lundi 18 juin 2018

Investigation Tests BEST Method of DNA and RNA Sequencing










NASA - Genes in Space logo.

June 18, 2018

Much of present-day science focuses on exploring the molecular world. A primary tool is DNA sequencing, performed for the first time on the International Space Station in August 2016.

International Space Station (ISS). Animation Credit: NASA

An investigation now aboard the space station, Biomolecule Extraction and Sequencing Technology (BEST), seeks to advance use of sequencing in space in three ways: identifying microbes aboard the space station that current methods cannot detect, assessing microbial mutations in the genome because of spaceflight and performing direct RNA sequencing. All use compact tools, including the MinION miniature sequencer, already proven to work onboard the space station.

The remoteness and constrained resources of living in space require simple but effective processes and procedures to monitor the presence of microbial life, some of which might be harmful. A previous investigation, Genes in Space 3, performed in-flight identification of bacteria on the station for the first time. BEST takes that one step farther, says principal investigator Sarah Wallace, identifying unknown microbial organisms using a swab-to-sequencer process rather than a traditional culture-based technique. “That way, we can identify microbes that cannot be detected using traditional culturing methods, and we aren’t increasing the number of potential pathogens that might be present on the station,” Wallace explained.


Image above: Biomolecule Extraction and Sequencing Technology (BEST) seeks to advance use of sequencing in space via three objectives: identifying microbes aboard the space station that current methods cannot detect, assessing microbial mutations in the genome because of spaceflight, and performing direct RNA sequencing. Pictured above are Sarah Stahl and Christian Castro, microbiologists on the project. Image Credit: NASA.

For the second objective, researchers plan to compare full genome sequences from multiple generations of a model organism grown on the space station against those from the same organism grown in parallel on Earth. “This can provide insight into mutation rates in low-Earth orbit,” said project manager Kristen John.

Finally, BEST demonstrates the process of direct RNA sequencing, which opens new avenues for in-flight research. Researchers found that organisms respond to spaceflight by making transcriptomic changes, changes in RNA or gene expression. Sequencing RNA defines what genes are turned on and off, which is important for understanding how life adapts to spaceflight.

“Because the MinION detects changes in current, it can directly sequence RNA as well as DNA,” said co-investigator Aaron Burton. “With most other platforms, you first have to convert RNA to DNA, and this additional processing could bias your data, causing you to miss what’s really going on. Direct RNA sequencing results in near real-time gene expression data.”


Image above: The MinION miniature sequencer and the miniPCR, both compact tools used aboard the space station. Image Credit: NASA.

“With small modifications to our process, you can pretty much do any type of sequencing on the station,” said Wallace. “Until now, we had to bring samples back to the ground to see these changes. We know gene expression changes, but freezing a sample and bringing it back to the ground could result in alterations not caused by the spaceflight environment. If we could look at it while on the station, it might look very different. There is so much to be gained from that real-time snapshot of gene expression.”

The investigation’s DNA and RNA sequencing components provide important information about the station’s microbial occupants, including which organisms are present and how they respond to the spaceflight environment -- knowledge that will help protect humans during future space exploration. The validation of direct RNA sequencing has the potential to be a game-changer for research into crew health by eliminating the need for conversion and bias it may introduce. Knowledge gained from BEST also can be implemented to provide new ways to monitor the presence of microbes in remote locations on Earth.

Related links:

Biomolecule Extraction and Sequencing Technology (BEST): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7687

Genes in Space 3: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7448

Spot the Station: https://spotthestation.nasa.gov/

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Animation (mentioned), Images (mentioned), Text, Credits: NASA/Michael Johnson/JSC/International Space Station Program Science Office/Melissa Gaskill.

Greetings, Orbiter.ch

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