Horizontal gene transfer: mechanical mechanism seen (Introduction)

by David Turell , Tuesday, June 12, 2018, 01:26 (2136 days ago) @ David Turell

Just how it picks out the correct DNA portion is still unknown:

https://phys.org/news/2018-06-scientists-bacteria-harpoon-dna-evolution.html

"Using methods invented at IU, researchers recorded the first images of bacterial appendages—over 10,000 times thinner than human hair—as they stretched out to catch DNA. These DNA fragments can then be incorporated into bacteria's own genome through a process called DNA uptake or "horizontal gene transfer."

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"The bacterium used in the study was Vibrio cholerae, the microbe that causes cholera. The bacterial structures used to catch DNA in the environment are extremely thin, hair-like appendages called pili.

"Although scientists were aware that pili play a role in DNA uptake, Dalia said that direct evidence demonstrating how they work was lacking until this study. In order to observe pili in action, the scientists used a new method invented at IU to "paint" both the pili and DNA fragments with special glowing dyes.

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"The new study uses these dyes to reveal that pili act like microscopic "harpooners" that cast their line through pores in the cell's wall to "spear" a stray piece of DNA at the very tip. The pili then "reel" the DNA into the bacterial cell through the same pore.

"Dalia said the pore is so small that the DNA would need to fold in half to fit through the opening in the cell.

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"'It's like threading a needle," said Ellison, who is first author on the study. "The size of the hole in the outer membrane is almost the exact width of a DNA helix bent in half, which is likely what is coming across. If there weren't a pilus to guide it, the chance the DNA would hit the pore at just the right angle to pass into the cell is basically zero."

"Next, Dalia said the team wants to study exactly how pili "hook" onto the DNA at just the right spot, especially since the protein involved in the process appears to interact with DNA in an entirely new way. They also look forward to applying their pili labeling method to study other functions played by these diverse bacterial structures."

Comment: An amazing mechanism which would facilitate evolution. Looks designed to me.