A review of: Marhaeni B, Radjasa OK, Khoeri MM, Sabdono A, Bengen DG, Sudoyo H (2011) Antifouling activity of bacterial symbionts of sea grasses against marine biofilm-forming bacteria. Journal of Environmental Protection, 2: 1245-1249.
Biofouling is a natural process that arises as a result of organism growth on water submerged surfaces, which can result in economic losses to marine industries. Bacteria are considered the primary and dominant colonizers, facilitating the attachment and development of fouling communities. The use of anti-fouling paints like tributyl-tin can disrupt the growth of biofilms, but long term use is a serious environmental concern to marine ecosystems. The European Union, International Marine Organization and the Maritime Environment Protection Committee have restricted the use of hazardous anti-fouling agents, thus the search and development of alternative and environmentally friendly anti-foulants has gained momentum in recent years.
Sea grasses are productive coastal ecosystems and are a rich source of secondary metabolites with possible ecologically important roles in preventing surface fouling. It has been reported previously that sea grasses Cymodocea serrulata and Syringodium isoetifolium are able to inhibit the growth of marine biofilm-forming bacteria, most likely as a consequence of the association between specific marine bacteria and sea grasses, which could provide an alternative to commercial metal-based antifouling coatings. Using antibacterial assays, the study conducted by Marhaeni et al (2011) aimed to investigate the potential of marine bacteria associated with sea grasses Thalassia hemprichii and Enhalus acoroides for controlling the growth of marine biofilm-forming bacteria.
Four bacterial symbionts of the two sea grasses were found to inhibit biofilm-forming bacteria ranging from one to six different species, with three isolates from E. acoroides and one isolate from T. hemprichii. The active bacterial isolates were closely related to the members of the genus Bacillus and Virgibacillus, with 98-99% gene homology. Several studies have also revealed broad spectrum inhibition of growth by Bacillus and Virgibacillus symbionts isolated from sea sponge Pseudoceratina purpurea and soft coral Sinularia sp. Moreover, the Virgibacillus isolate from Sinularia sp. was found to be effective at inhibiting the growth of multi-drug resistant strains of Staphylococcus aureus.
The study elucidates the potential of bacterial symbionts from sea grasses E. acoroides and T. hemprichii as an alternative source of environmentally friendly marine antifouling agents. The secondary metabolite(s) responsible for the desired biological activity remain uncharacterised and the progression from the described investigation would be to isolate and purify the active antifouling compounds and to test them on a wide range of biofilm producing marine organisms to determine specificity.
5 comments:
That was a really interesting post Mario. It is amazing that the bacterial symbionts could have such a broad spectrum of inhibition against other bacteria. Do you think it is likely that a numerous active compounds are being produced to prevent the growth of bacteria because it affects such a broad spectrum of bacteria even including the problematic Staphylococcus aureus? If this is the case it would make the identification of the compounds much more difficult and so more expensive and time consuming.
Hey Dave,
Thanks for the comment. I have read a few papers on secondary metabolites produced by different marine bacteria which have inhibitory action against numerous species of bacteria. It is very possible that there is more than one active compound being produced by a given bacteria or community of bacteria with antagonistic effects to others, including drug resistant strains. To me it highlights the competitive nature of bacterial communities and so having defence mechanisms to out compete competitors is a necessary evolutionary adaptation. Bacteria are known to produce a range of bacteriocins which kill off unwanted colonizers and perhaps some of them are very broad range.
Regarding the sea grass bacteria, I imagine these compounds that inhibit biofilm-forming microbes is beneficial to both the bacteria and the sea grass host. I suspect the symbiont bacteria are suited to live on sea grass surfaces. The host benefits as well as I envisage that biofilms forming on the surface of sea grasses would eventually kill the sea grass, perhaps by affecting photosynthesis by blocking out light etc. I also suspect the sea grass-microbe association is also a relatively recent one based on the fact that ancestors of sea grasses were land based angiosperms.
Forgot to add, I suppose you are right that the characterization of several active compounds can be cumbersome and expensive. A friend of mine doing his Phd in marine biology in the Philippines is isolating active compounds from sea sponges using HPLC, which apparently can be a complex and long process. However, if there are significant benefits to be gained from isolating and mass producing a compound or compounds as described in the study, I'm sure industry will find a way to make it economically viable and profitable :)
That is fascinating; I had no idea that land based angiosperms were once the ancestors of seagrasses. The importance of this symbiotic relationship is incredible considering the comparatively recent association.
Also biofilms could have an effect on the pathway of nutrients. Biofilms could create a block between the roots of the sea grasses from the nutrients found in the sediments.
Also further understand of this symbiotic relationship would be important in the protection of the seagrasses. This would be of particular interest as there are many other organisms from all phyla that are closely associated with seagrasses making them an integral part of marine ecosystems.
You are right the money and the time will undoubtedly be invested considering the enormous economic loss that biofouling causes.
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