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Wednesday, 28 September 2016

Like Immune Cells Bacteria can Memorize the Virus to Snap them down in Future

Bacteria like humans rely on an immune system to save themselves from the attack of viruses. As we read about immunogenic memory in immune cells, similarly bacteria can remember the virus they encounter and much easily snap them down in future. CRISPR which was discovered in mid 2000s, the researcher observed something peculiar within where it records conformation of viruses sequentially placing the most threatening virus memory in first in the order.

The research was published recently in the journal Molecular Cell by the researchers from Rockefeller University.

"Until now, no one knew if this organizational feature serves a purpose, let alone what that might be," says senior author Luciano Marraffini, who is an associate professor and head of the Laboratory of Bacteriology. "We found an answer: It allows the microbe to mount the strongest immune response against its most recent threat, which is likely to be the most potent one around." (as quoted from Phys dot org)

Microbial CRISPR captures the genetic snippets from the threat and mount them in a series like beads in a string. CRISPR associated with the enzyme Cas used these snippets to recognize and cut the virus. Thanks to the same editing tool which is now used often in molecular laboratory.

Marraffini and his graduate student Jon McGinn (co-author) in the lab together determined that a small section of bacterial genome called leader anchoring sequence is responsible to arrange the most recent viral snippet to the first position in CRISPR. When or if the sequence gets altered CRISPR actually stops the addition of new spacers and instead add them further downstream.

So when the researchers misplaced the spacer in an experiment they found that bacteria are getting vulnerable to the virus and still can defend them at lower concentration.

"An individual bacterium acquires a new spacer right when other infected cells in its surroundings are dying and releasing astronomical levels of new viral particles," McGinn says. "We think this system ensures the cell can protect itself when the colony it lives in is inundated by phage."

Source: Phys dot Org


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