CRISPR: Bacteria’s Adaptive Defense Mechanism

The idea that single-celled bacteria can defend themselves against viruses in ways similar to the human immune system has long fascinated scientists. About twenty years ago, researchers discovered an adaptive defense system known as CRISPR, which enables bacteria to recognize and destroy viruses upon repeated encounters. A recent study has deepened our understanding of how bacteria use this system to “vaccinate” themselves against bacteriophages.

The CRISPR System and Its Mechanism

The CRISPR system relies on the ability of bacteria to modify their genetic code. After exposure to a virus, bacteria can use a special enzyme to create openings in their genome, where they can insert small pieces of viral DNA, known as spacers, which help them recognize and combat the virus in the future.

Scientists have used this enzyme as a tool for cutting and editing DNA in laboratory experiments and gene therapies. However, much was still unknown about how this process is executed in bacteria.

Laboratory Experiments and Recent Discoveries

To understand how bacteria capture the DNA of invading viruses, researchers conducted laboratory experiments using Streptococcus pyogenes bacteria and the viruses that infect them. During the infection phase, most viruses immediately destroy the cell in a process known as lysis. However, sometimes viruses hide within the bacterial DNA and become dormant, a situation that is difficult to study.

The research team infected some bacteria with viruses that can become dormant and others with genetically modified viruses that remain active. They then collected the surviving cells and examined their genetic code to see if they had added new spacers derived from the viral DNA.

Significance of the Results and Future Applications

The researchers found that bacteria added more spacers from viruses that could become dormant. During these periods, bacteria can capture small pieces of viral DNA and store them in their genome.

These findings are “remarkable,” offering new insights into the interactions between viruses and bacteria. They could contribute to improving viral therapies, where scientists use viruses to treat infections caused by antibiotic-resistant bacteria.

Conclusion

The CRISPR system represents a revolutionary step in our understanding of how bacteria defend themselves against viruses. By studying the mechanisms bacteria use to store and recall viral DNA, new strategies can be developed to combat bacterial resistance to antibiotics and to create new virus-based treatments.