Stop. Drop the sponge and step away from the microwave.

That squishy cleaning apparatus is a microscopic universe, teeming with countless bacteria. Some people may think that microwaving a sponge kills its tiny residents, but they are only partly right. It may nuke the weak ones, but the strongest, smelliest and potentially pathogenic bacteria will survive.

Then, they will reproduce and occupy the vacant real estate of the dead. And your sponge will just be stinkier and nastier and you may come to regret having not just tossed it, suggests a study published last month in Scientific Reports.

(Readers wrote in with many questions about sponges. We answered a selection of them here.)

Bacteria are everywhere, so it’s no surprise that a kitchen sponge would be full of them. But previous research had underestimated a sponge’s quantity and range of bacteria. By looking at the DNA and RNA in samples from 14 used sponges that may be as dirty as the one sitting in your sink right now, Markus Egert, a microbiologist at the University of Furtwangen in Germany, and his team identified 362 different species of bacteria living within them. And the scientists were surprised to find how densely microbes occupied such close quarters: About 82 billion bacteria were living in just a cubic inch of space.

“That’s the same density of bacteria you can find in human stool samples,” Dr. Egert said. “There are probably no other places on earth with such high bacterial densities.”