Only $2.99/month

Lec 9: Determinants of Infectious Disease 2 (AB)

Terms in this set (20)

-Bind host proteins, e.g. fibronectin, albumin (e.g. M protein Strep. Pyogenes-->so not detected as 'foreign')
-Produce surface protein which binds antibodies 'backwards' (e.g. protein A--Staph. Aureus or protein G--Strep. pyogenes)
=Prevents opsinisation

To explain this more, from wiki:
-Protein A=surface protein originally found in the cell wall of the bacteria Staphylococcus aureus. It has found use in biochemical research because of its ability to bind immunoglobulins. It is composed of five homologous Ig-binding domains that fold into a three-helix bundle. Each domain is able to bind proteins from many mammalian species, most notably IgGs. It binds the heavy chain (i.e. trunk of the 'Y' shape aka the 'Fc' region) within the Fc region of most immunoglobulins.
-Through these interactions in serum, where IgG molecules are bound in the wrong orientation (in relation to normal antibody function (since the antigen-antibody binding site is actually on the arms of the 'Y' chain aka the 'Fab' region), the bacteria disrupts opsonization and phagocytosis.
-So imagine when it's correctly able to be opsonised=bacteria surrounded by 'Y' on surface where branches attach to membrane. But when anti-ospinisation with protein A from S.Aureus, imagine bacteria with lots of protein A on the surface membrane, with the 'Y' attached by the trunk instead=backwards.
-Opsinisation=enhances phagocytosis by marking an antigen for an immune response. The Fab region of the antibody binds to the antigen, whereas the Fc region of the antibody binds to an Fc receptor on the phagocyte, facilitating phagocytosis
-(The Fab region of the antibody determines antigen specificity while the Fc region of the antibody determines the antibody's class effect. )
-Many (pathogenic) bacteria only produce virulence factors until a quorum (minimal number) of cells is present
-Vibrio fisheri=Lux genes
-Pseudomonas aeruginosa=haemolysin, switch motile to biofilm

^To explain above, internet:
-Bacteria that use quorum sensing constitutively produce and secrete certain signaling molecules (called autoinducers or pheromones). These bacteria also have a receptor that can specifically detect the signaling molecule (inducer). When the inducer binds the receptor, it activates transcription of certain genes, including those for inducer synthesis. There is a low likelihood of a bacterium detecting its own secreted inducer. Thus, in order for gene transcription to be activated, the cell must encounter signaling molecules secreted by other cells in its environment. When only a few other bacteria of the same kind are in the vicinity, diffusion reduces the concentration of the inducer in the surrounding medium to almost zero, so the bacteria produce little inducer. However, as the population grows, the concentration of the inducer passes a threshold, causing more inducer to be synthesized. This forms a positive feedback loop, and the receptor becomes fully activated. Activation of the receptor induces the up-regulation of other specific genes, causing all of the cells to begin transcription at approximately the same time. This coordinated behavior of bacterial cells can be useful in a variety of situations. For instance, the bioluminescent luciferase produced by Vibrio fischeri would not be visible if it were produced by a single cell. By using quorum sensing to limit the production of luciferase to situations when cell populations are large, V. fischeri cells are able to avoid wasting energy on the production of useless product.
-The bioluminescence of V. fischeri is caused by transcription of the lux operon, which is induced through population-dependent quorum sensing.[1] The population of V. fischeri needs to reach an optimal level to activate the lux operon and stimulate light production.
-V. fischeri is one of many species of bacteria that commonly form symbiotic relationships with marine organisms. Marine organisms contain bacteria that use bioluminescence so they can find mates, ward off predators, attract prey, or communicate with other organisms. In return, the organism the bacteria are living within provides the bacteria with a nutrient-rich environment