Miscellany: survival in bacteria (General)

by David Turell @, Tuesday, April 13, 2021, 18:34 (483 days ago) @ David Turell


DAVID: Just opposite: species survive because of God's designs. Survival struggles do not drive evolution.

dhw: It is not the opposite! It is purpose and result: according to your theory, your God wanted organisms to survive, and so he designed ways in which they could survive, and so they survived because of his designs. The purpose of the evolutionary innovations was to enable organisms to survive – totally in keeping with Darwin’s theory.

DAVIDAbsolutely no!!! "Evolutionary innovations" advanced evolution from bacteria. God's new designs drive evolution forward.

Bacteria when likely to explode have an escape valve:


"Almost all bacteria rely on the same emergency valves—protein channels that pop open under pressure, releasing a deluge of cell contents. It is a last-ditch effort, a failsafe that prevents bacteria from exploding and dying when stretched to the limit.


"'We were actually able to see the entire cycle of the protein channel passing through a series of functional stages," Walz says.

"Walz has long focused upon MscS, a protein embedded in bacterial membranes that opens in response to mechanical force. MscS proteins exist in a closed state while resting in a thick membrane. Scientists once suspected that, when fluid build-up causes the cell to swell and puts tension on the membrane, it stretches so thin that its proteins protrude. Thrust into an unfamiliar environment, the protein channels snap open, releasing the contents of the cell and relieving pressure until the membrane returns to its original thickness and its channels slam shut.

"But when Yixiao Zhang, a postdoctoral associate in the Walz group, tested this theory over five years ago, reconstituting MscS proteins into small custom-designed membrane patches, he discovered that it was impossible to prise the channel open by thinning membranes within the natural range. "We realized that membrane thinning is not how these channels open," Walz says.

"These custom patches, called nanodiscs, allow researchers to study proteins in an essentially native membrane environment and to visualize them with cryo-electron microscopy. Walz and Zhang resolved to push the limits of nanodisc technology, removing membrane lipids with β-cyclodextrin, a chemical used to excise cholesterol from cell cultures. This induced tension in the membrane, and Walz and his team could observe with cryo-electron microscopy as the channel reacted accordingly—eventually snapping closed for good, a phenomenon known as desensitization.

"What they observed matched computer simulations, and a new model for the function of MscS emerged. When fluid builds up inside the cell, they found, lipids are called in from all corners to help ease tension throughout the membrane. If the situation becomes dire, even lipids associated with the MscS channels flee. Without lipids keeping them closed, the channels have the legroom to pop open.

"'We could see that, when you expose the membranes to β-cyclodextrin, the channels open and then close again," Walz says.

"Walz and Zhang's new method of manipulating nanodiscs with β-cyclodextrin will allow researchers studying dozens of similar mechanosensitive protein channels to, at long last, test their hypotheses in the lab. Many such proteins play key roles in humans, from hearing and sense of touch to the regulation of blood pressure."

Comment: In evolution what is invented in the past is used in the present, so the 99% gone directly relate to humans. Also this study shows how survival is guaranteed by design, which had to be present in the first bacterial designed organisms.

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