Genetics Lab Exp 2 Report

Topics: Escherichia coli, Agar plate, Enterobacteriaceae Pages: 4 (1312 words) Published: May 12, 2012
Experiment 2
The induction of mutations in Escherichia coli by ethyl methane sulfonate and in Salmonella typhimurium by Tn10 The purpose of this experiment was to identify and isolate ethyl methane sulfonate (EMS) mutagenized colonies of Escherichia coli (lac-) which could no longer use lactose as a carbon source and to isolate Tn10 mutagenized colonies of Salmonella typhimurium which were induced auxotrophs and identify independent mutations. Results

Mutants observed in Escherichia coli:
Control 10-5 Dilution: 0/440
Control 10-6 Dilution: 0/310
Mutagenized 10-5 Dilution: 9/339
Mutagenized 10-6 Dilution: 23/ 403
A hypothesized E.coli mutant colony (opaque and white colony) from the EMS mutagenized plate was streaked on a new MacConkey’s agar plate using three clean toothpicks. After overnight incubation, the plate streaks contained only pink colonies. Mutants observed in Salmonella typhimurium:

100 colonies from the Tn10 mutagenized S. typh 10-5 and 10-6 dilution and 100 colonies from the control 10-5 and 10-6 dilutions were gridded and scored on minimal agar followed by nutrient agar. The number of colonies that did not grow on minimal agar but grew on the nutrient agar: Control S. Typh colonies with no growth on minimal= 0/100

Mutagenized S. Typh colonies with no growth on minimal= 10/100 The ten hypothesized auxotrophs from the mutagenized S. Typh plates were replica plated onto minimal agar followed by 9 pool plates and nutrient agar control plate. Growth of each hypothesized auxotroph on each plate: HypothesizedAuxotroph| Min Agar| Pool 1| Pool 2| Pool 3| Pool 4| Pool 5| Pool 6| Pool 7| Pool 8| Pool 9| LB agar| *Control| Yes| Yes| Yes| Yes| Yes| Yes| Yes| Yes| Yes| Yes| Yes| 1| -| -| -| -| Yes| -| -| Yes| -| -| Yes|

2| -| -| -| -| Yes| -| -| Yes| -| -| Yes|
3| -| -| -| -| Yes| -| -| Yes| -| -| Yes|
4| -| -| -| -| Yes| -| -| Yes| -| -| Yes|
5| -| -| -| -| Yes|...
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