Scientists at the Bose Institute, an autonomous institute of the Department of Science and Technology (DST), have studied archaea — a domain of ancient organisms — to find clues to survival strategies of microorganisms by adapting to harsh conditions with the help of their toxin-antitoxin (TA) systems.

Archaea, which means “ancient things” in Greek, are one of the oldest forms of life on Earth and belong to a group called the third domain of life.

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Many archaea live in some of the harshest environments on Earth, which makes them ideal for studying how life can survive in tough conditions.

The team, led by Dr Abhrajyoti Ghosh at the Department of Biological Sciences, explored how certain archaea toxin-antitoxin (TA) systems help these organisms cope with high temperatures.

In the study, published in the journal mBio, Ghosh and his team studied a specific TA system in a heat-loving archaeon called Sulfolobus acidocaldarius to understand how it helps these organisms.

They examined S. acidocaldarius, which lives in environments with hot volcanic pools like Barren Island in the Andaman and Nicobar Islands in India and some other volcanic areas in the world, that can get as hot as 90 degrees Celsius.

The detailed analysis of the VapBC4 TA system that helps survival in the high-temperature environment, shows its important role during heat stress. They found that the VapC4 toxin carries out several functions, such as stopping protein production, helping the organism form resilient cells, and influencing biofilm creation. When the cell faces heat stress, a stress-activated protease (which hasn’t been identified in archaea yet) may break down the VapB4 protein (which otherwise checks the VapC4 toxin’s activity).

Once VapB4 is gone, the VapC4 toxin is released and can stop protein production. This block in protein production is part of a survival strategy that helps cells form “persister cells” during stress. These persister cells go into a resting state, conserving energy and avoiding making damaged proteins. This dormancy helps them survive tough conditions until the environment improves, the scientists said.