Deepsea magnetic bacteria offer clues to 3.5 billion-year-old Mars

'Magnetotactic bacteria' were found thriving in a hydrothermal vent field six times the height of the Empire State Building.
Sade Agard
A remotely operated underwater vehicle named HYPER-DOLPHIN collects a “chimney” from a hydrothermal vent field.
A remotely operated underwater vehicle named HYPER-DOLPHIN collects a “chimney” from a hydrothermal vent field.

2012, Yohey Suzuki 

Researchers have made an exciting discovery regarding magnetotactic bacteria— a unique type capable of aligning themselves with the Earth's magnetic field.

Until now, these bacteria have only been observed in terrestrial and shallow water environments. However, an analysis of a hydrothermal vent has revealed that they can also thrive in the ocean's depths.

Magnetotactic bacteria's significance stretches far beyond their role in Earth's ecosystem. In fact, researchers passionately argue that these magnetic marvels could exist as far as Mars or other celestial bodies.

What's the significance of magnetosomes in bacteria?

Within their minuscule structures, magnetotactic bacteria harbor magnetosomes—iron crystals enveloped by a protective membrane. Astonishingly, these magnetosomes align themselves so that the bacteria become like living compasses, pointing in the same direction as Earth's magnetic field (towards the north or south).

Deepsea magnetic bacteria offer clues to 3.5 billion-year-old Mars
Like a compass, the iron-containing magnetosomes in the bacteria align towards the Earth’s magnetic poles, compelling them to move in a north or south direction depending on which hemisphere they inhabit.

Additionally, these bacteria play a crucial role in the natural cycling of vital elements like carbon, nitrogen, and phosphorous.

While extensively studied on land and in shallow water, investigating their behavior in deep water poses challenges in collecting them — until now.

In September 2012, a team of researchers, including scientists from the University of Tokyo, embarked on a scientific ocean cruise to explore the southern Mariana Trough in the western Pacific Ocean.

Equipped with a remotely operated underwater vehicle called HYPER-DOLPHIN, the researchers successfully retrieved a remarkable "chimney" from a hydrothermal vent field submerged at 2,787 meters. To put it into perspective, this depth is nearly 4.5 times the height of Tokyo Skytree or over six times that of the Empire State Building in New York.

"We discovered magnetotactic bacteria living on the chimney, which we didn't expect. Due to the chimney's shape, it lacks a clear, vertical chemical gradient which these bacteria typically prefer," the study's co-leader, Associate Professor Yohey Suzuki from the Graduate School of Science at the University of Tokyo, said in a statement.

Inspiring the search for extraterrestrial life

"The bacteria we collected contained mainly 'bullet’-shaped magnetosomes, which we see as a 'primitive' form and so inferred that they have not changed much over many millennia," he added.

"Indeed, the environment we found them in is similar to early Earth about 3.5 billion years ago, when the ancestor of magnetotactic bacteria is estimated to have emerged."

Using a magnet, the researchers collected bacteria from the rim of the chimney. Analyzing the genetic data, they made a surprising discovery: the bacteria were found to be closely related to Nitrospinae bacteria. Nitrospinae are recognized for their significant role in carbon fixation within deep-sea environments. Still, it was previously unknown that they belonged to any magnetotactic groups.

"Deep-sea hydrothermal vents attract attention not only as the birthplace of unique underwater life but also as a potential analogous habitat for extraterrestrial life," said Suzuki.

"The environment where we sampled the bacteria is similar to what we think Mars was like when there was still flowing water on its surface, about 3 billion years ago."

The complete study was published in Frontiers in Microbiology on June 27.

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