Paving the Way to the Stars

IITRI Microbiologist Compares Effects of Modeled Microgravity Systems on Bacterial RNA Expression

"The meek shall inherit the Earth; the rest of us will escape to the stars," a Trekkie T-shirt proclaims. While we may not be colonizing Mars any time soon, one thing we know for certain is that when humans (or animals or plants) do travel into space, they'll be taking bacteria with them, creating concerns that go beyond rocket science.

	"It is purely practical research from the space life sciences perspective because it means people will be able to stop wasting time and money on experiments with improper controls." Margaret Juergensmeyer, Ph.D. IITRI microbiologist leading NASA study

It is simply not possible to send humans or animals into space without bacteria, and bacteria behave differently in space than they do on Earth. The question space life scientists seek to answer is, 'how are they going to behave differently, and is it something we have to protect against?' What astronauts can expect from these miniscule stowaways is knowledge best learned ahead of time.

Effects of Microgravity Still Up in the Air

Scientists currently know relatively little about how living organisms respond to microgravity (10^-6 to 10^-9 x g, or one-millionth to one-billionth of the gravity we feel on Earth), a characteristic of the space flight environment. The astronomical cost of space flight alone makes the advance of space life sciences painfully slow.

To compensate, scientists have developed modeled microgravity systems to simulate the near-weightlessness of space flight. To validate these systems, however, further experiments need to be conducted in space so that the data can be compared. Such comparisons have been done, but with a limited number of repetitions, making it difficult to confirm results. Several modeled microgravity systems have been used, but the precision to which they mimic the space environment is both variable and questionable. A truly reliable modeled microgravity system has yet to be identified.

Modeled Microgravity Systems Studied

IITRI has received a grant from the National Aeronautics and Space Administration (NASA) to help solve that mystery. "What we're doing is looking at the ability of modeled microgravity systems to change RNA expression in bacteria," said IITRI microbiologist Margaret Juergensmeyer, Ph.D., who is leading the project. The team, consisting of Dr. Juergensmeyer, her mother and colleague Elizabeth Juergensmeyer, Ph.D., of Judson College in Elgin, IL, and Evelyn Mobley, Ph.D., is examining data generated from four different modeled microgravity systems:

• Slow clinostat: the original modeled microgravity system. A cylinder turning at a rate of one-quarter revolution per minute (rpm), the slow clinostat randomizes the gravity vector affecting organisms contained within the cylinder. Instead of just pulling down, gravity pulls from all directions during the rotation of the sample.

• Fast clinostat: revolves at a rate of 60-80 rpm. This system, in addition to randomizing the gravity vector, also creates an extreme low shear environment at the very center of the sample, meaning that there is no convective action (i.e., heat does not rise) and minimal mixing of substances that come in contact with each other, similar to the space flight environment.

• Vibrational accelerator: mimics the vibration generated by machinery used in the space craft. Without the pull of gravity to eclipse its effect, vibration is the most dominant force in space flight.

• High Aspect Rotating Vessel (HARV): originally developed for space flight to aerate cultures, this system creates an extreme low shear environment, very similar to that found inside mammalian organs and tissues, and also very similar to that found during spaceflight. Dr. Juergensmeyer's team will begin working with the HARV system in late 2005.

Changes in RNA Expression Compared

The team is examining the effects on these systems on a harmless strain of Escherichia coli (E. coli), a universal mammalian intestinal organism. RNA samples from bacteria exposed to each of the four modeled microgravity systems will be analyzed using microarray techniques to identify differences in patterns of gene expression.

The quantity of specific mRNAs produced by a cell indicates which genes are expressed, or which genes have increased or decreased levels of expression. These data may provide insights into how the cell adapts to survive in its new environment.

Patterns Indicate Cellular Responses

"By looking at the RNA levels, we can start picking out trends, and that will give us an idea what the cell is experiencing, what stressors it might be feeling and how it might need to respond to its particular environment," Dr. Juergensmeyer explained.

By obtaining RNA expression data from bacteria exposed to each of the modeled microgravity systems under investigation, the team will create a baseline against which space flight data gathered in a future project can be compared. Once these baseline results are compared to data obtained from bacteria subjected to actual space flight, the modeled microgravity system most accurate for simulating the effects of space flight will become clear.

Findings to Cut Cost of Further Study

"It is purely practical research from the space life sciences perspective because it means people will be able to stop wasting time and money on experiments with improper controls," Dr. Juergensmeyer said. "Plus, with NASA scaling back on life sciences funding, people will be able to conduct studies on the ground at lower cost than in space flight, so it will allow more work to be done."

The knowledge gained from this work, and the protective measures it ultimately will afford, will help to pave the way for humankind's exploration of the stars.