Strange libraries of supplementary genes nicknamed “Borg” DNA appear to supercharge the microbes that possess them, giving them an uncanny ability to metabolize materials in their environment faster than their competitors.
By learning more about the way organisms use these unusual extrachromosomal packets of information, researchers are hoping to find new ways of engineering life to take a big bite out of methane emissions.
In the wake of a study publicized last year (and now published in Nature), researchers have continued to analyze the diversity of sequences methane-munching microbes store in these unusual genetic depositaries in an effort to learn more about the evolution of life.
Named after the Star Trek aliens that assimilate other beings into a collective hive mind, these mysterious DNA elements perform a similar trick by absorbing beneficial genes from many different organisms over vast periods of time.
These genetic Borgs were discovered in a methane-consuming microbe called Methanoperedens, and it appears they’ve been able to optimize themselves over the millennia to amplify the organism’s ability to soak up methane.
“Imagine a single cell that has the ability to consume methane,” says environmental scientist Kenneth Williams, from the Lawrence Berkeley National Laboratory in California. “Now you add genetic elements within that cell that can consume methane in parallel and also add genetic elements that give the cell higher capacity.”
“It basically creates a condition for methane consumption on steroids, if you will.”
Scientists think Borgs are a form of DNA known as an extrachromosomal element (ECE). These packets of genetic material exist outside the organism’s chromosomes, and are endowed with tools that allow gene assimilation to take place.
Unlike other ECEs, Borgs have a linear rather than a circular structure. They’re also much longer than normal. In samples taken from underground soil, aquifers and riverbeds, the team discovered 19 distinct Borg ECEs, including four complete sequences.
Through advanced genome analysis, it was revealed that Borgs match a lot of the methane-metabolizing genes in Methanoperedens itself. In fact some Borgs have all the mechanisms required to eat up methane on their own, provided they’re within a cell that is able to express the Borg’s genes.
The scientists hypothesize that Borgs might be leftover fragments of a wide range of microbes absorbed by Methanoperedens, although not every Methanoperedens microbe contains Borgs. One explanation for this is that Borgs act as stores for metabolic genes that are only needed at specific times – such as when there’s a lot of methane around.
That would mean some Methanoperedens microbes can go above and beyond their normal methane consumption ability, thanks to the presence of Borgs. There’s still a lot to unpack about these fascinating bits of DNA though.
“There is evidence that different types of Borgs sometimes coexist in the same host Methanopreredens cell,” says environmental scientist Jillian Banfield, from the University of California, Berkeley. “This opens the possibility that Borgs could be spreading genes across lineages.”
The researchers are now closely examining how Borgs can affect processes both biological (in the way cells develop) and geological (in the way additional methane is captured from the surrounding environment).
It’s a long, long way off – if we get there at all – but perhaps one day, Borg-packed microbes could be engineered to make a sizeable dent in annual emissions of methane, a gas that’s currently estimated to account for about 30 percent of human-driven global warming.
Field work is being undertaken in parallel with lab analysis to reveal more about how these extraordinary Borgs work, and to trace back a history that could potentially extend to billions of years.
“Assuming that these genes either augment Methanoperedens energy metabolism or extend the conditions under which they can function, Borgs may have far-reaching biogeochemical consequences, with important and unanticipated climate implications,” write the researchers in their published paper.
The research has been published in Nature.