On long space flights, normally harmless bacteria could mutate in unforeseen ways and threaten the crew鈥檚 health or the life-support systems 鈥� so NASA is developing a 鈥済ene chip鈥� to identify such menacing microbes en route.
Most bacteria found on spacecraft have been carried aboard by the crew. On extended missions, the crew will have to grow plants and recycle waste, water and air, providing unique ecological niches in which the bugs could flourish.
On Earth, species that cause disease or other problems tend to be well known and behave in familiar ways. But in the alien conditions of near-zero gravity and increased radiation, little-known bugs might become virulent, and even familiar species could start behaving differently, for example clogging up air filters or water purification systems.
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There is evidence to support this concern. Simulated microgravity experiments have shown that Salmonella bacteria become more virulent. And George Fox of the University of Houston, Texas, and his team have found microgravity causes changes in gene expression in E. coli bacteria. 鈥淚f [a microorganism] for some reason is causing a problem, we need to have a mechanism of figuring out what it is,鈥� he says.
Unique signatures
Bacteria can be identified using probe DNA sequences that each bind only to a specific species. But it would be impossible to carry probes for every possible bacterium that could mutate. So Fox and his colleague Richard Willson have developed a means of quickly identifying which group of microorganisms a mystery bug belongs to.
Instead of DNA, they look at portions of the bacteria鈥檚 ribosomal RNA. These regions are highly variable, and groups of related bacteria have unique signature sequences. The researchers are building a chip that will incorporate 4000 RNA probes, carefully chosen to cover a wide range of bacteria.
Although the chip cannot pinpoint the exact organism, if a mystery microbe鈥檚 signature matches any one of the probes, the astronauts will know roughly what they are up against.
鈥淚t doesn鈥檛 have the yes-no answer of the single-target probes,鈥� says Willson. But it would almost always provide at least some information 鈥� suggesting which antibiotics might be effective, for example.
Front-line biodefence
Duane Pierson, director of microbiology at NASA鈥檚 Johnson Space Center in Houston, agrees. He says that while bacterial infections in space have not caused astronauts any major problems so far, they remain a concern.
鈥淚f you are going to Mars, you don鈥檛 want to have to send somebody back because of some sort of infection which could have been prevented if we understood more about it,鈥� he says. 鈥淭his technology could be very valuable.鈥�
The gene chip could also help on Earth. For instance, in front-line biodefence, it could quickly identify whether a suspicious powder in an envelope is a microbe or just sugar.
And in cases of infectious diseases, if clinicians are unable to identify the exact organism, despite clear signs of infection in a patient, the chip could at least narrow things down. 鈥淭his is a way of getting a clue about the puzzling cases,鈥� says Willson.