Plant extracts have been used for thousands of years in the treatment of human diseases, yet natural products derived from microorganisms remained largely unexplored until the 20th century. Recent studies investigating microbial diversity in marine environments have found that marine microorganisms are a good source of biologically active compounds (bioactives). This paper provides a review of current understanding about bioactives from marine sources as well as recent advances which are enabling the discovery and development of novel drugs from marine microbial sources.
During 2007 there was a 38% increase in the number of new compounds derived from marine microbes. These compounds have a broad range of effects; including antimicrobial, antiprotozoan and antifouling. Marine microbes are more easily cultured compared to bioactive-producing eukaryotes and so are considered the best renewable source of these compounds.
Research has focused recently on epibiotic microbes which form biofilms on the surface of eukaryote hosts; these microbes are a rich source of novel bioactives. There are many examples of hosts benefitting from the bioactives produced by its associated microbes; bioactive molecules can prevent predation of the host or protect the host surface from over colonization. In return the microbes benefit from a nutrient rich environment. These microbes face fierce competition from other microbes living on the relatively nutrient-rich surface and by evolving allelochemicals such as antimicrobials, they can have a distinct advantage over other microbes.
The paper describes the procedure for the discovery of bioactive natural compounds including isolation, screening for antimicrobial activity and purification. It also discusses a number of obstacles such as unsuitable culture conditions, laborious purification processes and a lack of de-replication (i.e. minimising the rediscovery of already known compounds). The paper also describes recent technological advances which could help to overcome some of these challenges, as well as some of the possible alternatives to bioactive discovery. One example is high-throughput screening (HTS) of synthetic chemical libraries; libraries of chemically synthesised compounds are screened against defined targets to find an active compound. However a campaign to discover broad-spectrum antibiotics run by GlaxoSmithKline was abandoned after six years, owing to the limited chemical diversity of the screening libraries. So far it seems that natural product development is unrivalled.
I found this paper really interesting and easy to read. It was well structured and made use of a wide range of references, illustrating points with relevant examples. There is a real lack of viable alternatives to natural compounds, which justifies the need for further investigation of underexplored sources, and the paper makes lots of suggestions for further research.
A review of: Penesyan, A., Kjelleberg, S. and Egan, S. (2010) Development of novel drugs from marine surface associated microorganisms. Marine Drugs, 8: 438-459.
2 comments:
Great post Helen
This is a subject I find incredibly interesting as it links with my Plant exploitation module. We have learnt that it is very common for the natural products to be much better than any synthetic that can be constructed in a lab. This is because often there are numerous active compounds working in conjunction to produce the desired effect. The vast amount of time and money that would need to be invested to identify and isolate all active compounds makes it understandable that today natural products are still the most effective.
Cool post. It’s interesting to see that marine microbes are being considered as a sources for new compounds that could be developed in order to be exploited for medicinal purposes. Considering the historical, cultural and economical significance related to the utilisation and development of plant derived products, it could an exciting time if technological advancements would be able to ensure the reliable production of novel substances for various applications.
Nevertheless, if this does become a technologically and economically viable option in the future then it may be advisable to consider this additional productivity when assessing the resource wealth of the marine environment. Perhaps this could induce a shift in the perspective of how we view the world’s oceans with the potential of having a considerable effect upon the construction of management programmes defining the responsible maintenance of marine resources and the conservation of biota.
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