Study uncovering multiple new, unusual bacterial immune defense mechanisms could pave the way toward new biotech tools

phys.org | 1/25/2018 | Staff
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Until a decade ago, scientists were not aware that bacteria had complex immune systems - ones that could keep up with the pace of evolution in viruses called phages that infect bacteria. That changed with the discovery of what is now the most famous bacterial immune mechanism: CRISPR. Scientists realized that CRISPR is a natural gene editor, and it has revolutionized the world of biological research in thousands of labs around the world. Researchers now understand that most microorganisms have sophisticated immune systems of which CRISPR is just one element; but there has been no good way to identify these systems.

In a massive, systematic study, Prof. Rotem Sorek and his team at the Weizmann Institute of Science have now revealed the existence of 10 previously unknown immune defense mechanisms in bacteria. "The systems we discovered are unlike anything we had seen before," says Sorek. "But among them, we think, are one or two that might have the potential to increase the gene-editing toolbox, and others that point to the origins of the human immune system." The results of their study were recently published in Science.

Bacteria - CRISPR - War - Phages - Sorek

Bacteria cannot rely on CRISPR alone in the war against phages, explains Sorek, a member of the Institute's Molecular Genetics Department. Indeed many phages have "anti-CRISPR" proteins that cancel CRISPR activity, suggesting that other systems take up the slack. Sorek and his team began their search for these systems by creating a computer program that would scan all the bacterial genomes that have ever been sequenced - around 50,000 genomes in all. Rather than look for sequences with predefined characteristics, the algorithms they created searched for the "statistical signatures" of genes involved in defense - for example, their location in "defense islands" where several defense-related genes are found near one another. Then, because immune system genes...
(Excerpt) Read more at: phys.org
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