RESULTS
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 (5 canisters) and
3 canisters from the International Space
Station (ISS) mission returned on STS-115.
Viable cell and spore counts are
completed; total direct counts and
genetic characterization of transformants
is ongoing. Transformation efficiency was lower than expected in both flight and ground
experiments, but rates were sufficient to yield >102 rpoB transformants. Data analysis
continues for 6 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.
PUBLICATION(S)
Roberts MS, Reed DW, Rodriguez JI. Passive observatories for experimental microbial systems
(POEMS): Microbes return to flight. 34th International Conference on Environmental Systems,
Colorado, Springs, CO; July 2005.
This investigation is complete; however additional results are pending publication.
ISS013E64639 - Image on the left shows ground control
and a flight sample of bacteria cultures growing through the
solid media agar, and scientists can sample the genetic
changes across multiple generations by sampling different
places in the growth medium. Image on the right shows
NASA International Space Station Science Officer, Jeff
Williams inserting one of the Passive Observatories for
Experiments Microbial Systems samples into the Minus
Eighty-Degree Laboratory Freezer for ISS freezer.