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When a large distance separates the source and the target (a small activation site), the redundancy principle explains that this geometrical gap can be compensated by large number. Had nature used less copies than normal, activation would have taken a much longer time, as finding a small target by chance is a rare event and falls into narrow ...
Some bacteria, such as Streptococcus pyogenes, Staphylococcus aureus and Pseudomonas aeruginosa, produce a variety of enzymes which cause damage to host tissues.Enzymes include hyaluronidase, which breaks down the connective tissue component hyaluronic acid; a range of proteases and lipases; DNases, which break down DNA, and hemolysins which break down a variety of host cells, including red ...
Pseudomonas aeruginosa, is an AHL-producing bacteria an opportunistic pathogen that infects immuno-compromised patients, [23] and is found in lung infections of cystic fibrosis patients. P. aeruginosa relies on quorum sensing via production of lactones N -butanoyl- L -homoserine (C4-HSL) and N -(3-oxododecanoyl)-l-HSL (3-oxo-C12-HSL) to ...
FimH is a bacterial adhesin that helps bacteria such as Escherichia coli to bind to host cells and their receptors (here: the human proteins CD48 and TLR4, or mannose residues). [ 4 ] Most fimbria of gram-negative bacteria function as adhesins, but in many cases it is a minor subunit protein at the tip of the fimbriae that is the actual adhesin.
Many bacteria produce virulence factors that inhibit the host's immune system defenses. For example, a common bacterial strategy is to produce proteins that bind host antibodies. The polysaccharide capsule of Streptococcus pneumoniae inhibits phagocytosis of the bacterium by host immune cells. [citation needed] Toxins
A viral infection does not always cause disease. A viral infection simply involves viral replication in the host, but disease is the damage caused by viral multiplication. [5] An individual who has a viral infection but does not display disease symptoms is known as a carrier. [17] Mechanisms by which viruses cause damage and disease to host cells
The pathogenic mechanisms of a disease (or condition) are set in motion by the underlying causes, which if controlled would allow the disease to be prevented. [5] Often, a potential cause is identified by epidemiological observations before a pathological link can be drawn between the cause and the disease.
During the lysogenic cycle, the virus genome is incorporated as prophage and a repressor prevents viral replication. Nonetheless, a temperate phage can escape repression to replicate, produce viral particles, and lyse the bacteria. [13] The temperate phage escaping repression would be a disadvantage for the bacteria.