Biological complexity: bacterial stress protection (Introduction)

by David Turell , Thursday, April 14, 2022, 20:33 (954 days ago) @ David Turell

They need protection from oxidation and nitrogen like all of us:

https://phys.org/news/2022-04-identification-enzyme-involved-stress-bacteria.html

"All organisms, from humans to bacteria, have to be able to respond to a wide range of stresses that result from changes in their environment.

"Common amongst these are so called oxidative and nitrosative stresses, which occur when an organism is exposed to high concentrations of reaction oxygen or reactive nitrogen species, respectively. When this happens, fragile component of the cell are damaged, leading to loss of function and, in some cases, cell death.

"Unsurprisingly, organisms have evolved a multitude of stress response systems that detect and alleviate particular stresses.

"Iron-sulfur clusters, which consist of iron and inorganic sulfur, are found in all cell types where they play essential roles in a wide range of cellular processes. Because they are so reactive, they are often the first cellular components to become damaged under stress conditions. (my bold)

"The di-iron protein YtfE, found widely in bacteria, is generally believed to function directly in the repair of iron-sulfur clusters that have been damaged under stress conditions. This activity has been variably proposed to involve donation of iron for re-building of iron-sulfur clusters, or the removal of nitric oxide (NO) from damaged clusters.

"Recently, new evidence came to light from studies of YtfE function in cells that suggested its activity is associated with an increase, and not a decrease, in the concentration of NO. This prompted researchers in the School of Chemistry to re-examine the function of YtfE.

***

"They showed that YtfE does not efficiently remove NO from damaged iron-sulfur clusters, nor is it an effective donor of iron for cluster assembly.

"The YtfE-catalyzed production of toxic NO from nitrite (NO2-) may seem odd, but YtfE is co-regulated with another enzyme, called Hcp, which functions to detoxify NO (via its reduction to nitrous oxide, N2O).

"The coupled YtfE/Hcp detoxification pathway represents an effective means by which the cell deals with toxic levels of nitrite that can occur under anaerobic conditions."

Comment: bacteria started life long before oxygen was present in any significant amount, so the first very simple bacteria did not require this protection, which was then added later. All makes sense, start with a simple design and improve later. Since this new system had a complex enzyme to do the work, only design fits.