A study involving UC Berkeley researchers has discovered unique DNA sequences with the potential to encourage cellular methane consumption, which could combat the greenhouse gas’s harmful effect on climate.
The preprint study, authored by UC Berkeley biogeochemist Jillian Banfield and researchers from the Innovative Genomics Institute, named the genetic elements “Borgs” after the “Star Trek” alien characters that “assimilate” the genes of other alien beings, according to researcher and the study’s first author Basem Al-Shayeb.
Similar to these aliens, the DNA can obtain varying functionalities from an organism, mainly methane-oxidizing archaea, or cell and other chromosomal elements, according to the study.
“We found this extrachromosomal element … that looked very strange to us because it didn’t look like a virus or a plasmid or a minichromosome,” Al-Shayeb said.
Rather, the Borg was “humongous” and linear as opposed to the conventional circular form of a plasmid — another type of DNA that replicates outside of a host’s chromosomes. Inverted terminal repeats — elements necessary for genome replication and integration — line both ends of the genome, which Al-Shayeb noted is unusual.
The microbes Borgs are observed in were found in samples of wetland soil, sediment and groundwater devoid of oxygen, Al-Shayeb said. Instead, the microbes exhibit extracellular electron transfer, or the ability to exchange electrons with other compounds, boosting cell respiration and the ability to generate electricity.
Borgs also provide responses to changing environmental stresses on the cell, potentially allowing the host to survive with limited resources, the study states.
“By this process, Borgs could play a previously unrecognized role in controlling greenhouse gas emissions,” the study reads.
These traits distinguish Borgs from any other known extrachromosomal archaeal elements, indicating a “distinct evolutionary origin,” according to the study. Al-Shayeb noted that archaea are a generally understudied organism group.
About 80% of the genome consists of genes that are unknown to science, as they code for uncharacterized proteins, according to Al-Shayeb. The other 20% include genes that code for methane oxidation and nitrogen fixation, the process by which microbes extract nitrogen from the environment and convert it into beneficial compounds.
“We still don’t know what it is that they do or what their purpose is,” Al-Shayeb said. “That’s a whole other venture to go and figure out what those functions are.”
Currently, 19 kinds of Borgs have been identified; each shares core genes and differs in capabilities such as nitrogen fixation. The genetic elements can also exchange genes between one another, according to Al-Shayeb.
The study’s findings are a starting point for pursuing an understanding of how Borgs could remove methane from the environment.
“If that is something that we’re able to do, then that would be very significant in the fight against climate change,” Al-Shayeb said.
