David's theory of evolution: Shapiro's view in action (Evolution)

by David Turell @, Wednesday, January 22, 2020, 19:53 (246 days ago) @ David Turell

Bacteria have the CRISPR-cas mechanism to fight phage viruses:


"CRISPR-Cas is an immune system that protects bacteria against infection by viruses (called phages).

"The system works by stealing a small piece of viral DNA and using this to target and destroy matching sections of virus genome during a future infection.

"Targeting by CRISPR-Cas breaks down the virus genome, meaning that new copies of the virus cannot be made.

"Previously, the Westra and van Houte groups of the Environment and Sustainability Institute on the University's Penryn Campus in Cornwall showed that CRISPR-Cas can provide excellent protection against "lytic" phages, that is phages that multiply inside the host cell and cause the bacterial cell to burst releasing more viral particles.


"This type of autoimmunity was caused by the CRISPR-Cas system targeting viral DNA that had been incorporated into the host's own genome, leading to host cell death and virus release.
They found that bacterial cells that had lost the CRISPR-Cas system from their genome avoided the damage caused by autoimmune targeting, survived and proliferated.

"'Here, the absence of this key immune system was an advantage," explain the authors.

"They also highlight that "anti-CRISPR proteins, which are small inhibitors produced by the phage to counteract the host CRISPR-Cas immune response and had previously been thought to only benefit the phage that makes them, also provide protection for the host. In this scenario, disabling the host immune system blocks autoimmunity and prevents bacterial death.'"

Comment: We use the CRISPR system to edit DNA experimentally. But this is not a design system for new species. Bacteria must be able to protect themselves.

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