Scientists have discovered bacteria capable of “sensing” the Earth’s magnetic field in deep sea vents.
Bacteria that can align with Earth’s magnetic field have been found in a new habitat. Previously spotted on land and in shallow waters, these magnetically attracted bacteria are now confirmed to thrive deep in hydrothermal vents. Despite the difficult conditions, the bacteria managed to adapt and survive in an environment that was not ideal for their typical needs.
Magnobacteria are of interest not only for the role they play in Earth’s ecosystem but also in the search for extraterrestrial life. Evidence of their existence can remain in rocks for billions of years. Their magnetic tendencies can also provide a record of how the magnetic poles shift over time. This new discovery brings hope to researchers that magnetobacteria can be found in unexpected locations, on and perhaps even on Earth Mars or further.
Magnetobacteria seem to have superpowers. Just like the character Magneto in Marvel Comics, they can “sense” the Earth’s magnetic field. These microorganisms contain magnetospheres, which are iron crystals encased in a membrane, which arrange themselves to align with Earth’s magnetic field and orient the bacteria like a compass.
This causes the bacteria to travel in the direction of the Earth’s magnetic field lines leading north or south, like trains on a magnetic track. As part of their life cycle, they play an important role in the biogeochemical cycle of carbon, nitrogen, phosphorus, and other major elements in nature. They have been well studied on land and in shallow water, but have rarely been studied in deeper waters where collection can be a challenge.
In September 2012, a team including researchers from the University of Tokyo set off on a scientific cruise to the Southern Mariana Basin in the western Pacific Ocean. Using a remotely operated underwater vehicle called Hyper DolphinThey collected a “chimney” from a hydrothermal vent field 2,787 meters (nearly 4.5 times the height of the Tokyo Skytree or more than 6 times the height of the Empire State Building in New York) underwater.
Hydrothermal vents form when sea water seeps down underground, eventually getting super hot – up to 400 degrees. Celsius – Through the magma that causes it to boil again. The erupting waters deposit minerals and metalloids in the ocean which then layer in to form stacks, providing a warm and rich habitat for many unique life forms.
“We discovered bacteria with magnetotaxis living in the chimney, which we did not expect. Because of the shape of the chimney, it lacked the clear vertical chemical gradient that these bacteria usually prefer,” explained Associate Professor Yohei Suzuki of the University of Tokyo Graduate School of Science. We have essentially collected bullet-shaped magnetic particles, which we see as a “primordial” shape and conclude that they haven’t changed much over thousands of years. In fact, the environment in which we find them is similar to that of early Earth about 3.5 billion years ago, when the ancestor of magnetobacteria appeared.
Bacteria were collected from the chimney edge using a magnet. The team then examined the genetic data and found that it was related to Nitrospinae bacteria, which are known to play an important role in carbon fixation in deep-sea environments, but were not known to contain any magnetic groups.
“Deep-sea hydrothermal vents are attracting attention not only as cradles of unique underwater life, but also as potential similar habitats for extraterrestrial life,” said Suzuki. “The environment in which we sampled the bacteria is similar to what we think Mars was like when there was still water flowing on its surface, about 3 billion years ago.”
Fossilized remains of magnetic particles in magnetobacteria (known as magnetofossils) can be preserved in rocks for billions of years. These magnetic fossils can help researchers piece together ancient geomagnetic history, and are good candidates in the search for extraterrestrial life.
And in 1996, the Martian meteorite Allan Hills 84001, about 3.6 billion years old, caused a worldwide sensation when it appeared to contain fossilized iron crystals from bacteria-like life. This claim has since been widely disputed, but Suzuki still has hope for future discoveries: “Magnetobacteria provide evidence for an early diversity of bacteria, and we hope they can be found outside Earth, perhaps on Mars or icy moons.” Currently, we will continue to look for more evidence of them in different types and ages of rocks on Earth where they were not previously thought to inhabit.
Reference: “Bullet-shaped magnetic particles and metagenome-based magnetic gene profiles in a deep-sea hydrothermal vent stack” By Shinsaku Nakano, Hitoshi Furutani, Shingo Kato, Mariko Kodoka, Toshitsugu Yamazaki, and Yohei Suzuki, June 27, 2023, Available here. Frontiers in Microbiology.
This research was supported by Project TAIGA, Grant Assistance for Scientific Research in Innovative Areas (#201090060 from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan, Grant Assistance for Scientific Research B (#19H0330100 from MEXT) and JSPS KAKENHI (grant numbers : 25287137 and 16K13896)