Perplexing ‘Borg DNA’: Can they assimilate genes from other organisms?

A geo-microbiologist in the US has found DNA strands in her backyard that were too long to be of a virus and that had indications of containing DNA from other organisms

July 24, 2021 by Newsclick

A recent accidental discovery in the realm of DNA has stunned scientists who are yet to uncover all its implications. The discovery was of mysterious strands of DNA, which, researchers say, may assimilate genes from many other organisms found in their surrounding environment. If the assimilation turns out to be really happening, then it may lead to a fascinating phenomenon hitherto unknown, but for that, we will have to wait.

Jill Banfield, a geo-microbiologist at the University of California, Berkeley, found the mysterious DNA in her backyard. Banfield was not looking for these DNA strands in her backyard. Instead, she and her graduate student were looking for viruses that can infect archaea, which is a type of microbe mostly found in places devoid of oxygen, reported the Science magazine. They dug a meter or more below the surface and collected mud from there to search for archaea and their viruses. They then found the sequences of every bit of DNA found in the mud and put them through sophisticated computer program to scan sequences that signify a virus. But they landed up finding the mysterious DNA strands, too long to be of a virus and having indications of containing DNA from other organisms.

They have named these DNA strands as ‘Borg DNA’, – from the TV series ‘Star Trek’ where Borgs are cybernetic aliens that assimilate humans and other organisms as the means to achieve perfection. They have published the discovery in the pre-print server bioRXiv.

Banfield, reacting on the discoveries, tweeted—“I haven’t been this excited about a discovery since CRISPR. We found something enigmatic that, like CRISPR, is associated with microbial genomes.”

Banfield and her student found a DNA consisting of a million base pairs, which is huge. The base pairs are the fundamental units of the DNA (and RNA), they are the building blocks of DNA double helix and contribute to the typical structure of both the DNA and RNA.

A closer look at the DNA revealed more interesting facts and more peculiarities. More than half of the genes on the DNA strand (genes are the portions of a DNA or RNA that acts as codes for the making of a protein) were new. It had mirrored sequences at the end and showed having structures with the ability of self-replicating. DNAs replicate via a complex mechanism through which a single DNA becomes two and so forth.

In total, the researchers could isolate 23 DNAs that they think are the Borgs with 19 containing all the characteristics of the first Borg they discovered. After they found their first Borg sequence, they scanned microbial DNA available in public databases to find whether they can find anything similar. They found some in groundwater from Colorado and other versions in DNA from the discharge of an abandoned mercury mine in California and from a shallow riverbed in Colorado.

It is still unclear what the Borg DNA s exactly are. But certainly, they belong to a class called the Extrachromosomal Elements (ECE). The ECEs are found outside of a chromosome. It is the chromosome where most of the DNAs of an organism are found. In fact, long strands of DNAs get wrapped over the chromosome to be in a compact shape.

The ECEs are huge and can self-replicate with their presence both in and outside of the cell nuclei (the nuclei of a cell is where the DNAs are found wrapped and compacted in the chromosome).

“We can neither prove that they are archaeal viruses or plasmids or mini-chromosomes, nor can we prove that they are not,” the researchers wrote in the paper published in bioRXiv.

Banfield found that the Borgs are larger than other ECEs. The sequences of the Borgs also revealed another interesting feature. They found that the Borgs have similar features with Methanoperedens, a class of archaea that can oxidise methane. This suggests that the Borgs can be involved in the process methane oxidisation.

This is important and is of much interest for researchers like Banfield, because the process can reduce the amount of methane in the atmosphere, which is a greenhouse gas. It will be important to learn how microbes can oxidise methane.

However, there is a setback. Methanoperedens cannot be grown in a laboratory as of now. The other factor associated with it is that environmental DNA can be contaminated by other genetic material present in the same environment.

The Borg DNAs are indeed interesting findings, however, we do not know much about them as yet.

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