How an Arctic bacterium survives cold stress
doi:10.1038/nindia.2020.149 Published online 28 September 2020
A particular bacterium thrives in the frigid conditions of the Arctic Circle by adjusting the fatty acid composition of its cell membrane to temperature variations, researchers from the Indian Institute of Technology in Patna have discovered1.
This helps the bacterium keep its cell membranes in a fluid phase during freeze-thaw cycles — a finding that has potential applications in low-temperature biotechnological processes such as food production, waste processing, agriculture and medicine, the researchers say.
The scientists, led by Snehasis Daschakraborty, simulated cell membranes of Leeuwenhoekiella aequorea, a bacterium found in the Arctic Circle. They exposed these membranes, composed of various saturated or unsaturated lipids, to extremely low and below-freezing temperatures.
They found that below 7 degrees Celsius, the bacterial cell membrane transitions from a fluid-like phase to a gel phase. Near the transition temperature, they observed a separation between the fluid-like phase (formed by the unsaturated lipids), and the gel-like phase (formed by the saturated lipids).
Since such phase separation is fatal for the cell, the bacterium modifies the lipid composition of its membrane in such a way that the membrane remains fluid and functional even well below the freezing temperature.
The bacterium also uses a sensor protein to sense and adapt to such harsh environments. Such bacteria may provide clues to the search for alien life in extreme environments such as the polar caps of Mars, and the icy moons of Jupiter and Saturn, Daschakraborty says.
1. Erimban, S. et al. Cryostabilization of the cell membrane of a psychrotolerant bacteria via homeoviscous adaptation. J. Phys. Chem. Lett. 11, 7709-7716 (2020)