17. 2011-02-23

Coli infects plant fruit causes fire blight disease

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Unformatted text preview: fruit • Causes “ fire-blight” disease of B.C. orchard fruits. • Secretes extracellular enzyme that digests fruit tissue • Streptomycin sprayed on orchards in large quantities to kill E. amylovora • Streptomycin binds to one of the proteins making-up the small subunit of bacterial ribosomes disrupting translation. • Small protein 124 amino acids • Protein designated RpsL • All bacteria have a rpsL gene encoding a RpsL protein, eg. E. coli • StrS wild-type E. amylovora and StrR mutant E. amylovora exhibit the following differences that can be explained by induced mutation: Wild-type StrS rpsL gene DNA mRNA 43rd codon RpsL protein 43rd amino acid Mutant StrR 5'-AAA-3' Mutation 5'-AGA-3' 3'-TTT-5' 3'-TCT-5' 5'-AGA-3' 5'-AAA-3' Lys Arg • Even though an amino acid in RpsL has been changed by mutation in rpsL, the ribosome still works, streptomycin just doesn’t bind to it. • So bacterium is viable and StrR. “A” base damaged by chemical that removes an amino group. “AD” resembles “G” Parent 1st generation AD C 5’-AAA-3’ 3’-T T T-5’ DNA encoding 43rd codon of rpsL AD T Base-pairing error A T Mismatch Mutation 2nd generation Depends on whether damage repaired G C Mutant StrR A T Wild type StrS A T Wild type StrS Mismatch eliminated Mutation stabilized • Repair of DNA with damaged bases • Example: C base damaged by deaminati...
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This note was uploaded on 10/25/2013 for the course MICB 201 taught by Professor Davidturner during the Fall '12 term at UBC.

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