Analysing the growth of antibiotic-resistant CRISPR-transformed Escherichia coli under different concentrations of streptomycin.


  • Parsa M Alizadeh
  • Gabriel Costa
  • Beenish Fatima
  • Chang Wei


We set out to explore if Escherichia coli transformed with CRISPR/Cas9 to become
resistant to the antibiotic streptomycin will present different growth levels(total number of
colonies) to different concentrations of streptomycin in their agar plates. We plated the
transformed and untransformed E.coli in separate Petri-dishes containing 0, 25, and 50 ug/ml of
streptomycin. Each of these treatments was repeated 3 times(for the sake of statistical
significance) for a total of 18 plates. We observed a total of 4 colonies of transformed E.coli
growing in the plates containing 50 ug/ml of streptomycin. We also observed bacterial lawns in
all of our 18 plates. The lawn growth in all of our plates is due to a contaminating bacteria
unidentified to date. We hypothesize that this bacteria is not affected by streptomycin, and the
fact that this bacteria grew lawns in all of our plates rendered our experiment to be skewed by an
unaccounted factor. We therefore cannot conclude if E.coli transformed with CRISPR/Cas9 to
become resistant to streptomycin grows at the same rate regardless of the antibiotic’s
concentration, since the E.coli growth may have been limited by the growth of the unknown
bacteria due to less available space and nutrients.