Dust buildup can become pesky for those of us in charge of cleaning it off the shelves, tables, and windowsills. Within dust are invisible bacteria and fungi that not only collect on our windows, but can also provide a window into our homes. According to a recent study published in the journal Proceedings of the Royal Society B, the bacteria and fungi in dust can reveal our geographic locations, pets, and gender.

There are thousands of microbial species crawling around our homes. "Every day, we're surrounded by a vast array of organisms in our homes, most of which we can't see," said Noah Fierer, co-author of the study and associate professor in the Department of Ecology and Evolutionary Biology at CU-Boulder, in the news release. "We live in a microbial zoo, and this study was an attempt to catalog that diversity."

Some of these microbes could have a negative effect on our health, while others could actually be beneficial because they can help children develop healthy immune systems and prevent allergies later on in life. In order to get a better understanding of how microbes can influence our health, Fierer and his colleagues led the project Wild Life of Our Homes, where they collected dust from a spot we all overlook when cleaning — the top of door frames. Fungal and bacterial communities were collected from inside and outside about 1,200 homes located across the U.S. These homes represented a broad range of home designs and spanned many climatic zones.

The findings revealed there were more than 125,000 kinds of bacteria and 70,000 types of fungi across all the homes in the study. The average household had more than 5,000 different species of bacteria and about 2,000 different species of fungi. When the researchers compared indoor and outdoor microbes, they found indoor bacteria and fungi to be more diverse than those found outside. This is because many outdoor species were being brought into households.

Indoor microbes were influenced by people, home, and pets. The geographic location of the participants’ homes influenced the makeup of indoor fungi.

"Geography is the best predictor of fungi in your home," Fierer said. "The reason is that most fungi blow in from outdoors via soil and leaves." For example, a home in the upper Midwest, for instance, will harbor distinct fungi compared to a home in the Southeast.

The researchers also revealed the type of bacteria found inside the home varied according to who lived there — the ratio of men to women. Corynebacterium and Dermabacter, two kinds of skin bacteria, were commonly found in homes with more men. Roseburia, a type of bacteria found in human feces, was more common in homes with more men. These variations in bacteria are attributed to differences, including skin biology and hygiene practices between men and women.

Households that contained pets also influenced the different types of bacteria found. For example, 56 different types of bacteria were more abundant in households that owned dogs, and 24 types of bacteria more abundant in households of cat owners.

"One of the key takeaways is that if you want to change what you breathe inside your house, you would either have to move very far away or change the people and the pets you live with," said Albert Barbaran, lead author of the study and a graduate researcher in CU-Boulder's Department of Ecology and Evolutionary Biology, in the news release.

The findings help us understand the bacteria and fungi that takes residence in our homes, which can reveal how our living environment affects our overall health and well-being. There is more to be revealed since there are still tens of thousands of bacteria that no one knows about, nor do they have names. This is extremely vital, since we spend a lot of our time indoors while the bacteria in our homes increases.

Source: Barberan A, Dunn RR, Reich BJ et al. he ecology of microscopic life in household dust. Proceedings of the Royal Society B. 2015.