User:Sagesanders17/Bacterial stress response

The bacterial stress response enables bacteria to survive adverse and fluctuating conditions in their immediate surroundings. Various bacterial mechanisms recognize different environmental changes and mount an appropriate response. A bacterial cell can react simultaneously to a wide variety of stresses and the various stress response systems interact with each other by a complex of global regulatory networks.

Bacteria can survive under diverse environmental conditions and in order to overcome these adverse and changing conditions, bacteria  senses the changes and mount appropriate responses in gene expression and protein activity. The stress response in bacteria involves a complex network of elements that acts against the external stimulus. Bacteria can react simultaneously to a variety of stresses and the various stress response systems interact (cross-talk) with each other. A complex network of global regulatory systems leads to a coordinated and effective response. These regulatory systems govern the expression of more effectors that maintain the stability of the cellular equilibrium under various conditions.

Stress response systems can play an important role in the virulence of pathogenic organisms.

There are regulatory systems that respond to changes in temperature, pH, nutrients, salts, and oxidation. The response level is based on the amount of change that occurs in the environment. The response is highest when changes occur under stress conditions, in this case the control networks are called stress response systems. These systems are very similar within prokaryotes and some of the systems, specifically the heat shock response, are conserved in eukaryotes and archaea. While the systems are extremely similar, the conditions under which they are activated differ greatly from organism to organism. The systems that activate the response to environmental change have many control elements. These control elements can be specific to one gene or they can control a large group of genes. When control elements control a large group of genes it is called a regulon. A regulon is a group of genes that are all regulated by the same control pattern. A stimulon is all the genes who express responses to the same condition. The control elements also regulate the expression of genes during various environmental conditions including starvation, sporulation and others.

In bacteria some of the most important stress response systems are:


 * Heat shock response, controlled by the sigma factor sigma 32
 * Envelope stress response, controlled mainly by the sigma factor sigma E and the Cpx two-component system
 * Cold shock response, which governs expression of RNA chaperones and ribosomal factors
 * General stress response, which depends on the sigma factor sigma
 * (p)ppGpp-dependent stringent response, which reduces the cellular protein synthesis capacity and controls further global responses upon nutritional downshift.
 * Virulence of bacteria and stress responses

Heat Shock Response[edit]
Heat Shock Response helps to stop any damage to the cellular process in high temperature conditions. It is also caused because the heat allows for the proteins to be transcriptionally upregulated which also helps to protect the bacteria from protein denaturation. Heat proteins are created by factors of heat-shock promoters. Some heat proteins that are created are chaperones and proteases. This means that the protein will be folded the correct way as well as position in the right portions of the cell. It also ensures that any protein that is not folded correctly will be destroyed properly to ensure that the bacteria remains to function properly.

Envelope Stress Response[edit]
The two-component signal transduction (2CST) system also allows the bacterial cell to be able to sense stress in the system. This is due to a histidine kinase that can be found in the cell's inner membrane, to detect the stress. It is able to detect the stress because of autophosphorylation that happens when the stress is detected. Once the stress is detected, the system moves to a cytoplasmic response regulator. This is due to the cell being in a phosphate group, but this new response regulator will start to act like a transcription factor. This means that it will start to change what is expressed when looking at the genes. This is especially true when looking at the Cpx proteins which help to prevent the protein from folding the wrong way or not at all. Cpx proteins also help to ensure that there will be no other damage when looking at other cellular processes.

Cold Shock Response[edit]
When bacteria is in an area of very low and cold temperature, they will have a five hour long phase that will cause them not to grow at all. The way the bacteria tries to adapt is by creating child shock proteins that will be transcription factors that will be upregulated during the five hour phase. Once this five hour period ends, the bacteria will start to grow again, but it will be at a very slow rate. These proteins will help for the bacteria to continue to grow and survive at the lower temperatures. A protein called CspA was originally found in E. coli and is known to be one of the first cold shock proteins discovered and is known to be a single-stranded RNA. This will ultimately help with transcription and translation. With cold shock proteins, It is not just transcription and translation. You can also see that there can be condensation of the chromosome that occurs. This means that the cells will prematurely go onto the interphase stage of mitosis. There will also be an organization of the nucleoid which is when the intracellular and extracellular factors in the cell. And lastly, there is an enhancement when it comes to the survival of bacteria which helps the cell to get the food and nutrients it needs to survive.