Attention at all passengers. You can now book your train tickets on Uber and get 10% back in Uber credits to spend on your next train journey.

So no excuses not to visit your in-laws this Christmas.

Trains now on Uber. T's and C's apply check the Uber app. This is a scientific American 62nd science. I'm Eileen Augenbrand.

Our microbiomes, the tiny organisms that live on us and in us, can influence our health.

And a recent study looked at microbiome composition and diversity depending on where and how

we live.

Given the same latitude and climate across South America.

We found in a gradient of urbanization

from jungle houses, hats of Amerindian people living traditional lifestyles, all the way to a modern city like Manaus was differences in microbes from our houses and from our skin and differences

in exposure to chemicals.

Microbiologist Maria Gloria Domingas Beo from Rutgers University.

She and her colleagues collected samples from people, pets, and spaces in homes, like the kitchen, bathroom, and bedrooms.

They analyzed bacteria, fungi, parasites, and chemicals.

And they found two trends as you go from the rainforest, to a farm to a town to the city of Manaus.

With increasing population density, we are exposed to a higher diversity of fungi.

We carry more diversity of fungi in our skin, but in our gut we lose microbial diversity.

The study is in the journal Nature Microbiology.

Urban homes use more chemical cleaners than do rural or rainforest homes, and they're more likely to be built out of synthetic materials.

So city residents are burdened with more chemicals, including metabolites of cleaners, detergents, and

paints in and on their bodies.

In addition, the microbes of urban dwellers are far more like each other than they are like

the more healthful mix found in the rainforest.

...