Scientists have found an entirely new class of magnetically sensitive bacteria that live nearly two miles beneath the surface of the Pacific Ocean, a discovery that could shed light on the emergence of life on Earth, and the potential existence of aliens on other worlds, reports a new study.
The unexpected detection of the strange organisms exposes the versatility of “magnetotactic” bacteria, a group of microbes that contain magnetic crystals in their cells that keep them aligned with Earth’s magnetic field lines. While many animals have evolved receptors that are attuned to our planet’s magnetism, these bacteria differ in that they have literal magnets inside them that move with magnetic lines whether the microbes are living or dead.
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Magnetotactic bacteria have captivated researchers since they were first identified in the 1960s for a host of reasons, including the crucial role they play in the cycle of bioessential nutrients, such as carbon, nitrogen, and phosphorus.
Their sturdy interior crystals can also be preserved in the geological record, where they are a source of insights about both microbial ecosystems and magnetic activity in the deep past. Given that these “magnetofossils” could theoretically survive for billions of years, scientists involved in the search for extraterrestrial life have suggested searching for the remains of alien magnetotactic microbes on other worlds, such as Mars.
Many species of magnetotactic bacteria have been found living in habitats on land and shallow water, and humans even conducted experiments on them in space. Now, a team of researchers reports the first discovery of magnetotactic bacteria living on the “chimney” of a hot hydrothermal vent system in the Mariana Trough, a deep-sea environment that may be similar to the habitats where life first arose on Earth, according to a study published in Frontiers of Microbiology on Tuesday.
“We were very surprised to find them,” said Yohey Suzuki, an associate professor in Earth and planetary sciences at the University of Tokyo and a senior author of the study, in an email to Motherboard. He noted that magnetotactic microbes usually prefer environments with vertical chemical gradients, which the vent chimneys lack.
Suzuki and his colleagues came across the weird bacteria during a 2012 deep-sea expedition with the remotely operated vehicle HYPER-DOLPHIN. The robotic vehicle descended to a depth of nearly 2,800 meters to study hydrothermal vents in the Mariana Trough, an 800-mile-long basin located in the western Pacific Ocean near Guam. The magnetotactic bacteria collected by the team are related to Nitrospinae, an abundant group of marine bacteria that play key roles in the global carbon and nitrogen cycles.
Hydrothermal vents are produced by magma-heated seawater that deposits and sculpts otherworldly structures on the seafloor, where temperatures can reach more than 700° Fahrenheit. Despite these seemingly inhospitable conditions, vents are often teeming with lifeforms that have learned to thrive off the abundant chemical energy emitted by these underwater hotspots, which are usually beyond the reach of sunlight.
Hydrothermal vents formed many billions of years ago in Earth’s ancient oceans, and they may exist in the subsurface oceans of other worlds, such as Jupiter’s moon Europa or Saturn’s moon Enceladus. For this reason, scientists think that these habitats may have been the cradle of life on Earth, as well as a promising place to look for life on alien planets.
Indeed, a scientific controversy has already erupted over the reported detection of magnetic remnants of life in the Martian meteorite Allan Hills 84001, which was discovered in 1984, though scientists have since concluded that the mysterious features in the space rock were likely made by geological processes that did involve alien life.
“As previously reported from Martian meteorite Allan Hills 84001, fossils of magnetotactic bacteria are thought to be preserved for a long time as biosignatures,” Suzuki said. “Non-specific habitation of magnetotactic bacteria means that such easily detected biosignatures can be found anywhere hydrothermal activities occurred in deep-sea environments (Mars and icy moons).”
“As for Earth, the ancestor of magnetotactic bacteria emerged 3.5 billion years ago, before the divergence of major bacterial phyla and very close to the first emergence of life,” he added. “The theory of the first emergence of life needs minerals for cellular materials and metabolites. Magnet is made up of a mineral called magnetite, which might be used by the first life.”
In other words, these bacteria can help scientists trace the origin of life back to the Precambrian era, which is the vast time period before complex animals and plants emerged about 550 million years ago. Suzuki and his colleagues plan to continue looking for more species of magnetotactic bacteria that might help answer the question of how life arose on our planet, and whether it exists elsewhere in the universe.
“We are searching for magnetotactic bacteria from more usual places such as the deep subsurface and volcanic rocks,” Suzuki said. These future studies could yield insights about “the meaning (function) of the magnet synthesis other than magnetic navigation and if the magnetic fossils are found in Precambrian rocks on Earth,” he concluded.
