Strange DNA 'borgs' discovered in California

Scientists accidentally discovered a mysterious — and unusually large — DNA structure deep in the mud in California wetlands. The structure, known as a "Borg," likely belongs to a single-celled organism and carries many genes that are unknown to science. It's not totally clear what these massive strings of DNA do, but they may help supercharge the organisms' ability to break down chemicals in the soil.

"I haven't been this excited about a discovery since CRISPR," senior author Jillian Banfield, geomicrobiologist at the University of California, Berkeley, wrote on Twitter. (CRISPR is the groundbreaking gene-editing technology that is based on a natural defense mechanism found in bacteria.) "Imagine a strange foreign entity, neither alive nor dead, that assimilates and shares important genes."

Banfield's son suggested naming the structures "Borgs" after the famous Star Trek aliens, who gather and assimilate the technology and knowledge of other alien species. The researchers published their findings, which haven't yet been peer-reviewed, to the preprint database bioRxiv. 

Related: Code of life: Photos of DNA structures

Banfield and her team discovered the Borgs while digging deep in California's wetlands for fragments of DNA that are involved in the carbon cycle, the process by which carbon is recycled through the environment, according to Nature. They then identified 19 different types from California and similar areas in Colorado.

The researchers don't yet know what these Borgs are, or what they do, but think the weird entities likely reside in single-celled organisms known as archaea. Their early study suggests that the newfound structures are a type of extrachromosomal element (ECEs) — DNA stored outside of an organism's chromosomes, which are tightly-packed structures that house the majority of an organism's genes. 

Microbes can share many different ECEs with each other to carry out useful functions that aren't necessarily "essential," such as antibiotic resistance, according to Nature. Commonly known ECEs are viruses or plasmids, which are tiny DNA molecules that can be found in bacteria (and some other cells), and typically give some kind of genetic advantage to bacteria such as antibiotic resistance.

Borgs are "gigantic in size," said lead author Basem Al-Shayeb, an NSF graduate research fellow at the University of California, Berkeley. The researchers found the DNA can have lengths of up to around 1 million base pairs — the nucleic acid duos that form the rungs of the DNA molecule. That length makes them about a third of the size of their host genomes, Al-Shayeb told Live Science in an email. 

"Their genes are quite different from what you would find on previously described ECEs," Al-Shayeb added. Borg DNA exists in a linear, rather than the traditional circular form found in viral and plasmid genomes, he said. What's more, they have unusually repetitive regions, which is not a common feature found in the genomes of viruses or plasmids. 

"I would say they are most exciting not because any single Borg feature is incredibly unique, but the combination of these features together makes the Borgs remarkable," Al-Shayeb said. Almost 80% of the Borgs genes have "completely unknown functions," he added. 

In the remaining 20% of the genome, they found that the borgs had acquired many genes that would "augment" their hosts' capabilities. For example, they think that the Borgs likely boost their host's metabolisms by increasing the host's ability to metabolize methane. 

Borgs are like "turbo boosters" for methane metabolism, Banfield wrote on Twitter. "This means they could have significant climate impacts." In the future, Borgs could potentially become a useful tool in capturing greenhouse gases from the environment, Al-Shayeb agreed. 

They found that the Borgs also had genes that may improve protein production, boost nitrogen fixation (or the process by which nitrogen in the air is converted into organic compounds that crops can use to survive and grow) and boost extracellular electron transfer (a process that's needed for organisms to respire compounds aside from oxygen). That's "also why we believe we found these deep underground in soils devoid of oxygen," Al-Shayeb said.

In all the places that they found Borgs, they also found DNA belonging to archaea known as Methanoperedens, according to Science Magazine. That suggests that the Borgs may exist inside these microbes, but the scientists don't know for sure because they can't grow Methanoperedens in the lab to test the idea. Whatever this structure is, it's "pretty exciting," W. Ford Doolittle, an emeritus professor in the Department of Biochemistry and Molecular Biology at Dalhousie University in Canada, who was not part of the study, told Science. 

Still, others aren't as convinced. Mart Krupovic, an archaeal virologist at the Pasteur Institute in Paris, who was not involved in the study, told Chemical & Engineering News that the Borgs might not be totally unique but rather a type of giant plasmid, also known as megaplasmid. 

Still, "there is so much that we currently don't know about the Borgs," Al-Shayeb said. "It will be a great adventure to learn more about them."

Originally published on Live Science.