Chemical clues for understanding underwater attachment of large NZ seaweed

What is it about?

The paper describes studies on marine bio-adhesives. These are remarkable natural glues that can secure very large structures – kelp weighing up to 50 kg – to surfaces in wet environments in which the plant is subjected to very strong tidal forces. The fact that these glues are so durable and can work in a wet environment means that they have real potential in medicine. In this work we looked at zygotes of two species of seaweed. The zygote is the plant at its earliest stage and as such it has nothing to secure itself to except its bio-adhesive. These are species that have male and female plants and their gametes have to meet to form the zygote which is then the viable plant. In our experiments gametes were mixed to trigger zygote formation and the chemistry that occurs upon fertilisation. Two types of species were looked at – both grow in New Zealand waters (they were collected from Shag Point in the South Island), one is very vigorous in exposed waters with strong tidal flow (Durvillaea Antarctica) and the other grows in more sheltered areas (Hormosira banksii).

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Why is it important?

A time-lapse experiment was conducted looking at the samples using optical microscopy – that is imaging the zygote and noting its behaviour upon fertilisation. This showed the growth of the bio-film but it does not tell us what the film is made of; for that we used infrared spectroscopy. This gives a molecular fingerprint of the molecules that are involved and thus allows one to determine the molecular makeup of biopolymers that are being secreted. If we know this we can start to look at synthetic materials that might have these durable properties. Because of our time-lapse experiments we can see the bio-adhesive growing. We find that sulfonated polysaccharides are present in the adhesive of both species but the Durvillaea Antarctica produces this at a faster rate with the Hormosira banksia showing polyphenolics. This second group of molecules have been long considered important in all seaweed (and in mussel) adhesion yet our studies show this is not the case with the plant growing in more aggressive conditions (Durvillaea Antarctica) not showing any spectral fingerprint from polyphenols.