All Yeasts Are Not Created Equal

 Concordia biology professor Malcolm Whiteway identifies cellular variations that may lead to more effective treatments

Newswise, October 24, 2016— Yeast. Great if you want to make bread or wine. Not so hot if it turns up as Candida albicans in large quantities in your body and makes you sick.

A study recently published by a team of researchers led by Concordia University professor Malcolm Whiteway in Current Biology shows that the type of yeast in bread is less similar to the type that causes fungal infections than previously thought.

The researchers hope that by shining new light on what makes the pathogen tick, his research may eventually help create targeted drugs.

When yeast goes bad

Candida albicans is the strain of yeast that causes relatively benign infections in people with strong immune systems. But it can be a serious threat to people with compromised immune systems, such as patients with AIDS or those undergoing chemotherapy or transplants of organs or bone marrow.

“Blood-stream infections related to Candida are frequently fatal,” says Whiteway, who conducted the study with key collaborators Walters Tebung — a PhD candidate at Concordia, and Joachim Morschhauser with Germany’s Institut für Molekulare Infektionsbiologie.

Because the cells of this fungus function very similarly to human cells, the antibiotics that have been so successful in treating bacterial infections are not active against them.

And the current anti-fungal drugs can have serious side effects. My research is aimed at helping to develop a new generation of anti-fungal drugs that have limited side effects”

Yin yang yeast

Whiteway and his colleagues examined how a cellular process in Candida albicans differs from the one in Saccharomyces cerevisiae, the yeast used in making bread and wine. Through “genetic rewiring,” the protein controlling a particular process in one yeast species controls a different process in the other.

The rewiring occurs in a protein named Ppr1. In Candida albicans, this protein controls the degrading of purines — molecules that make up DNA.

But the Ppr1 protein in Saccharomyces cerevisiae controls the building of pyrimidines — molecules that make up the elements of DNA complementary to purines.

“Imagine two similar looking houses in Montreal and Toronto. In Montreal, when you flick a switch in the living room the lights come on. But when you flick the equivalent switch in the house in Toronto the stereo goes off. The same switch is doing different jobs,” says Whiteway, who also holds a Canada Research Chair in Microbial Genomics in the Faculty of Arts and Science.

“We think the reason for this is because the yeast that makes bread and wine changed its metabolism to allow it to grow without much oxygen. This led to the pressure that generated the rewiring,” he says.

New treatment options

Pinpointing differences between bread-making and disease-causing yeasts gives us a picture of how cells can be remarkably different even when they look similar. That’s important from a drug production standpoint. Right now, it's common practice to use Saccharomyces to develop drugs to fight Candida.

“This study proves that we have to study the pathogen itself. We can’t just study proxies and think drugs that will treat one will work in the other,” says Whiteway.

“If you want drugs to fight Candida you’re better off working with Candida, even though Saccharomyces is easier to come by. The more we understand about how a fungal cell works, the better we can identify weak points in its armour.”

“We hope it will one day lead to new treatment options for patients suffering from yeast infections, with the goal of faster healing and reduced suffering.”

Science Shows Cheese Can Make Wine Taste Better

Newswise, October 24, 2016--A new scientific study shows that eating cheese may actually increase how much someone likes the wine they are drinking.

The study, published in the October issue of the Journal of Food Science, used a new sensory evaluation method and found consuming cheese while drinking wine impacted the description and preference of different wines.

The study was conducted at the Center for Taste and Feeding Behavior in France with frequent wine and cheese consumers from the city of Dijon.

 The subjects evaluated four wines (Pacherenc, Sancerre, Bourgogne and Madiran) using a new sensory evaluation method developed by the researchers to show how perception and liking of wine change after cheese intake over several sips, which is closer to what happens in typical consumption.

The subjects were given a list of sensations which they used to indicate what caught their attention (called the dominant sensation) as they consumed the wine over three consecutive sips and after they swallowed.

Once the wines were initially evaluated, the task was repeated, but with a piece of cheese eaten in-between sips. Four different cheeses (Epoisses, Comté, Roquefort, Crottin de Chavignol) were sampled over different sessions with each wine.

Results showed that cheese consumption had an impact on the description for all wines, and impacted preference for most. None of the four cheeses included in the study had a negative impact on wine preference.

Liking of each wine was increased or remained the same after cheese intake. In both red wines (Bourgogne and Madiran), the four cheeses decreased the duration of dominance of astringency and increased that of red fruits aroma.

In the sweet white (Pacherenc), the duration of dominance of sweetness was not changed by cheese intake, but in the white dry wine, cheeses had an impact on the main aroma.

“Thanks to our research we learned that the duration of the perception of astringency of a certain wine could be reduced after having cheese and that the four evaluated cheeses had the same effect.

“In short, when having a plate of assorted cheeses, the wine will probably taste better no matter which one they choose,” lead author Mara V. Galmarini explained.

According to the authors, the sensory method developed in their work can help build better understanding of how the perception of one product is changed when consumed in combination with another. This information can help food brands communicate their products’ characteristics, thus improving consumers’ experiences.

Read the Journal of Food Science abstract here.

New Research sheds light on how Aged Wine gets its aroma

Newswise, October 17, 2016 — Researchers have discovered an enzyme that plays a leading role in the formation of compounds that give aged wines their sought-after aroma.

The enzyme is a member of the cytochrome P450 family of enzymes, which are involved in the formation and breakdown of various molecules and chemicals.

By analyzing a large sample of French grapes and white wines through a technique called liquid chromatograph mass spectrometry, the investigators found that, during grape growth, this enzyme (named CYP76F14) helps to convert a common plant compound, monoterpenol linalool, into a different compound, (E)-8-carboxylinalool.

The formation of this compound is an important next step on the road to aroma: as wine ages, (E)-8-carboxylinalool is gradually converted into wine lactone, which gives old wine its nose.

In addition to contributing to our understanding of where wine aroma comes from, this discovery could also impact the grapevine breeding and wine making industries, other fruit research and breeding, as well as aspects of aroma and scent in the beverage and food industries.

"Combining different analytical techniques was key in our work, and this broad picture helped us learn more about how common plant molecules are transformed into specific wine aroma," said Dr. Nicolas Navrot, senior author of the New Phytologist article.