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

Abstract

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.