Home-brewed heroin could become a terrifying reality within two years following the creation of genetically modified yeast that can be used to make opiate drugs, experts have warned.
Scientists called for urgent action to prevent criminal organisations gaining access to the technology, which could allow them to abandon opium poppy farms and ply their illegal trade from a plethora of local "factories".
Their fears are spelled out in the leading journal Nature while a scientific paper describing key stages in the process of producing opiates from sugar-fed yeast appears in a sister publication.
Together with previously reported research, all the steps necessary to make morphine from yeast and glucose are now in place.
Converting morphine to raw and then purified heroin involves simple chemistry requiring no specialised skills.
Professor Tania Bubela, from the School of Public Health at the University of Alberta, Canada, said: "In principle, anyone with access to the yeast strain and basic skills in fermentation could grow morphine-producing yeast using a home-brew kit for beer-making."
Currently, illegal heroin is made from morphine extracted from opium poppies grown in countries such as Afghanistan, Burma, Laos and Mexico.
The aim of research was not to find an easy way to manufacture the drug but to open up new avenues for the production of therapeutic medicines.
The US and Canadian team is openly concerned about the potential dangers of the technology.
Lead author US bioengineer Dr John Dueber, from the University of California at Berkeley, said: "We're likely looking at a timeline of a couple of years, not a decade or more, when sugar-fed yeast could reliably produce a controlled substance.
"The time is now to think about policies to address this area of research.
"The field is moving surprisingly fast and we need to be out in front so that we can mitigate the potential for abuse."
In a Nature comment article, Prof Bubela and two US experts, Dr Kenneth Oye and Dr Chappell Lawson, from the Massachusetts Institute of Technology, describe the threat even more starkly and set out recommendations for global regulators and the scientific community.
They wrote: "Yeast-based production of opiates could provide an alternative system for current criminal networks, particularly in North America and Europe, where the drugs are in high demand.
"Because yeast is so easy to conceal, grow and transport, criminal syndicates and law-enforcement agencies would have difficulty controlling the distribution of an opiate-producing yeast strain.
"All told, decentralised and localised production would almost certainly reduce the cost and increase the availability of illegal opiates - substantially worsening a worldwide problem.
"Globally, more than 16 million people use opiates illegally."
The experts call for yeast strains to be controlled so they are difficult to cultivate and harvest, or only capable of producing opiates with limited street value.
Another safety measure could involve genetically engineering the yeast to make it dependent on unusual nutrients or to contain a DNA "watermark" that can be easily identified by law enforcement agencies.
New screening procedures were needed to help prevent criminals obtaining the DNA sequences needed to grow opiate-producing yeast strains from commercial organisations, said the experts.
They added that drug laws should be extended to cover the yeast strains, making their unauthorised release and distribution illegal.
The research, published in the journal Nature Chemical Biology, shows how key steps in the poppy's natural drug pathway can be replicated in yeast.
Dr Deuber's team genetically engineered brewer's yeast, Saccharomyces cerevisiae, to synthesise the poppy compound reticuline from a derivative of glucose.
Previous research had already described how the opiate drugs codeine and morphine can be produced from reticuline in yeast. What was missing until now was a way for yeast to manufacture its own reticuline.
Canadian microbiologist and co-author Professor Vincent Martin, from Concordia University in Quebec, said reticuline was a "molecular hub" in the benzylisoquinoline alkaloid (BIA) chemical pathway, a lynchpin for the manufacture of many therapeutic drugs.
"From there, we can explore many different paths to other potential drugs, not just opiates," he added.
Dr Deuber said: "What you really want to do from a fermentation perspective is to be able to feed the yeast glucose, which is a cheap sugar source, and have the yeast do all the chemical steps required downstream to make your target therapeutic drug.
"With our study, all the steps have been described and it's now a matter of linking them together and scaling up the process. It's not a trivial challenge, but it's doable."
