Microorganisms and Disease
Mucus helps in protecting against pathogens by

lowering the pH
sequestering Iron
facilitating the growth of normal flora
blocking access and attachment of pathogens to mucosal surfaces

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Microorganisms and Disease
Cholera toxin is an A-B type toxin in which the B portions bind to a receptor on a host cell and the A portion enters the cell to cause

cleavage of rRNA that results in disruption of ribosome function
ADP ribosylation of a G protein that locks it into an active form that stimulates adenylate cyclase to make cAMP
ADP ribosylation of guanylate cyclase that stimulates production of cGMP
ADP ribosylation of adenylate cyclase that stops production of cAMP

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Microorganisms and Disease
Type III secretion systems are used to inject "effector" proteins directly into a host cell. Salmonella uses a type III secretion system to help the pathogen to

survive the acid pH of the stomach
survive within macrophages
activate T cells to proliferate and secrete cytokines
secrete LT (heat labile toxin) and ST (heat stable toxin) into the lumen of the intestine

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