The need for new biologically active compounds with applications as pharmaceuticals, nutraceuticals and cosmeceuticals is undeniable. In the very near future, there is a serious risk that a significant number of infections, particularly hospital-acquired infections, will be untreatable. There are no effective drugs for many forms of cancer. The obesity epidemic has created a need for “fat blockers.” New, safe and effective sunscreens are needed to protect the public from damaging UV radiation.
Are marine natural products the answer to these societal needs? Possibly. Natural products have fulfilled a critical role in the discovery of pharmaceuticals, not to mention their use in nutritional supplements and cosmetics. The marine environment has proven to be an exceptional resource for the discovery of bioactive natural products as is evident from the observation that more than 25,000 new metabolites have been isolated from marine biota in the past 30 years. Notably, the marine natural products Cytarabine, Yondelis and Eribulin (a derivative of a sponge metabolite) and monomethyl auristatin E (MMAE, a dolastatin derivative) have been approved for use in human chemotherapy. According to a 2014 review by David Newman and Gordon Cragg of the Natural Products Branch of the National Cancer Institute in Maryland, an additional 39 marine natural products or derivatives thereof are currently in clinical trials as anti-cancer and cancer pain control agents.
While the majority of promising marine natural products are isolated from invertebrates such as sponges and corals, it is now clear that most of these metabolites are produced by microbes associated with the host invertebrate. In general, it now appears that sponges and corals are not the talented chemists once assumed but rather, they provide an attractive environment for microbes to inhabit. The field of natural product discovery is built upon knowledge that there is a correlation between biodiversity and natural products diversity. Hence, the immense biodiversity of our oceans (there are approximately twice as many phyla in the oceans as there are on land) provides a critical, fertile ground for natural productsbioprospecting. The biodiversity is immense given that estimates of the microbial communities in each species of sponge and coral numbers in the thousands. While not all of these invertebrate-associated bacteria will be accomplished chemists, many have been found to exhibit such traits.
Our oceans, much like the rain forests, are suffering from a loss of biodiversity. Until recently, only two corals were listed in the Endangered Species Act, however, earlier this year, the US National Oceanic and Atmospheric Administration (NOAA) added an additional 20 species of coral to this list and a further 83 species are being considered for future listing. Clearly, the rate of loss of our marine biodiversity is occurring at an alarming rate. Given that each sponge or coral will contain thousands of microbial symbionts, loss of dozens of coral species could result in the loss of substantial biodiversity and, possibly, the loss of a life-saving cancer drug, a new class of antibiotic or a new sunscreen. The public is likely aware of the value of coral reefs in terms of the impact on tourism and fishing, however, the potential of microbes living within coral reef invertebrates to produce life-saving medicines and other bioproducts is likely not well understood. The World Ocean Assessment report is due at the end of 2014 and we would be well served to consider the impact of environmental damage on our access to yet-to-be discovered marine natural products.