Cold-loving bacteria offer clues to life on Mars

A bacteria discovered in the Canadian high Arctic thrives at the coldest temperature known for bacterial growth, as cold as that of the surface of Mars.

Scientists led by McGill University discovered the microbe that is able to thrive at -15 degree Celsius in the permafrost on Ellesmere Island.

The bacterium offers clues about some of the necessary preconditions for microbial life on both the Saturn moon Enceladus and Mars, where similar briny subzero conditions are thought to exist.

Researchers, led by Professor Lyle Whyte and fellow Nadia Mykytczuk discovered Planococcus halocryophilus OR1 after screening about 200 separate High Arctic microbes looking for the microorganism best adapted to the harsh conditions of the Arctic permafrost.

"We believe that this bacterium lives in very thin veins of very salty water found within the frozen permafrost on Ellesmere Island," said Whyte.

"The salt in the permafrost brine veins keeps the water from freezing at the ambient permafrost temperature, creating a habitable but very harsh environment. It's not the easiest place to survive but this organism is capable of remaining active (breathing) to at least -25ºC in permafrost," said Whyte.

In order to understand what it takes to be able to do so, researchers studied the genomic sequence and other molecular traits of P halocryophilus OR1. They found that the bacterium adapts to the extremely cold, salty conditions in which it is found thanks to significant modifications in its cell structure and function and increased amounts of cold-adapted proteins.

These include changes to the membranes that envelop the bacterium and protect it from the hostile environment in which it lives.

The genome sequence also revealed that this permafrost microbe is unusual in other ways. It appears to maintain high levels of compounds inside the bacterial cell that act as a sort of molecular antifreeze, keeping the microbe from freezing solid, while at the same time protecting the cell from the very salty exterior environment.

"I'm kind of proud of this bug. It comes from the Canadian High Arctic and is our cold temperature champion, but what we can learn from this microbe may tell us a lot about how similar microbial life may exist elsewhere in the solar system," Whyte said.