Which Household Item Is the Best Incubator for Bacteria?

Scientists found that kitchen sponges are a better environment for growing diverse bacteria than laboratory petri dishes.

Kitchen sponges are meant for cleaning, but just how clean are they? According to Duke University researchers, because sponges are typically porous, damp, and filled with food particles, they are the perfect place for bacteria to live and thrive – and they can hold 54 billion bacteria per cubic centimeter (.06 cubic inches). Different types of bacteria can thrive in different holes in a sponge, since the holes range in size. Some bacterial strains prefer isolation, whereas others thrive in more "social" environments. Through testing, the researchers learned that a sponge's bacterial community is more diverse than bacterial communities in liquid cultures, such as those developed in laboratory settings. Although most of the bacteria that inhabit kitchen sponges are relatively harmless, that's not necessarily always the case. In fact, sponges can serve as ideal breeding grounds for bacteria such as Salmonella. “Sponges are not really well-suited for kitchen hygiene,” said Markus Egert, a microbiologist at Furtwangen University in Villingen-Schwenningen, Germany. “There’s hardly any sterile surface at home, but the kitchen sponge is probably the most densely populated item at home.” Fortunately, by simply switching your sponge for a brush, you can make your cleaning implement much less hospitable to bacterial invaders. Bacteria basics: A single gram (.035 ounces) of soil contains about 40 million bacteria. The average human has roughly the same number of normal body cells as bacterial cells. Bacteria are the oldest-known life form, having survived on Earth for 3.5 billion years.