5. do you believe that bacterial production of tyramine has an adaptive signific

Question

5. do you believe that bacterial production of tyramine has an adaptive significance for the bacteria, or is it merely an easily-excreted metabolic end-product, the product of bacterial metabolism of a toxic substance, tyrosine? Briefly defend your answer.

6. TRUE or FALSE (Circle one, please). The milk sickness ‘story’ represents an example of bioactivation. If you circled TRUE, what is the bioactivation step and how is it brought about? If your circled FALSE, defend your answer.

7. Panton valentine leukocidin (PVL) is produced by an organism that’s infamous for its ability to produce necrotizing fasciitis and toxic shock. What is that organism, and how does produce necrotizing fasciitis and shock?

Explanation / Answer

Ans 5: Tyramine is a biogenic amine derived from the microbial decarboxylation of tyrosine with the help of the enzyme tyrosine decarboxylase. Presence of this enzyme is wide spread among all the lactic acid bacteria especially to the genus Enterococcus. Enterococcus occurs in wide range of temperature. Due to their salt and pH tolerance they are particularly competitive when the condition become harsher. The tyrosine decarboxylation pathway contributes to an acid response mechanism in Enterococcus. The pathway gives the strain a competittive advantage in nutrient depleted as well as harsh acidic environmnet for better chance of survival. Therefore bacterial production of tyramine is an adaptive significance for the lactic acid bacteria.

Ans 6: In bioactivation, the enzyme acquire the ability to perform their biologcal fucntion. Milk sickness is caused by Tremetol which is mainly present in leaves and stems of whitesnakeroot plant. Following ingestion of the plant parts the plant components presumably become toxic after microsomal activation by Cytochrome P-450 in the liver. Thus the "milk sickness story" represents an example of bioactivation.

Ans 7: PVL is expressed in Staphylococcus aureus.Staphylococcus are capable of producing exotoxins which act as supersntigens. They interact with antigen presenting cells (APC) by binding to class II MHC moecule and with T cells by binding to specific variable region on the beta chain of the T cell antigen receptor. This induces T cell activation much more higher than normal T cell response. Moreover super antigens cause production of cytokines like TNF-alpha, TNF-beta etc. This leads to the development of capillary leak and shock.

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