A cyanobacterium species launched into low-earth orbit survived 10 days in an open container before being isolated in a terrestrial microbiology laboratory, according to microbiologist Karen Olsson-Francis of the Open University in Milton Keynes, United Kingdom, and her collaborators.  Not only does this outlandish isolation procedure suggest that at least some bacteria could endure longer journeys through space, a deeper look into the fortitude of this cyanobacterial species might yield some tips as to what it takes to maintain extraterrestrial settlements with populations of plants, animals, and humans. Meanwhile, details of the microbial experiments appear in the April Applied and Environmental Microbiology (76:2115- 2121).

The U.K. researchers isolated only a single species of bacterium from the terrestrial rock samples that contained an entire community when launched and that traveled for 10 tough days in orbit about 300 km above Earth. That cyanobacterial species, designated OU-20, can also be isolated from limestone cliffs along the English Channel-the same source for the rocks that were launched into space, Olsson-Francis says.

The less-well-traveled samples were subjected to desiccation and vacuum in the laboratory before OU-20 was isolated, she points out. Based on both culture and culture-independent methods (16S rDNA), the U.K. researchers also found evidence of other microbial species, including Pleurocapsales, Oscillatoriales, and Chroococcales, in the same rock samples. In terms of morphology, OU-20 resembles members of the genus Gloeocapsa, which are found in biofilms colonizing granite in Antarctica.

"This is the first time that a novel organism has been isolated after exposure of a microbial community to outer space conditions," says Gerda Horneck of the DLR German Aerospace Center, Institute of Aerospace Medicine. This is also the first investigation that used low-earth orbit to select for extremophiles, adds Olsson- Francis. The flight subjected the microbes to extremes of temperature, low pressure, cosmic radiation, and microgravity. The experimental container, called a Biopan, was closed before the orbiter landed to protect the experiments from the heat of re-entry. The research was conducted with space applications in mind. The investigators chose the location where rocks were harvested, which is submerged in seawater at high tide, for its presumed diversity, in the hope of discovering novel, space-hardy species.  Insights from these experiments could have applications for long-term space flights and extraterrestrial settlements in terms of determining requirements for "oxygen, fuel, and biomass production; nutrient acquisition, biomining; and feedstock provision," according to Olsson-Francis and her collaborators.

These research findings confirm earlier observations that bacteria, cyanobacteria, and lichens survive shortterm space flights, suggesting that "lithopanspermia may occur within a solar system," says Rocco Mancinelli of the SETI Institute in Mountain View, Calif., referring to the hypothesis that life spreads through outer space when hardy seedlings travel on rocks from one celestial body to another. The cyanobacteria likely survived their time in orbit in part because the rocks in which they were embedded protected against damage from ultraviolet (UV) light, Mancinelli says. "The real factor affecting survival is extreme desiccation. This study seems to have selected for the organism that could best withstand desiccation in the space environment." Olsson-Francis and her collaborators note that a thick, mucilaginous sheath, which can be observed via transmission electron microscopy, is also important for protecting dense colonies of OU-20 against UV light and other environmental insults.

The research confirms the value of exposing microorganisms to conditions in space exposure instead of depending on ground-based simulations, says Daniela Billi of the University of Rome, Italy. Adds Silvano Onofri of the University of Tuscia at Viterbo, Italy, these microbial findings "could modify the general perception of the central role of our planet in the origin of life."

David Holzman
David Holzman is the Microbe Journal Highlights Editor.