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Plasmids, Chromids, ICEs, Integrons...... Borgs!!
- Vyshakh Rajachandran
- Jul 24, 2021
- 2 min read
Ever imagined of discovering ‘Borgs’ one day on Earth? Well, then you all fantasy geeks will not be too disappointed. Yes, a group of scientists from University of California, Berkeley, CA, USA have discovered mysterious DNA structures that seem to scavenge and ‘assimilate’ genes from microorganisms in the environment; assimilating information (here genes) and technology of other organisms, much like the ‘Borgs’ from Star Trek. (The study was deposited in BioRxiv on 10th July 2021 and is not peer-reviewed yet.)
These unusual DNA structures, named Borgs are found to range in sizes from 600,000 bases to sometimes even 1 million bases, form a novel class of ‘Extrachromosomal Elements’ (ECEs). These unusual structures were discovered in an archaeon belonging to the Methanoperedens genus- a genus known to digest and destroy methane. In recent years, the field of ECEs have seen a number of interesting discoveries and although, the discovery of ‘Borgs’ are undoubtedly fascinating, still faces numerous questions about the uniqueness of these structures, especially with respect to their similarities with other large ECEs. Dr. Banfield, the corresponding author of the study asserts the uniqueness of these structures by citing: a) the enormous size of these structures, which are incomparable to other ECEs, b) they are linear unlike other ECEs which are circular in structure, c) presence of repetitive elements at each end of the strands and also have repetitive regions both within and between the presumptive genes.
Housing such an enormous structure (almost half the chromosome size) would be an energetically costly process and therefore, their maintenance inside the cells must be associated with some benefits. A comprehensive gene level comparison of Borg genes led to the understanding that these structures harbor genes for an entire metabolic process, say for in this instance; methane digestion. To strengthen the fact that ‘Borgs’ are indeed unique, Dr. Banfield added. ‘The size, combination and gene load are what make them different’. She also speculates that these novel class of DNA structures were once entire microbes, and Methanoperedens assimilated them much like the same way energy-generating mitochondria were gained from free-living bacteria by eukaryotes.
The invention of CRISPR and its associated proteins as a gene editing tool was a great boon for biotechnology. Interestingly, the still unexplored dark area of ‘Borg’ is expected to offer game-changing solutions in future. Dr. Banfield, being a pioneer in the area of how microbes influence the carbon cycle, particularly with reference to methane degradation is really optimistic that the untapped potential of ‘Borgs’ to degrade methane can have limitless possibilities in climate research and global warming!
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