Household microbe menagerie

A study shows that the average American home contains about 9,000 different species of microbes, including 2,000 types of fungi and 7,000 varieties of bacteria.

Volunteers from across the country sent samples of dust from the ledges above their doorways, which are often overlooked during cleaning, to scientists at the University of Colorado at Boulder, according to BBC News. Researchers found that the types of microbes present varied depending on where the house was located, who lived there and whether the owners had pets.

The researchers said they're now interested in how the presence of microbes affects human health. Some are linked to allergies and disease, they said, but most are harmless and others may be beneficial.

“It is just a fact of life that we are surrounded by these microbes,” said lead author Dr. Noah Fierer.