Researchers Probe Secrets of Bacterial Immune System

Saturday, October 22, 2016 - 13:07

Researchers of New Zealand's University of Otago and the Netherlands are investigating the secrets of a surprisingly flexible bacterial immune system, called CRISPR-Cas.

According to Phys.org, CRISPR-Cas system is a prokaryotic immune system that confers resistance to foreign genetic elements such as those present within plasmids and phages, and provides a form of acquired immunity.

Bacteria are constantly under attack by viruses that try to infect them by injecting viral DNA just like humans. This foreign DNA (together with other invading DNA, such as plasmids) has a major impact on the evolution of microorganisms. CRISPR-Cas systems can remember and destroy invading DNA by storing short, invader-derived, pieces of DNA (called 'spacers') into their genetic memory banks.

Based on the earlier research, the team discovered that viruses and plasmids, which can avoid recognition by mutating their DNA, will trigger the bacteria's CRISPR-Cas system to respond by quickly acquiring new immunological memories from these mutated threats.

Associate Professor Fineran explains; "We infected the bacteria with plasmids not previously encountered, or with mutated plasmids triggering the primed adaptation response. By making use of the advances in next generation sequencing through New Zealand Genomics Ltd, we analyzed more than 20 million newly acquired spacers."

The team discovered that the acquisition of memories from plasmids not previously encountered was very inefficient in comparison to the mutated plasmids. By studying the order in which these new memories were acquired, the researchers developed a new model for primed adaptation.

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