Ewww Alert: Your Kitchen Sponge Can Harbor More Kinds of Bacteria Than an Actual Petri Dish

Your kitchen sponge should be cleaner than the dirty dishes it comes in contact with, but if your sponge has been sitting in a puddle by your sink for several weeks, that may not be the case. It's no secret that old sponges are one of the germiest items we touch on a daily basis, and a new study revealed just how nasty they can get. As Smithsonian reports, sponges are capable of harboring more bacterial diversity than laboratory petri dishes.

Sponges sop up moisture and food particles—two components that make them attractive to microbes. According to a recent study published in the journal Nature Chemical Biology, the structure of a common sponge also makes it a breeding ground for bacteria.

Researchers at Duke University looked at 80 different strains of E. coli under various conditions. Different types of bacteria thrive in different settings—some are better suited to living with other species, while some prefer isolation. The research shows that environments that support both kinds of organisms nurture the most diversity. Examples include soil riddled with air pockets of different sizes—or a porous kitchen sponge.

After studying bacterial growth on a variety of plates with wells for the germs to nestle into, researchers recreated the experiment with a strip of sponge. The sponge grew a more diverse microbe population than any of the laboratory equipment they used. The holey material allowed organisms to either multiply in isolation or in the presence of other strains, depending on their needs.

The findings are a good reminder to replace your kitchen sponge if you haven't done so in a while. No matter how clean it looks, attempting to clean your plates with a weeks-old sponge may not have the intended effect. This still applies if you microwaved your old sponge or run it through the dishwasher, which can kill some germs while leaving more dangerous bacteria to multiply. Here are more surprisingly filthy items you use every day.