Enzymes: the new control for marine biofouling?

A review of the paper: Khandeparker, L., Kumar, S.K, Significance of biofilm proteins in modulating cyprid metamorphosis of Balanus amphitrite (Cirripedia: Thoracica), 2011, Marine Ecology, 32, 509-520

Barnacles are well known to be an important component of the marine biofouling species. The settlement of the cyprids are known to be affected by both the biofilm of the substratum and the presence of other barnacles. Adult barnacles release settling cues in the form of protein complexes, which ecourage the cyprids to settle. Many microfouling species employ protein and glycoprotein polymers while attaching to surfaces and the presence of proteases would hydrolyse these and prevent settlement. This raises the question as to whether using proteases as a antifouling method would create a more natural solution to a long term problem. This study aimed to investigate whether the protease from marine bacteria would disrupt the proteins in biofilms, and therefore have subsequent effects on barnacle cyprid settlement.

The method from this paper was extremely long and complicated so I will try and describe it as best as I can! Adult broods were collected and kept in the lab. Nauplii released from these broods were separated and reared in beakers. Two day old cyprids were used in the tests. Microwell plates were exposed to three different treatments. The first was that they were left in seawater to allow a natural biofilm to form. They were also developed to have a monospecies microbial film of both Aeromonas salmonocida salmonocida and Bactillus brevis as these are both bacteria that produce proteases. Ten to fifteen cyprids were placed in a well along with either a concentration of proteases, some adult extract or fresh seawater as a control. Adult extract was made by crushing up adults with seawater and centrifuging. The microplates were then left for 4 days, with an observation every 24 hours. The observation looked for the amount of cyprid metamorphosis as this would stimulate the act of cyprid settlement in the natural environment.

The results found an increased amount of metamorphosis with the presence of adult extract and a decrease when treated with proteases. However, an increase in the concentration of the protease had no affect. They found that the influence of a natural biofilm was similar to that of the adult extract, and when these were combined there was a massive increase in metamorphosis. The presence of adult extract overcame the presence of A. salmonocida salmonocida but not of B. brevis showing that it can sometimes but not always supercede inhibitory cues. This study showed the importance of a good combination of the presence of adults and a healthy natural biofilm, in order for a large amount of cyprid settlement. Although this itself is not a new discovery, it also shows that proteases do indeed affect the settlement of bacteria. This could enable us to develop a more environmentally friendly source of antifouling, therefore decreasing the current damaging forms such as tributlyn.