Antarctic salt-loving microbes provide insights into evolution of viruses

UNSW Sydney scientists studying microbes from some of the saltiest lakes in Antarctica have discovered a new way that the tiny organisms can share DNA that could help them grow and survive.

The research, based on 18 months of water sampling in remote Antarctic locations, including during the extreme cold of winter, could throw light on the evolutionary history of viruses.

The team unexpectedly discovered one strain of the Antarctic salt-loving microbes contained plasmids – small molecules of DNA which can replicate independently in a host cell, and which often contain genes useful to an organism.

“Unlike viruses, which encase themselves in a protective protein coat, plasmids usually move around by cell to cell contact, or as a piece of naked DNA,” says research team leader UNSW scientist Professor Rick Cavicchioli.

“But the plasmids that we found in the Antarctic microbes were masquerading as viruses. They produced proteins which went into the host’s membrane, which then allowed the membrane to bud off containing the plasmid DNA.

“The budded membranes, called membrane vesicles, allowed the plasmids to infect microbes of the same species that did not have any plasmids present, and then replicate themselves in the new host,” he says.

Study first author Dr Susanne Erdmann says: “This is the first time this mechanism has been documented. And it could be an evolutionary forerunner to some of the more structured protective coats that viruses have developed to help them spread and become successful invaders.

“This finding suggests some viruses may have evolved from plasmids,” she says. Source: Antarctic salt-loving microbes provide insights into evolution of viruses

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