Scientists have discovered a mechanism used by microbes that live in salty lakes in Antarctica to aid growth and survival. Researchers from the University of New South Wales sampled water in remote regions of Antarctica over 18 months, even during winter. Their work revealed a strain of salt-loving microbes that carried a plasmid, a small bit of DNA that can independently replicate inside of a host cell. Often plasmids carry genes that are advantageous to an organism.
The plasmids found in the Antarctic microbes were a little different than plasmids that are familiar to us. "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; but the plasmids that we found in the Antarctic microbes were masquerading as viruses,” explained the research team leader, UNSW scientist Professor Rick Cavicchioli.
These plasmids not only replicated, but they also migrated from their hosts. “They produced proteins which went into the host's membrane, which then allowed the membrane to bud off containing the plasmid DNA,” continued Cavicchioli. “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.”
This work has been published in the journal Nature Microbiology. “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," noted the first author of the report, Dr. Susanne Erdmann.
The microbe described in this work is a type of haloarchaea, which are known to swap genetic material with each other often. The living is easy for these bacteria in Deep Lake, which remains liquid at a cool minus 20 because of its high salt content. Formed around 3500 years ago when the continent of Antarctica rose and trapped a portion of the ocean. Rare samples collected from the Rauer Islands, about 35 kilometers away from the lake, contained the haloarchaea microbes.
"We also discovered that the plasmids could take some of the DNA from the host microbe, integrate it into their own DNA, produce membrane vesicles around themselves, and then go off and infect other cells," said Professor Cavicchioli. "The findings are therefore relevant to Antarctic science as well as biology as a whole."
Learn more about research performed by this team on the salt-loving microbes of Antarctica from the video.