Yeast under a microscope.

For less than a penny, a new fungal test could find deadly pathogens that contaminate water, spoil crops, and kill an estimated 2 million people in the developing world annually.

The new diagnostic, presented by Columbia University researchers recently in the journal Science Advances, was developed using one of the fungi that has helped humanity for millennia: baker’s yeast, or Saccharomyces cervisiae.

“We realized that the same household bakery’s yeast people use every day to brew beer and make bread could be programmed to detect a myriad of targets,” said Virginia Cornish, a Columbia chemist and the principal investigator on the project. “We can now alter the DNA of the baker’s yeast to give it new functions that make it useful for a variety of applications. The prospect of using this technology in rural communities with little access to high-tech diagnostics is particularly compelling.”

Their breakthrough came with some replacement and modification of the organisms, programming them to indicate their counterparts’ presence.

The scientists replaced the mating surface receptors of S. cerevisiae with analogues from Candida albicans, a gut bug that is one of the leading causes of death in immune-compromised people. They accomplished this by using a lithium acetate method of manipulation.

To highlight the detection signal, they used lycopene, an antioxidant found in plants, to change color.

The method proved reliable to try other major human pathogens, including Candida glabrata, Lodderomyces elongisporus, and P. brasiliensis, and other Paracoccidioides strains.

The team then developed a “one-step rapid dipstick prototype,” which was proven to detect the traces of the various germs in blood, urine, and soil, they report.

“This modular biosensor can be economically produced at large scale, is not reliant on cold-chain storage, can be detected without additional equipment, and is thus a compelling platform scalable to global surveillance of pathogens,” they conclude.

“It stands to impact agriculture and health, especially in developing countries, where it is arguably needed the most,” added Cornish.