The importance of collecting dirt

A report in the journal eLife described how researchers from Rockefeller University are evaluating soil samples from five continents and several oceanic islands to establish likely places to find new drugs. Rather than sequencing and analysing whole genomes of bacteria in the samples the researchers are looking for certain types of gene clusters which have been identified as good sources of therapeutics. Some of the samples were submitted by the public via a ‘Drugs from Dirt’ initiative but, such has been the success of the initiative, their website (http://www.drugsfromdirt.org) announced that they have had to restrict — temporarily one hopes — the collection of samples to the USA only.

Finding new drugs by studying soil samples is not new and this story reminded me that 50 years ago a soil sample collected on an isolated island was investigated, found potentially useful then discarded. Only a researcher’s persistence led to a drug that proved life-saving to some transplant patients, rapamycin.

In 1965 a Canadian expedition collected samples from Rano Kau, one of the three main volcanoes which formed the distinctive triangular shape of Easter Island. In 1972 researchers, led by Dr Suren Sehgal at Ayerst’s laboratories at Montreal, identified and isolated a compound secreted from a bacteria, Streptomyces hygroscopicus, in the sample. The compound proved to not only have potent anti-fungal properties but also suppressed the immune system whereupon it was sent to the National Cancer Institute for further testing.

Unfortunately, corporate priorities changed and the facilities at Montreal were closed, 95% of the staff were laid off and those remaining moved to a smaller unit. The company decided not to pursue the new drug but Sehgal could not bring himself to destroy the work as he had been instructed so he hid a few vials of Streptomyces hygroscopicus in his home freezer. When Ayerst merged with Wyeth Laboratories in 1987, Sehgal resumed his research.

Rapamycin, which was named after the islanders own name, Rapa Nui, for what we call Easter Island, is now made synthetically and with its derivatives has been used to prevent the rejection of organs after transplants, as a coating on cardiac stents and against certain kidney, lung and breast cancers.

Subsequently, claims have been made that the drug can not only extend life by delaying the onset of diseases such as cancer, heart disease and Alzheimer’s disease but also postpone the effects of normal aging. However, while rapamycin can increase the lifespan in mice the effect seems to be related to the drug’s suppression of tumours which represent the main cause of death in these mouse strains. The media frenzy about a new anti-aging pill was somewhat premature but the story illustrates the continuing importance of collecting soil samples.