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The many modes of microbial magic

by Giuliana Viglione
August 3, 2019 | A version of this story appeared in Volume 97, Issue 31


A new kind of artists’ colony

A portrait of Audrey Hepburn is made out of E. coli bacteria in a petri dish.
Credit: Julie Paulssen/Petri Dish Picasso
It's alive: This petri dish painting is made of microorganisms.

You may have heard of living painting pageants, where people in costume recreate famous works of art. But have you heard about living paint?

Petri Dish Picasso is a Canada-based, student-run society dedicated to educating the public about microbiology and genetically modified organisms through the magic of petri dish art. The group, comprising mostly graduate students at local universities, brings its painting supplies and microbial expertise to local outreach events and groups, such as the Calgary Boys and Girls Club.

Petri Dish Picasso formed to address some common misconceptions about the dangers of microbes, according to Courtney Toth, who helps run the group. “There’s lots of examples of good microbes out there,” she tells Newscripts. “They’re just not the ones that we talk about all the time.”

The paints that the group uses are strains of Escherichia coli bacteria cloned with variants of a fluorescent jellyfish protein to give them their different hues. The artists scratch their designs on agar plates with plastic sticks dipped in E. coli. The bacterial colonies then need about 24 h to grow, doubling more than 50 times until they are visible to the naked eye. Because the artists can’t see the colors when the bacteria are applied, the painting process is tricky. “Every time, it’s a bit of a surprise,” says Julie Paulssen, a master’s student in environmental microbiology at the University of Calgary and one of the leaders of the group, which is now in its sixth year.

Since its founding, Petri Dish Picasso has spawned a second chapter at the University of Toronto, gained thousands of social media followers with its splashy Instagram and Twitter accounts, and expanded from a single event to three to five per chapter per year, Paulssen says.

Toth attributes the group’s success to the emotional response people have to the combination of art and science. The art, she says, makes the microbiology “a little more engaging and a little more immersive.”


Yeast common denominator

Three loaves of sourdough bread that were baked using a centuries-old sourdough starter
Credit: Carl's Friends
172 years in the baking: This sourdough was made with an Oregon Trail starter.

In 1847, as so many thousands did, Carl Griffith’s great-grandmother started out west from Missouri on the Oregon Trail. In tow was her sourdough starter—a soggy combination of flour, water, and wild yeast and bacteria.

For the sourdough uninitiated, a starter is the original leavening agent. Back in the days before commercial yeast was available, a fully developed starter would be used to give bread a head start before kneading, proofing, and baking. Starters are still used to make sourdough today, and while you can make your own starter, many are passed down for generations.

Among the most common microbes found in starters is Lactobacillus which produces lactic and acetic acids during the fermentation process. These bacterial by-products are what give sourdough its characteristic tang. And depending on where a starter was grown, it has a different combination of bacteria and yeasts—and a different flavor.

For years, Griffith was active in an early-internet forum for sourdough enthusiasts. For only the cost of postage, he would mail a few teaspoons of desiccated starter, taken from a sustained stash of his great-grandmother’s starter, anywhere in the world. Accompanying the starter would be instructions for reviving the culture and a family recipe booklet. After Griffith’s death in 2000, Dick Adams and several other forum members came together to keep the Griffith sourdough legacy going.

The 1847 Oregon Trail Sourdough Preservation Society, more commonly known as Carl’s Friends, has carried on Griffith’s tradition ever since. The well-leavened crew includes a chief starter grower, a backup starter grower, a keeper of the mailbox, and several culture keepers, who have to promise to keep only the Oregon Trail starter in their homes to prevent cross contamination. Adams reckons the group still gets anywhere from 30 to 90 requests per week, spreading Griffith’s starter across the country.

Newscripts readers can rise to the challenge and try their hand at baking with the original Oregon Trail starter by reaching out to Carl’s Friends.

Giuliana Viglione wrote this week’s column. Please send comments and suggestions to


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