“For Microbes Fighting Viruses, A Fast Response Means a Better Defense.”

“For microbes fighting viruses, a fast response means a better defense”
29 March 2017

Researchers at The Rockefeller University are studying how microbes are using CRISPR to fend off incoming viral threats. CRISPR is important in genome editing and in bacterial immune system. CRISPR operates by obtaining sections of viral DNA that it then catalogs for future recognition. Before this study was conducted, it was unknown as to when the CRISPR started acting on the invading viral DNA. As this research has revealed, CRISPR starts to act upon viral DNA as it is being injected into the bacterium.   The CRISPR takes snippets of the ends of the viral DNA first introduced into the cell. The researchers also tried to modify the spacers of the CRISPR to pick up portions of the end of the viral DNA, and the bacterium struggled to proliferate, indicating that they do in fact grab snippets at the period of initial entry. Grabbing viral DNA at the initial period of entry is essential in recognizing the intrusion early.

We have studied virulence in class and the cycles that viruses utilize to inject and reproduce within their hosts. Two such cycles are the lytic cycle and the lysogenic cycle. Bacteriophages can inject DNA into a host cell. This article also represents “The Red Queen Hypothesis,” in which the bacteria are trying to stay ahead of the virus so they do not meet an early demise.

Critical Analysis:
I have heard of CRISPR being used as a gene editing tool, but I didn’t realize its importance to bacterial immune systems. I also didn’t realize that in order to fend off viruses, the CRISPR would take snippets of the inbound viral DNA and catalog it for later reference. No underestimating the power of microbes!

Why do some bacteria lack CRISPR genes or have very few?

1 Comment for ““For Microbes Fighting Viruses, A Fast Response Means a Better Defense.””



In another class I learned about the biomedical use of crisper to excise, repair, and replace genes that cause disease such as Huntingtons. At the time i thought that it was synthetic, It is really interesting to learn about it’s natural function. I really enjoyed the article, it was clear and concise. If I had written about this article I would have probably asked the same question. This article: https://www.nature.com/news/five-big-mysteries-about-crispr-s-origins-1.21294 has some of the answer. There are some other ways to deal with viral DNA, like restriction enzymes that can excise DNA. So I assume that bacteria that do not have CRISPR either have an analogue performing the same function similarly, or perhaps are proliferate enough to survive as a population through sheer numbers regardless of heavy losses.
Crisper is present in both bacteria and archaea. The spread of this prokaryotic immune system makes one question if it was in their common ancestor, or if its ability to increase fitness, horizontal gene transfer and genetic drift has spread it throughout taxa after they diverged. The article i mentioned before suggests that CRISPR may have originated from transposons.