This experiment will evaluate how exposure to space leads to genetic changes and variation using model microbe cultures.Principal Investigator(s)
Bionetics Corporation, Cape Canaveral, FL, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration:
April 2006 - April 2007Expeditions Assigned
13,14Previous ISS Missions
This will be the first mission for the POEMS investigation.
The Passive Observatories for Experimental Microbial Systems (POEMS) investigation was designed to demonstrate a passive system for microbial cultivation in the microgravity environment. The secondary objective of
POEMS was to observe the generation and maintenance of genetic variation within microbial populations in microgravity.
POEMS supported experiments that determined the growth, ecology, and performance of diverse assemblages of microorganisms in the microgravity environment. These studies of microorganisms are required for maintaining human health and bioregenerative function in support of NASA Exploration Systems requiring Advanced Life Support. For this experiment, replicate cultures were inoculated on the ground and launched onboard the Space Shuttle. Half the cultures were returned at the close of the Shuttle mission; the remaining cultures were transferred to the ISS where they were preserved (frozen) at successive time-points over the course of six months. The cultures were returned to Earth and compared to ground controls in order to determine how microgravity affected the physiology and genetic composition of the microorganisms.
Bacillus subtilis was introduced by a small liquid inoculum into the void volume of an Opti-cell during preflight integration, thereby providing a uniform inoculation front to the semi-solid media. Bacterial growth proceeded in a planar fashion down the long axis of the culture chamber, thereby providing a physically traceable chronology of bacterial growth during flight. As bacteria propagate through the media, they encountered genomic DNA from related Bacillus species that have been marked with an antibiotic resistance gene. Some cells have the capability to bind, transport, and recombine the DNA via transformation. By assimilating the resistance marker, these transformants naturally obtain a competitive advantage in the selective medium. The rate and extent of genetic transformation during growth in flight is compared to ground controls. Genetic and physiological screening of isolates identifies changes during flight in vegetative cells. If cells form spores during flight due to nutrient exhaustion or other environmental stresses, spores are isolated for analysis. Post-flight analyses seek to understand the effects of spaceflight on DNA repair mechanisms, the ability to assimilate exogenous DNA, and the ecology of a diversifying assemblage of bacteria cells in the space flight environment.
Extension of human habitation into space will result in humans carrying with them the microorganisms with which they coexist on Earth. This proposal seeks to develop simple, ground-based experimental systems with low manpower, mass, volume, and energy requirements that will enable exploration of the ecology and evolution of microbiological communities in the space environment. Given the potential for rapid change in populations of microorganisms under space conditions, it is essential to the NASA mission to understand both the mechanisms and consequences of microbial evolution in space. Just as on Earth, the survival of humans on long-term missions is inextricably linked to their microbial companions. Passive experimental microbial systems (POEMS) are an enabling technology to address fundamental questions in the ecology and evolution of microbes in the insulated ecosystem of the space environment.Earth Applications
The research objective is to develop and test passive observatories for experimental microbial systems (POEMS) for the long-term, multi-generation monitoring of microbial community development in isolated biological systems such as humans on long-term space missions. However, the results of this study may be applicable to other isolated biological systems found on earth, including those that incorporate humans, such as cruise ships and submarines. Results may also provide insight into the mechanisms of DNA repair and acquisition of exogenous genetic information in microorganisms, which is important to understanding the spread of such genetic-based traits as antibiotic resistance.
POEMS is a passive investigation that will only require the crew to perfom payload transfers.Operational Protocols
POEMS does not require crew time or power on ISS. The crew will transfer the payload from the Shuttle to ISS, and then back to the Shuttle following the end of the investigation. Samples will be returned to researchers for analysis on Earth.
Ten POEMS canisters launched on STS-121 in a middeck locker (ambient environment). As a passive, sortie experiment, five canisters were returned on the same shuttle flight and represent a data point for approximately eleven - twelve days of exposure to space flight. The remaining canisters were transferred to an ambient location on the ISS. Of these, three canisters were successively transferred into the Minus Eighty Degree Laboratory Freezer for ISS (MELFI) freezer and maintained at -68°C (-90°F) or colder. Two of the frozen canisters returned home on STS-115, and the third on STS-116, as well as one of the ambient canisters, returned on STS-116.
POEMS performed as expected, and data (temperature, thermal offsets and humidity) has been recovered from data-loggers. Bacterial cells and genetic transformants were recovered in all returned canisters. Fixed gases and volatile organic compound analyses of canister headspace are underway.
The investigation team continues to isolate and characterize rifampicin-resistant bacteria and to enumerate auxotroph mutants (lysine methionine tryptophan) that were recovered from sortie mission canisters (five canisters) and three canisters from the ISS mission returned on STS-115. Viable cell and spore counts are completed; total direct counts and genetic characterization of transformants is on-going. Transformation efficiency was lower than expected in both flight and ground experiments, but rates were sufficient to yield >102 rpoB transformants. Data analysis will continue for six months after recovery of all POEMS canisters from ISS.
Trends in early analyses suggest that microbe population densities and transformation rates may be slightly elevated in flight samples compared to ground controls, but the preliminary conclusion is that the effects of the space environment on the rate of horizontal gene transfer are not statistically significant for Bacillus subtilis. Full data analysis is pending. (Evans et al. 2009)
Reed DW, Rodriguez JI, Roberts MS. Passive Observatories for Experimental Microbial Systems (POEMS): Microbes Return to Flight. 34th International Conference On Environmental Systems, Colorado, Springs, CO; 2005 July