Ch. 5A: Transforming Bacteria with Recombinant Plasmids

Learning goals Describe the role of transformation in the gene cloning process Explain the purpose of each control in the transformation experiment Explain how the information encoded in a gene is expressed as a trait

Key Ideas A recombinant plasmid must be taken up by bacteria bacteria cell machinery used to replicate and to express the gene of interest. If transformed with the pARA-R plasmid bacteria can be identified Ampicillin will prevent the growth of cells that do not carry an ampicillin resistance gene Arabinose will activate the bacteria promoter that controls expression of the rfp gene.

Go to pg 76 and complete Lab 5A Transforming Bacteria with the pARA-R PlasmidTransforming Bacteria

RFP expression araC generfp geneP BAD Transcription mRNA Translation araC protein Biotech Experience

RFP expression rfp geneP BAD araC protein araC gene araC protein prevents RFP transcription by causing a loop to form in the region of the fp gene r Biotech Experience

RFP expression araC protein arabinose araC generfp geneP BAD arabinose – araC protein complex RNA polymerase Arabinose – araC protein complex prevents DNA looping and helps to align RNA polymerase on the promoter site (P BAD ). mRNA Transcription Translation RFP (red fluorescent protein) Biotech Experience

Plating Tips Note the plate markings: I=LB, II=LB/amp, III=LB/amp/ara Label the bottom of the plate near the edge Open the plates like clam shells Sample goes on the agar, not the lid

More Plating Tips Agar is like jello, firm but not invincible, be gentle – the “spreader is not a shovel Turn the plates upside down (lids down) for incubation, stacked and taped together After incubation, do not open plates, observe through the bottom

Remind Students 1. Sterile technique Using bacteria Contamination may affect results 2. Carefully READ and FOLLOW the lab protocol. Be sure lab partners communicate 3. No Food or Drinks

Sterile technique  Always follow the protocol carefully – know what you’re doing  Work quickly. Less time = Less opportunities for contamination  Do not leave any container (tube, plate) open any longer than needed  Watch what your equipment touches – there is no “5 second rule” here.  All tips, tubes and spreaders go in the “contaminated waste” container

DO NOT open plates, observe by viewing through the bottoms Used plates – dispose in the “contaminated waste” bags LB P-P+ LB/amp LB/amp/ara P-P+

“oops” plates

Satellite colonies Some cells without antibiotic resistance do become "freeloaders" and survive because other cells are doing the work of destroying the antibiotic in their immediate vicinity on the plate. They only develop with antibiotics such as ampicillin, that are destroyed by enzymes such as beta lactamase outside of the cell.

Why do we get satellite colonies?  The ampicillin plate is old (meaning that the antibiotic is partially degraded)  The transformed cells are plated at very high density (meaning that the plate is covered with huge number of cells)  The copy number of the plasmid in the cells is so high that beta lactamase is secreted at high levels,  The colonies grow on the plate for several days (allowing more time for degradation).