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Viruses swipe bacterial immune system

The CRISPR narrative (pronounced “crisper”) recently took a twist, with a team of Boston area scientists reporting that a virus has a CRISPR system of its own to inactivate a separate host viral defense canada goose replica system.

Normally, CRISPR acts as a rudimentary immune system for bacteria buy canada goose jacket cheap against the onslaught of bacteria targeting viruses, called phages. Bacteria that defend themselves with CRISPR have a series Canada Goose online of short “spacer” sequences in their genome, flanked by repeats of the CRISPR sequence. These canada goose outlet store locations spacers contain pieces of the genomes of past invaders in the canada goose bacterial species’s history. The bacterium transcribes these sequences into RNA, which are processed canada goose black friday sale into smaller crRNAs, with each molecule targeting the sequence Canada Goose Coats On Sale from a unique type canada goose clearance of invader. If infiltrated by one such invader, the bacterium’s crRNA targets the phage’s Canada Goose Online genome 2018 canada goose outlet for degradation.

It must have come as a surprise when Seed et al. (2013) found CRISPR sequences not in canada goose coats a bacterial genome, but in phage genomes. It turns out that the interplay between phages and the bacterium that causes cholera, Vibrio cholerae, plays a role in the severity of the infection in humans. When V. cholerae is hit with persistent attacks by phages, it is a less Canada Goose Outlet effective human pathogen. The researchers discovered that one of the tools up phages’ sleeves is using CRISPR to inactive a V. cholerae anti phage defense system. More The host defense is unrelated to CRISPR, an innate immunity defense rather than CRISPR’s adaptive defense (adaptive since DNA from new pathogens is stored in the bacterium’s genome as additional spacers, giving protection against future infections). This is the first time such canada goose deals an interaction has been described.

The implications cheap Canada Goose are far reaching, in both practical terms and basic science. For one, we face a startling antibiotics problem as mainstay treatments lose their effectiveness. Phage treatments might allow for targeted killing of the offending pathogens, canada goose outlet toronto factory while sparing the “good bacteria” that keep us healthy. Understanding phage bacterium interactions in disease relevant microbes like V. cholerae will canada goose coats on sale be necessary for developing these sorts of treatments. A phage designer might, for instance, mistake the viral canada goose clearance sale CRISPR system as junk cargo picked up through horizontal gene transfer. But we now know that, at least in this circumstance, the CRISPR system is necessary for the phage to infect its host. It also gives us another tool to fight back against bacteria, since we have a good understanding of how to engineer CRISPR.

From a basic science standpoint, it is becoming very clear that the sorts of evolutionary arms races long canadian goose jacket seen in the animal kingdom (the gazelle breeds speed in the lion, as lions breed swiftness in the gazelle) are also fought at the cellular and molecular level. Phages attack bacteria, which have defense systems against the phages, which the phages can subvert through their own mechanisms. Crucially, these arms races are surely spurred on by the rapid horizontal gene transfer that occurs between bacteria and canada goose store phages. Bits buy canada goose jacket of bacterial genome can end up in phage genomes, which can then be transferred to new bacteria. In this case, CRISPR was taken up Canada Goose sale by invading phages and turned against its rightful owners, the bacteria themselves a case of turning the gun on its owner.

Interestingly, the GC content of the CRISPR region matched the overall GC content of the phage genome. GC content simply refers to the percentage of a gene or genome that is a G or a C, rather than an A or a T. If the GC content of a gene Canada Goose Parka differs wildly from its neighbors or the genome overall, usually that is a good indication that the gene was recently acquired through horizontal gene transfer. Because the GC content of the viral CRISPR was the same as the rest of the genome, it appears the phages that infect V. cholerae acquired this trick Canada Goose Jackets long ago. Perhaps similar transfers have occurred in other groups of phages, yet to be discovered.