Download At Exploration Park, Kennedy Space Center

Space Aeronautics Internship Program (SAIP)
At Exploration Park, Kennedy Space Center
1. Name of organization:
University of Florida, Dept. of Microbiology & Cell Science
2. Title of the project:
"Development of Antibiotic-Resistant Microbes During Human Space Flight"
3. Mentor: Dr. Wayne Nicholson
4. Abstract (500 words):
Summary: This summer project will provide an opportunity for the successful applicant to
participate in our current microbiology mission to the International Space Station (ISS). This
mission is scheduled for launch at the end of November 2013, on the third flight of the SpaceX
Dragon capsule to the ISS. The applicant will cultivate the test microorganisms in simulated
microgravity and measure their frequencies of mutation to antibiotic resistance vs. control
cultures incubated under identical conditions, but at Earth-normal gravity (1 xg).
Background: Maintaining astronaut health during long-term spaceflight is of prime importance
to the success of exploration missions to destinations such as near-Earth asteroids or Mars. The
immune system weakens during long-duration missions in Low Earth Orbit (LEO), rendering
astronauts more susceptible to infection. In addition, microgravity induces in certain bacterial
species increased virulence properties such as: adherence to mammalian cells, biofilm formation,
resistance to acid and macrophages, and antibiotic resistance. As part of the normal population
of microbial inhabitants on and within the human body, astronauts carry many microbes
considered “opportunistic pathogens”, i.e. normally harmless microbes with the potential to
cause disease in hosts with lowered immune function. Opportunistic infections are often treated
with combinations of antibiotics that differ in their mechanisms of action. Combination antibiotic
treatment is often used because (i) certain antibiotic combinations work synergistically to more
effectively combat the pathogen than either drug given alone, and (ii) the probability of the
pathogen developing resistance to two antibiotics simultaneously is much lower than that of
developing resistance to a single antibiotic.
Goal: We propose to test the hypothesis that exposure to the human spaceflight environment,
particularly simulated microgravity, increases the mutation frequency of resistance to the
commonly-used antibiotics rifampicin (RFM) and trimethoprim (TMP). As our test organisms
we will use two model Gram-positive bacteria: (i) Staphylococcus epidermidis, a harmless
human commensal organism closely related to the opportunistic pathogen Staphylococcus
aureus; and (ii) Bacillus subtilis laboratory strain 168, a harmless relative of pathogenic Bacillus
and Clostridium strains.
Central Objectives: We propose to:
1. Incubate parallel cultures of test organisms either at 1 xg or simulated microgravity;
2. Measure spontaneous mutation frequencies of B. subtilis and S. epidermidis to RFM or TMP.
3. Compare mutation frequencies obtained from the microgravity vs. 1xg control cultures.
4. Test single antibiotic-resistant mutants for development of dual drug resistance.
Methods: Microgravity and 1-xg liquid cultures will be propagated in a commercial clinostat in
10-ml High Aspect Ratio Vessels (HARVs) by rotation either parallel or perpendicular to Earth's
gravity field, respectively. Bacteria will be enumerated and plated on rich medium containing
RFM or TMP, colonies counted and mutation frequencies calculated. Singly-resistant mutants
obtained will then be screened for double resistance. If time allows, mutations will be identified
by PCR and nucleotide sequencing. All microbiology and molecular biology techniques
proposed are routinely performed in our laboratory.
Significance: Understanding multidrug resistance in opportunistic pathogens during long-term
human space flight directly benefits astronaut health and the success of extended missions both
in LEO and interplanetary space.
4. Expected student working hours: 8 hours per day, Monday-Friday.