Sponge chemical biomimics as an anti-biofouling agent

A biofilm is a community of micro-organisms that adhere to each other on a surface. It is beneficial for the micro-organisms to form a community as it increases their growth rate, allows for a cooperative metabolism and the individuals are subject to fewer environmental changes. Biofilms may damage the surface that they have attached to, known as biofouling. Many researchers are therefore looking into ways in which biofilm formation can be reduced or ways that they can be broken down, this paper in particular looks into how anti-biofouling compounds derived from marine sponges may help to inhibit biofilms.

                Most antifouling techniques consist of coating submerged surfaces with a chemically enhanced paint which prevents the attachment of biofilms. Unfortunately the best coatings for this job are highly toxic and have been banned due to their adverse effects on the environment. Scientists have therefor been looking into other antifouling methods such as the use of biocides and there have been some promising results although many of the most promising antifouling agents are difficult to produce on a large-scale. Scientists are therefore looking into biomimetic compounds so that they are similar to a naturally occurring compound but also easy to produce.

Marine sponges are being looked into for anti-biofilm agents as they produce a wide variety of chemicals for their natural defence against predators and communication with symbiotic organisms. The majority of the anti-fouling chemicals that have been discovered in sponges have been bactericidal leaving just the terpenoids and pyrrole-imidazoles. Antifouling compounds that have been discovered in sponges include ageloxime-D 4, manoalides and pyrrole-Imidazole alkaloids. Although the mechanism by which ageloxime-D 4 reduces biofilm formation is not known the monoalides have been found to prevent bacterial attachment and biofilm formation by inhibiting quorum sensing in both gram-positive and gram-negative species. 

Pyrrole-Imidazole alkaloids (PIAs) are found exclusively in sponges and are known to prevent biofilm formation although, again, it is not yet known how. There has been research into the key structural elements of PIAs which provide them with their bioactivity, using this information it is possible for a similar molecule to be synthesized in large product yields. A synthetic compound known as TAGE (trans-bromoageliferin) has been developed which has been found to inhibit biofilm formation and disperse pre-existing biofilms without killing the microorganisms in the biofilm. Another synthetic PIA known as dihydrooroidin (DHO) has been found to have antifouling activity against Halomonas pacifica, a common fouling agent, when combined with a marine-based paint and used as a coating. Both of these compounds, unlike many natural PIAs, were found to be non-toxic and so could potentially be used in the field.

It is clear that synthetic PIAs have huge potential as anti-biofouling agents. Not only are they more easily produced on a large scale than the natural PIAs produced my sponges but they also don’t have the toxic effects, which were necessary for the sponges defences. Further research into these synthetic molecules is vital in finding the best anti-biofouling agent in the field.

Reference: Stowe, S. D. et al. (2011). Anti-Biofilm Compounds Derived from Marine Sponges. Marine drugs, 9, 2010-2035.