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The ribosome is the cellular structure responsible for protein synthesis and is the target of certain antibiotics in bacteria. All peptides leave the ribosome through a region called the exit tunnel, which is composed of proteins and rRNA. Interactions between peptides exiting the ribosome and the component of the exit tunnel called the constriction site can be a determining factor in whether gene expression will continue. Previous research efforts have found that SVS1144 Escherichia Coli (E. coli) experience a decrease in expression of the lysine-dependent acid-resistance gene CadB when the cells possessed the K90D mutation, in which the 90th residue of the ribosomal protein UL22 is switched from a lysine to an aspartic acid. This project aimed to record how CadB expression was affected by the presence of the K90D mutation in SVS1144 E. coli, as well as in MG1655 Δ7 E. coli carrying the +Ains mutation in 23S rRNA. Both bacterial strains were transformed with two types of plasmids carrying a green fluorescent protein (GFP) reporter gene. One plasmid was a transcriptional fusion plasmid and the other was a protein fusion plasmid. Detection of GFP was achieved using confocal microscopy and western blotting. Results from confocal microscopy persistently showed a decrease in transcriptional activity among SVS1144 bacteria with the K90D mutation compared to the wild type cells and no significant difference in any expressional activity between wild type and +Ains cells of MG1655 Δ7. Preliminary data from western blotting yielded mixed results and will need further testing.


Research and Creative Experience for Undergraduates (RCEU)


Biological Sciences

College Name

College of Science


Luis Cruz-Vera

Publication Date


Document Type



Ribosome, Exit tunnel, UL22, 23S rRNA, CadB, GFP, gene regulation

Describing the effects of antibiotic-resistance ribosomes on gene expression in bacteria



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