Movement is one of the clearest signs of life. Researchers at TU Berlin have now discovered that certain microbes react specifically to a chemical substance and actively move toward it—a principle that could help detect life on other planets in the future. Their findings could significantly change space missions, as the new method is not only simple, but also fast and cost-effective.
The team led by Dr. Max Riekeles from the Astrobiology research group at TU Berlin has demonstrated that the targeted movement of microorganisms can be used as a biosignature. The scientists examined three different types of microbes – two bacteria and one archaeon – and found that they all move towards the amino acid L-serine. This movement, known as chemotaxis, is a response to chemical stimuli and helps microbes locate food sources.
"Our results suggest that microbial movement could be a valuable method for detecting life on other planets," explains Max Riekeles. "Especially if life on Mars has a similar biochemistry to that on Earth, L-serine could serve as an attractant." This means that a simple test based on microbial movement could provide evidence of life without the need for complex chemical analyses.
Robust microorganisms as a model for extraterrestrial life
The microorganisms studied were specifically selected for their resistance to extreme environmental conditions. The highly motile bacterium Bacillus subtilis can survive temperatures up to 100 °C in spore form. Pseudoalteromonas haloplanktis was isolated from Antarctic waters and thrives at temperatures ranging from -2,5 °C to 29 °C. The archaeon Haloferax volcanii belongs to a group similar to bacteria but genetically distinct from them. It lives in highly saline environments such as the Dead Sea.
"Bacteria and archaea are two of the oldest life forms on Earth, but they move in different ways and have evolved motility systems independently," explained Riekeles. "By testing both groups, we can make life detection methods for space missions more reliable." The researchers used the amino acid L-serine to make the microbes move. Previous studies have shown that L-serine is a chemotactic stimulus for many organisms from all domains of life. L-serine is also suspected to exist on Mars. If life there has a similar biochemistry to that on Earth, it is conceivable that L-serine could attract potential Martian microbes.
The research team developed a simplified testing method based on a two-part chamber with a membrane. Microbes are placed on one side, while L-serine is inserted on the other. If the microbes are alive and mobile, they swim through the membrane to the food source. "This method is simple, cost-effective, and does not require complex tracking methods," says Riekeles.
The uniqueness of this approach lies in its simplicity: Instead of taking complex measuring equipment with us, an experiment of this kind could be conducted directly on a space probe or a Mars rover. Researchers would then be able to use a single photograph of the chamber system to determine whether potential microorganisms on an alien planet respond to chemical stimuli, without having to detect complex chemical traces. The method has the potential to significantly support space missions. "If we develop it further, it could be a valuable addition to existing techniques for detecting life on other planets," explains Riekeles. The next steps include miniaturizing the technology and testing under simulated space conditions.
Another advantage of this method is that it consumes little energy and requires minimal human intervention. This is especially important for space missions where resources are limited. If the method proves successful in further tests, it could be used in future Mars missions.
original publication
Frontiers | Application of chemotactic behavior for life detection
also read
Mystery solved: How ancient microbes can breathe without oxygen | Pugnalom
Microbes on seagrasses: GEOMAR study shows high antibiotic potential | Pugnalom
