals released and/or stored by
biofilms will facilitate the development of antifouling
and of mariculture technologies alike.
A biofilm itself is distinguished from
other types of microbial aggregations by its
formation at interfaces. In euphotic marine
environments biofilms mainly consist of
phototrophic and heterotrophic bacteria, and
diatoms. Microbial cells in biofilms are
enmeshed in a matrix of extracellular polymers
(EPS) that are mainly composed of highmolecular
weight polysaccharides.
The structure of biofilms is complex and three-dimensional.
Gram-negative bacteria in biofilms produce cell-to-cell
communication signals (quorum sensing signals)
having effects on bacterial biofilm formation.
A broad range of marine invertebrate larvae utilize
biofilms as indicators of substratum suitability
for prospective settlement. Since the formation
of biofilms on newly submerged substrata as a
rule precedes colonisation by invertebrates, the
establishment of microbial biofilms is regardedas
a general prerequisite for the colonization of
macroorganisms such as invertebrate larvae and
algal spores.
Current antifouling technologies are based on
the application of toxic substances that can be
harmful to the natural environment. For this reason
and the global ban of tributyl tin (TBT), there
is a need for the development of ''environmentallyfriendly''
antifoulants. Marine microbes are promising potential
sources of non-toxic or lesstoxic antifouling
compounds as they can produce substances that
inhibit not only the attachment and/or growth
of microorganisms but also the settlement of invertebrate
larvae and macroalgal spores. Cyanobacteria are
much neglected in this respect, although they
produce a variety of bioactive metabolites that
may have allelochemical functions in the natural
environment, such as in the prevention of fouling
by colonizing organisms.
Chemical compounds from cyanobacteria
are also of biotechnological interest, especially for
clinical applications, because of their antibiotic,
algicidal, cytotoxic, immunosuppressive and
enzyme inhibiting activities.
Cyanobacterial metabolites have the
potential for use in antifouling technology, since
they show antibacterial, antialgal, antifungal and
antimacrofouling properties, which could be
exploited in the prevention of biofouling on madmade
substrates in the aquatic environment.
Molecules with antifouling activity represent a
number of types including fatty acids, lipopeptides,
amides, alkaloids, terpenoids, lactones, pyrroles
and steroids. The isolation of biogenic compounds
and the determination of their structure may provide
leads for future development of, for example,
environment friendly antifouling paints. An
advantage of exploring the efficacy of
cyanobacterial products is that the organisms can
be grown in mass culture, which can be
manipulated to achieve the optimal production of
bioactive substances. Phycotoxins and related
products from cyanobacteria may serve as
materials for antimicro- and antimacrofouling
applications.
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