The Antibiotic Streptomycin Binds to the 30S Subunit in Bacteria

question 45

Essay

The antibiotic streptomycin binds to the 30S subunit in bacteria and interferes with translation. Streptomycin resistance (SmR) can occur through mutation in the rpsL gene, which encodes the ribosomal protein S12. The antibiotic can no longer bind to the altered protein, so translation can occur without interference from the antibiotic. However, in the absence of streptomycin, many SmR strains of bacteria grow less well than the non-mutant streptomycin-sensitive (SmS) bacteria.
a. Propose a model for why SmR bacteria grow better than SmS bacteria in the presence of streptomycin but not as well in the absence of streptomycin.
b. During translation, an incorrect amino acid is occasionally incorporated into the polypeptide chain-that is, the amino acid added does not correspond to the codon at that location in the mRNA. You develop an assay that can assess this rate of incorrect amino acid incorporation and thereby estimate the accuracy of translation in bacteria. You find that SmR bacteria are more accurate than SmS bacteria in this experiment. How might this observation affect your model above?

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Definitions:

Sharecropping Contract

An agricultural system prevalent after the Civil War where landowners allowed tenants to use the land in return for a portion of the crops produced on their portion of land.

Economic Slavery

Describes a condition where individuals are so financially indebted or economically constrained that they have no choice but to work for minimal pay, effectively being bound to their employers.

Ex-Slave

A person who was formerly enslaved but has since gained freedom, either through legal emancipation, escape, or the end of slavery as an institution.

Abraham Lincoln

The 16th President of the United States, who led the country during the Civil War and issued the Emancipation Proclamation.