Engineering of CRISPR-BrCas12b System for Efficient Genome Editing in Thermophilic Bacteria
This study reports the development of a thermostable CRISPR-BrCas12b system capable of precise genome editing at 45–70°C in the thermophilic bacterium *Thermus antranikianii*, thereby overcoming previous tool limitations and enabling its use as a next-generation cell factory.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Deep within the world of microscopic life, there exists a realm where heat is not a barrier but a home. These are thermophiles, bacteria that thrive in scorching environments like hot springs and deep-sea vents, growing best at temperatures that would instantly kill most other life forms. For scientists, these heat-loving organisms are more than just biological curiosities; they are potential factories for the future. Because they live in such extreme heat, they produce enzymes that are incredibly stable and can work efficiently in industrial processes without needing expensive cooling systems. However, harnessing them for manufacturing has been difficult. To turn a microbe into a factory, scientists must be able to rewrite its genetic code, a process known as genome editing. For decades, the tools used to edit genes worked well at human body temperature but failed miserably in the heat required by these thermophiles, leaving a vast reservoir of biological potential untapped.
A team of researchers at Sun Yat-sen University has now bridged this gap by engineering a new tool specifically designed to work in the heat. They focused on a bacterium called Thermus antranikianii, a heat-loving microbe that grows rapidly and has a streamlined genetic structure, making it an ideal candidate for industrial use. The challenge was that the standard gene-editing tools, which rely on a molecular machine called Cas9, simply could not function at the 60 degrees Celsius temperatures where this bacterium thrives. To solve this, the scientists turned to a different molecular machine called BrCas12b. Unlike its more famous cousin, BrCas12b is naturally stable at high temperatures. The researchers took this protein and adapted it to work inside Thermus antranikianii, creating a system that can cut and edit DNA precisely within the bacterium's hot environment.
The core of their achievement lies in how this new system operates. The researchers built a compact genetic tool that acts like a pair of molecular scissors. This tool consists of the BrCas12b protein, which does the cutting, and a guide RNA, which acts as a GPS to lead the scissors to the exact spot in the DNA that needs editing. The team tested this system across a range of temperatures and found that it works with high precision between 45 and 70 degrees Celsius, perfectly matching the growth conditions of the bacterium. They discovered that the system is most efficient at 65 degrees Celsius. Furthermore, they mapped out where this tool can cut. It looks for a specific three-letter code in the DNA sequence to know where to start, and they found that it recognizes a TTN pattern, with a strong preference for TTT and TTC sequences. This allows the system to access a wide array of editable sites throughout the bacterium's entire genome, offering scientists a vast array of options for genetic modification.
To prove the system worked, the researchers first tested its ability to turn genes off. They introduced the tool into the bacteria along with a gene that produces the enzyme β-galactosidase. When the editing tool was switched on, it successfully cut the gene, and the bacteria showed a significant drop in the enzyme's activity, indicating that the system could effectively inactivate specific genes, a crucial step for understanding how the bacteria work. Next, they tested the tool's ability to insert new genetic material. They aimed to insert a new piece of DNA into a specific location in the bacterial genome. The system successfully made a cut at the target site, and the bacterium's own repair mechanisms stitched in the new DNA exactly where intended. This confirmed that the tool could not only break genes but also add new instructions to the genome, a capability essential for building complex biological circuits.
The significance of this work extends beyond a single bacterium. The researchers showed that their tool is versatile and could likely be used in other heat-loving bacteria as well, provided they grow within the same temperature range. By providing a reliable way to edit the genes of Thermus antranikianii, they have removed a major bottleneck that has held back the use of this organism in research and industry. This new capability opens the door to engineering these microbes to produce valuable thermostable enzymes or to function as robust cell factories that operate efficiently in hot conditions. The development of this thermostable editing platform represents a practical step forward in synthetic biology, turning a difficult-to-manipulate microbe into a manageable and powerful tool for green manufacturing.
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