Bug Busters -- Space Station Research Could Help Prevent, Treat Food Poisoning03.11.09
Astronaut Heidemarie M. Stefanyshyn-Piper, STS-115 mission specialist, works with the Yeast-Group Activation Packs on the middeck of space shuttle Atlantis. Image Credit: NASA
Germs are virtually everywhere on Earth and it’s natural that they would stow away for the ride into space when humans go there. New NASA research shows some of those germs, or microbes, are more infectious after spending time in “zero-gravity.”
While that may sound like a bad thing – and certainly it is a challenge that needs to be met to keep astronauts healthy – there is a silver lining. Using spaceflight studies to understand the mechanism for this increased virulence could help us develop new strategies for fighting the spread of such disease-causing microbes here on Earth.
"This research opens up new areas for investigations that may improve food treatment, develop new therapies and vaccines to combat food poisoning in humans here on Earth, and protect astronauts on orbit from infectious disease," said Julie Robinson, program scientist for the International Space Station.
Experiments with Salmonella were flown on shuttle missions to the International Space Station in September 2006 and March 2008. The 2006 experiment surprisingly showed that the spaceflight environment causes a short-term alteration in Salmonella virulence. The 2008 experiment demonstrated that a change in growth media controls the virulence effect. There is no evidence that the space-grown bacteria sustain these effects long-term upon return to Earth.
Cheryl Nickerson, a scientist at Arizona State University's Biodesign Institute, led a research team that investigated the importance of the microbial growth medium to gene expression and virulence during spaceflight. Image Credit: The Biodesign Institute, Arizona State University
Salmonella is a leading cause of food poisoning and related illnesses, and their unpleasant effects on our digestive systems are well documented. In the U.S. alone, according to the Centers for Disease Control, 1.4 million non-typhoidal Salmonella infections resulted in 168,000 doctor’s office visits annually from 1996–1999. Salmonella infections caused 15,000 hospitalizations and 400 deaths in each of those years. Recently, Salmonella has been in the news as the agent responsible for infectious disease outbreaks in the U.S. linked to contaminated food products like peanut butter that have sickened thousands of individuals and caused several fatalities.
Bacteria like Salmonella use an amazing array of techniques to outwit the human body’s defense mechanisms and cause illness. By changing their gene expression, they adapt to different environments to alter their disease-causing potential or virulence.
Although the study of factors related to microbial virulence is now well advanced, many key pieces of the puzzle still are missing. Cheryl Nickerson, a researcher in the Center for Infectious Diseases and Vaccinology at Arizona State University’s Biodesign Institute, led the team that investigated the effect of spaceflight on Salmonella on both space flights. The 2006 experiment was the first to identify the molecular “switch” that activates the increased the virulence of Salmonella caused by spaceflight. The follow-up experiment in 2008 showed that adjusting the ion content of the bacteria’s growth medium can be used to turn off the increase in Salmonella virulence observed in space. Nickerson’s initial findings, published in the Proceedings of the National Academy of Sciences, and her collective findings, published in the journal PLoS ONE, hold promise for new strategies to combat Salmonella food-borne infections.
These space experiments helped researchers show that a mechanical force known as “fluid shear,” which is the motion of fluid that cells sense as they pass over a surface, could have a dramatic effect on Salmonella's disease-causing potential. Lower fluid shear conditions, it turns out, are found both in microgravity and in our intestines. The bacteria cultured in space are more virulent, and Nickerson’s work showed that by modifying the medium in which the cells are grown, the virulence could be reduced or turned off.
Astronaut Heidemarie M. Stefanyshyn-Piper, STS-126 mission specialist, works with the Microbe Group Activation Pack containing eight Fluid Processing Apparatuses on the middeck of space shuttle Endeavour while docked with the International Space Station. Image Credit: NASA
In other words, space travel may trick the bacteria into behaving as though they were in the low fluid shear environment of the intestine, essentially turning on a switch inside the microbe that increases virulence. Changing the chemistry of the medium in which the bacteria are cultured reverses this effect.
This research opens up new opportunities to improve food treatment methods, develop new therapies and vaccines to combat food poisoning in humans here on Earth, and help better protect astronauts in space from infectious disease.