Biological complexity: bacterial defend against virus (Introduction)

by David Turell , Sunday, March 05, 2017, 18:15 (2601 days ago) @ David Turell

They chop up its DNA while defending their own DNA:

http://alliance.nautil.us/feature/155/the-man-who-kicked-off-the-biotech-revolution?utm...

"Wilcox suggested to Smith that the bacteria were destroying the viral DNA. He based his suggestion on a hypothesis proposed a few years earlier by Werner Arber, a microbiologist at the University of Geneva. Arber speculated that enzymes could restrict the growth of viruses by chopping up their DNA, and dubbed these hypothetical molecules “restriction enzymes.”

"Arber recognized that if restriction enzymes went on an unchecked rampage, they could kill the bacteria themselves by chopping up their own DNA. He speculated that bacteria were shielding their own DNA from assault, and thus avoiding suicide, by covering their genes with carbon and hydrogen atoms—a process known as methylation. The restriction enzymes couldn’t attack methylated DNA, Arber proposed, but it could attack the unprotected DNA of invading viruses.

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"Matthew Meselson and Robert Yuan at Harvard University reported in the paper how they had discovered a protein in E. coli that cut up foreign DNA—in other words, an actual restriction enzyme. With that paper fresh in his mind, Wilcox suggested to Smith that they had just stumbled across another restriction enzyme in Haemophilus influenzae.

***

"Once Smith and his colleagues published the remarkable details of their restriction enzymes, other scientists began to investigate them as well. They didn’t just study the enzymes, though—they began employing them as a tool. In 1972, Paul Berg, a biologist at Stanford University, used restriction enzymes to make cuts in the DNA of SV40 viruses, and then used other enzymes to attach the DNA from another virus to those loose ends. Berg thus created a single piece of DNA made up of genetic material from two species.

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" Companies sprouted up that were dedicated to using restriction enzymes to modify DNA. The first commercial application of this technology came from Genentech, a company founded in 1976. Genentech scientists used restriction enzymes to create a strain of E. coli that carried the gene for human insulin. Previously, people with diabetes could only purchase insulin extracted from the pancreases of cows and pigs. Genentech sold insulin produced by swarms of bacteria reared in giant metal drums.

"Over the years, scientists have built on Smith’s initial successes by finding new tools for manipulating DNA. Yet even today, researchers make regular use of restriction enzymes to slice open genes. “They’re still absolutely crucial,” said Carlson. “If you want to put a specific sequence of DNA in another sequence, it’s still most often restriction enzymes that you use to do that.'”

Comment: the subject of this entry is a single scientist's research and how it resulted in a whole biotech industry working with DNA. My take is on the genome complexity of bacteria and how they defend themselves with specialized enzymes, giant molecules that must be discovered by the bacteria in order to deploy them and defend their own DNA by learning to deploy methyl radicals to protect their own DNA. Not by chance, only by design.