Scientists probe yeast's ability to protect tree nuts

Jul 03, 2012 By Marcia Wood
Scientists probe yeast's ability to protect tree nuts
ARS scientists are determining how the yeast Pichia anomala can prevent a carcinogen-producing mold from infecting tree nuts such as pistachios, almonds, and walnuts. Photo by Scott Bauer.

(Phys.org) -- U.S. Department of Agriculture (USDA) scientists have moved a step closer to understanding the underlying mechanisms that enable a helpful yeast to disable a mold that attacks tree nuts such as almonds, pistachios, and walnuts. Their on-going laboratory studies may help improve the effectiveness of the yeast, Pichia anomala, in thwarting the mold, Aspergillus flavus.

The mold is of concern because it can produce , a natural carcinogen. Agricultural Research Service (ARS) Sui-Sheng T. (Sylvia) Hua leads the studies. She is based at the ARS Western Regional Research Center in Albany, Calif. ARS is USDA's chief intramural scientific research agency, and the research supports the USDA priority of ensuring food safety.

standards, and quality control procedures at U.S. packinghouses, help ensure that remain safe to eat. Nonetheless, growers and processors have a continuing interest in new, environmentally friendly ways to combat the A. flavus mold.

For an early, collaborative experiment by Hua and two other Albany scientists, Bradley J. Hernlem and Maria T. Brandl, the mold was exposed to the , and, later, to several different compounds that fluoresce a distinctive red, or green, when evidence of specific changes in the mold's cells is detected.

Results of these fluorescence assays, documented in a peer-reviewed article in the scientific journal Mycopathologia, suggest that the yeast interfered with the mold's energy-generating ATP (adenosine triphosphate) system, vital for the mold's survival. The findings also suggest that the yeast damaged mold cell walls and cell membranes, according to Hua. Walls and membranes perform the essential role of protecting cell contents.

In other work that has helped pave the way to current studies, the team used a different analytical procedure—quantitative reverse transcriptase PCR (polymerase chain reaction) assays—to analyze the activity of certain P. anomala genes in the presence of the mold. Preliminary findings, which Hua reported at the annual national meeting of the American Society for Microbiology in 2010, suggest that exposing the yeast to the mold may have triggered the yeast to turn on genes that code for production of two enzymes—PaEXG1 and PaEXG2. These enzymes are capable of degrading the mold's cell walls and causing damage to membranes.

Though further studies are needed, these early, PCR-based findings point to gene-controlled mechanisms that may be involved in the cell wall and cell membrane damage observed in the fluorescence assays.

Other ARS teams at Albany are also pursuing strategies for fighting A. flavus. Read more about this research in the July 2012 issue of Agricultural Research magazine.

Explore further: Tricking plants to see the light may control the most important twitch on Earth

add to favorites email to friend print save as pdf

Related Stories

Helpful yeast battles food-contaminating aflatoxin

Jan 27, 2010

Pistachios, almonds and other popular tree nuts might someday be routinely sprayed with a yeast called Pichia anomala. Laboratory and field studies by Agricultural Research Service (ARS) plant physiologist Sui-Sheng (Sylvi ...

Making tomorrow's bioenergy yeasts strong

Aug 25, 2011

Cornstalks, wheat straw, and other rough, fibrous, harvest-time leftovers may soon be less expensive to convert into cellulosic ethanol, thanks to U.S. Department of Agriculture (USDA) scientists' studies of a promising new ...

Live Christmas tree brings scent, mold

Nov 14, 2007

Live Christmas trees may bring more than a fresh evergreen scent to U.S. homes during the holidays, they may bring allergy symptoms, a study showed.

Recommended for you

Getting a jump on plant-fungal interactions

Jul 29, 2014

Fungal plant pathogens may need more flexible genomes in order to fully benefit from associating with their hosts. Transposable elements are commonly found with genes involved in symbioses.

The microbes make the sake brewery

Jul 24, 2014

A sake brewery has its own microbial terroir, meaning the microbial populations found on surfaces in the facility resemble those found in the product, creating the final flavor according to research published ahead of print ...

User comments : 0