Sourdough Starters: Exploring Microscopic Life in Bread Making

New research demonstrates a simple way to predict how microbial species will live together, providing insights that could inform baking, food safety, and human⁢ health.

The⁢ researchers at Tufts University are using ⁢the bubbling mixtures of flour and water known as sourdough starters to explore what shapes life at the microscopic level.

Their findings appear ⁢in Ecology.

A major question in ecology is if ⁤it’s possible to predict which microbial species will thrive together based on how pairs of species interact, or if more complex group effects are needed to explain the patterns of coexistence of species seen in nature.

Some ‍ecologists are skeptical of using “pairwise interactions” to predict real microbial communities as of previous studies, which frequently enough featured artificial combinations of species or lab conditions⁤ unlike their⁤ natural⁢ habitats.

By studying ⁢microbes isolated from real sourdough cultures,the Tufts team showed that a simple pair-based model could reliably forecast⁤ how up to nine species of microbes will interact.

The same model may help explain how⁤ microbial communities behave in food facilities, farms, hospitals, and even‍ our own bodies. Realistic models could help scientists anticipate which species will persist and which will disappear-and foretell dangerous events such as foodborne‍ illness outbreaks or the emergence of antibiotic-resistant bacteria.

Sourdough starters work by cultivating wild yeasts and lactic acid bacteria that are already ⁣present in flour and⁢ in the surrounding environment, including on our hands and kitchen items. By mixing flour and water, bakers create the conditions that let these microbes awaken and begin to⁤ multiply until these microbial populations grow large and active enough to make dough rise and to give ⁣sourdough its distinctive tang.

“Sourdough starters include a wide diversity of microbes ” says ⁣the study’s senior author, Lawrence Uricchio, a professor of innovation and an assistant professor of biology at Tufts. “Yet within these starters, certain species consistently appear⁤ together in non-random patterns.” Most starters contain just a handful of bacterial species and one or two types of yeast.

Uricchio says this provided a perfect microcosm for testing if a simple model ⁤based on pairwise interactions could answer big-picture questions about how species will thrive in their natural environment. ⁣He compares pairwise interactions to predicting the outcome of a chess game when you know the strengths⁣ of each player.

But given that real ecosystems are much messier than a chess match, many scientists argue that natural ecosystems instead involve more complex interactions. Uricchio says these interactions are more like a game of rock, paper, scissors among three or more players. “With so many possible outcomes, i