Lethal Bacteria Turn Deadlier After Space Travel

Graeme Stemp-Morlock
for National Geographic News
September 24, 2007

Bacteria can change into more infectious and deadly organisms after a stint in space, a new experiment suggests.

A science experiment on board space shuttle Atlantis in 2006 included Salmonella typhimurium bacteria, which is often fatal in humans.

When the bacteria—which had been safely isolated from the space crew—returned to Earth, scientists injected them into mice.

They found the space-faring bacteria caused death quicker and more often than Earth-restricted organisms.

The findings are concerning for future astronauts who will embark on longer space missions farther away from Earth-based medical help, experts say.

Genetic Transformations

Cheryl Nickerson is an associate professor of microbiology at Arizona State University's Biodesign Institute and lead author of the study.

Nickerson wanted to see if space's low-gravity environment would affect Salmonella. Usually a culprit in food poisoning, the bacteria can cause vomiting, fever, diarrhea, and abdominal cramps. Most types of Salmonella, which can grow on most foods, are fatal in the elderly or young if left untreated. (Related news: "Food Bacteria More Drug-Resistant in U.S., Europe, Study Suggests" [August 7, 2006].)

When the bacteria returned to Earth, genetic sequencing showed that 167 genes and 73 proteins had been altered.

One protein, called Hfq, helped control more than a third of the altered genes. Hfq regulates RNA—the code of bacterial life—during stressful events. When activated, the protein previously had been shown to strengthen several types of pathogens.

An technique called scanning electron microscopy also showed some Salmonella were starting to form biofilms, a protective slime layer.

On Earth, biofilms can grow on ship hulls and clog pipes, costing industry billions of dollars. Biofilms also worsen some diseases and reduce the effectiveness of many antibiotics.

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