Microscopic Stowaways on the ISS
Living in a Microbial World
A 5000x scanning electron microscope image of E. Coli bacteria.
It is a normal resident of human intestines and provides vitamin
K and some of the B vitamins. Image Credit: The
Centre for Microscopy and Microanalysis
, The University
of Queensland, Australia.
Microbes are everywhere.
"Just stand and breathe, and you're releasing microbes," Roman said. "You
can wash and scrub and use antiseptic soap, and you'll still have
microbes on your skin. You have them everywhere: in your clothes,
on your skin, in your hair, in your body -- everywhere you could
Many people may find the thought of microbes living on and in their bodies
disturbing, but living with an entourage of stow-away microbes is natural.
"Generally speaking, microbes are invisible, and so people just don't think
of them as much as you do some other things," said Dr. Duane Pierson,
director of microbiology at NASA's Johnson Space Center.
"People need to be reminded that we live in a microbial world," Pierson said.
"They were here before us and they'll probably be here afterwards.
We co-exist with them very well..."
In fact, bacteria in people's intestines help to digest food, providing
some otherwise unattainable nutrients, such as vitamin K. A person's
resident microbes also actually protect them from infection by
competing with dangerous microbes looking for a place to grow.
While it is natural for a person to live with a host of resident microbes,
seven people -- each with their own set of microbes -- living
in a small, air-tight can for months or years is certainly not.
"When the crew goes up to the station, they'll each have their own microbial
flora, and when they return back, for the most part they've exchanged
that flora with each other," Roman said. Most of these exchanged
microbes are fought off by the crew's immune systems and their
own resident microbes, Pierson noted, but the potential for infection
The first step in protecting the health of the crew
is testing each crewmate for infection before launch. Only healthy
crew members are allowed to fly into space, and they're quarantined
before launch to prevent them from contracting harmful germs at
the last moment.