I would like to know what the process is by which a bacterium dies by heating, and why some bacteria can withstand a high temperature better than other species. For example, what happens in the cell wall and with the molecules that make up the bacterium? etc.
Answer
Hi Julia,
Death by heating has to do with the denaturing of protein: proteins are long thin threads (of amino acids together) that are twisted in a specific shape. The shape is usually only retained because weak bonds are created between the wires. These weak bonds break at a higher temperature and the protein changes shape: as a result, the activity of the protein also disappears. Enzymes (its proteins) can therefore no longer accelerate (catalyze) reactions. As a result, transport proteins can no longer guide molecules through membranes, and so on. This stops the metabolism (energy (ATP) formation and consumption) in the (bacterial) cell, causing it to die.
At what temperature this happens depends on how many weak bonds, and which (relative strength) are important for the active structure of the protein. Some proteins are stabilized in their structure by forming covalent bonds between the amino acids of the protein threads in addition to the many weak bonds. This requires enzymatic reactions: this is not easy, with weak bonds it is. But covalent bonds are very strong bonds: to break these you have to do a lot more: this way you get much more stable proteins. Bacteria that are thermophilic (that is, like to live at high temperatures) always contain very thermo-resistant proteins. There are therefore numerous applications for proteins from these bacteria: e.g. proteins for washing powders, enzymes for the lab to work at high temperatures (faster reaction or withstand repeated boiling): an example is the enzyme DNA polymerase that is used in PCR (polymerase chain reaction) is used to copy DNA fragments. This enzyme comes from Thermus aquaticus (a bacterium that lives in warm water sources): this is also called Taq-polymerase. This enzyme can withstand at least 40 times 95°C, as is usual in PCR. The 95°C is necessary to pull open the DNA double strand each time in order to make copies. In addition, this Taq polymerase is optimally active at 75°C. All because the bacteria likes to be warm…
Greetings,
Myriam Meyers
KULeuven, Technology Campus Diepenbeek, Industrial Sciences Biochemistry
Answered by
ir. Myriam Meyers
industrial microbiology and biochemistry
Old Market 13 3000 Leuven
https://www.kuleuven.be/
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