Space Bacteria!

Pseudomonas aeruginosa, fresh from outer space

Not really space bacteria, but terrestrial bacteria that have been sent into space. This article comes to us via, which details research recently published in Applied and Environmental Microbiology, and details some work examining the response of microorganisms exposed to microgravity conditions aboard the Space Shuttle.

Pseudomonas aeruginosa, seen in an electron micrograph to the left, is a Gram negative bacterium that is very prevalent in the environment. The organism is benign in immunocompetent individuals, but is a potent opportunistic pathogen and a significant cause of nosocomial infections. The bacterium is particularly a problem as a cause of broken skin infections, is a primary complication of burn victims, and is the primary cause of death in patients with the genetic disorder cystic fibrosis.  One notable and surprising case of Pseudomonas aeruginosa infection was astronaut Fred Haise, who became sick with the bacterium during the Apollo 13 spaceflight in 1970. You may remember him as the astronaut played by Bill Paxton in the very exciting movie about the mission. The case was notable because Mr. Haise was a very healthy individual with no underlying predispositions to disease, but became progressively sicker during the mission. He recovered after the astronauts safely made it back to Earth. 

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Researchers at Arizona State University were interested in the effects of microgravity on microorganisms, and cultures of P. aeruginosa and Salmonella enteica were sent into Earth orbit as part of the STS-115 space shuttle mission.  The scientists examined what genes were turned on and which were turned off as the organism was grown aboard the spacecraft, and correlating those changes with changes in virulence of the organisms.  They found that over 167 genes showed altered levels in bacteria grown on the space shuttle in comparison with Earth-bound control organisms, and that the Hfq gene appeared to be a master regulator of space-flight induced changes.

The researchers have hypothesized that the changes that occur during microgravity conditions onboard the spacecraft mimic key conditions that they would encounter during the early stages of infection in the human body, due to the low levels of fluid force on the surfaces of the bacterial cells.  In fact, the low gravity conditions onboard the spacecraft actually appear to increase the virulence of these organisms, potentially explaining why Fred Haise became sick with what should have been an innocuous microorganism during the Apollo 13 mission.

BONUS: Based on what we know about the process of disease, what are some other possible reasons that astronaut Fred Haise became sick with this organism in 1970?


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on March 29, 2011, in A bit 'o history, Bonus!, Microbes in the News. Bookmark the permalink. 6 Comments.

  1. Steph Weakland

    The changing conditions (especially in relation to gravity) may have altered the normal microbiota in Haise’s body. Since Pseudomonas aeruginosa is a “potent opportunistic pathogen,” it may have taken advantage of that and found a newly suitable environment in which to grow.

    • I like this! The interplay between host and normal microbiota in freefall is likely going to be different than in normal gravity conditions. If the normal microbiota are at a disadvantage, an opportunistic pathogen may get an advantage for growth.

  2. Rachel Florance

    The lack of gravity could have caused his immune system to weaken making it easier for pathogens to enter especially Pseudomonas aeruginosa because it only causes diseases in individuals who have weaken immune systems.

    • Medicine in microgravity conditions has all come from a very limited set of studies of astronauts and cosmonauts on board the US, Russian, and International space stations. There is therefore not a lot of data to support any conclusions. I did note that the Wikipedia page on weightlessness indicates: “Other significant effects include fluid redistribution (causing the “moon-face” appearance typical of pictures of astronauts in weightlessness), a slowing of the cardiovascular system, decreased production of red blood cells, balance disorders, and a weakening of the immune system.”

  3. Could it be because Pseduomonas aeruginosa is an aerobic organism. So in the space shuttle the air may have a high content of oxygen, which would cause a higher growth rate of the microorganism. And if it is growing more frequently and the normal microbiota is slightly inhibited, it could cause the infection to occur.

    • I don’t know if the oxygen content is relevant. I did some quick Googling, and found this page from Yale University, which says that on the Space Shuttle, astronauts breathe a mixture of 20% oxygen/80% nitrogen gas, which has a slightly lower concentration of oxygen that sea level on Earth. Most kids today may not be aware of a tragic accident prior to the successful Apollo moon missions, which was a test mission in June 1967. An accident several weeks prior to the scheduled launch led to the deaths of all 3 astronauts in the spacecraft command module in a cabin fire. It was this accident that led to the shift from using pure oxygen in the cabin to a mixture of oxygen/nitrogen to diminish the fire risk.

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