Your Kitchen Sponge Is a Better Home for Bacteria Than a Petri Dish

Its porous structure provides the ideal physical environment for different kinds of bacteria to thrive, according to new research

Image of a hand wringing out a soapy green and yellow kitchen sponge into a sink
Air pockets in a sponge mimic healthy soil, which has various nooks and crannies to host microbial communities.  Michael Bihlmayer / EyeEm via Getty Images

Scientists have discovered a common household item is the perfect host for bacteria: the kitchen sponge. According to the new research, a sponge is a better incubator for diverse bacterial communities than a laboratory petri dish. 

Some bacteria prefer living with a collection of microbial species, while others opt for solitude. Scientists at Duke University were curious how bacterial communities might change depending on the structural environment they called home. Healthy soil, for example, has various nooks and crannies for different bacteria to inhabit, Ken Kingery reports for Futurity.

“Bacteria are just like people living through the pandemic—some find it difficult being isolated while others thrive,” says study co-author Lingchong You, a professor of biomedical engineering at Duke, in a statement

In their study, published in the journal Nature Chemical Biology, researchers distributed different strains of E. coli onto plates with different numbers of wells, which functioned as isolated compartments. The large wells allowed microbial species to mix freely, while the small wells let species keep to themselves. After 30 hours, the team looked at the number and types of bacterial on each plate, which had anywhere from six to 1,536 wells, reports Anna Gibbs for Science News. The scientists found that a moderate level of physical separation, similar to the porous structure of a kitchen sponge, allowed both kinds of bacteria—those that live in groups and those that live alone—to thrive.

“In retrospect, it’s very, very intuitive,” says You. “Maybe that’s why it’s a really dirty thing—the structure of a sponge just makes a perfect home for microbes.”

The results suggest that, like soil, kitchen sponges could offer an ideal collection of small and large air pockets for different bacterial communities, per Robert Lea for Newsweek. After the researchers ran their initial experiments, they recreated the experiment on a sponge. They found that the bacterial community growing on a kitchen sponge was more diverse than those produced in laboratory petri dishes, which are designed to host bacteria.

In addition to its holey structure, a sponge also provides a damp environment that is full of food particles.

“Sponges are not really well-suited for kitchen hygiene,” says Markus Egert, a microbiologist at Furtwangen University in Villingen-Schwenningen, Germany, who was not involved in the study, to Science News. “There’s hardly any sterile surface at home, but the kitchen sponge is probably the most densely populated item at home.”

To keep bacterial growth to a minimum, experts recommend microwaving your kitchen sponge for one to two minutes, keeping it away from raw meat, and replacing it every couple of weeks.

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