Team:Paris Bettencourt/Results

CRISPR anti-Kan plasmids target kanamycin resistant E. coli. WT (blue) and a kanamycin resistant strain (KanR, red) were co-transformed with a plasmid carrying the Cas9 construct, and a second plasmid carrying the anti-Kanamycin gRNA. WT was successfully transformed with one or both plasmids. KanR E. coli couldn’t be tranformed with both plasmids because of Cas9-induced cleavage of the chromosome specifically at the KanR cassette, with about 99% efficiency.

MycoSIR E. coli depend on our synthetic pathway for growth. E. coli strain BL21(DE3) was deleted for cysI and transformed with the three genes of the mycoSIR pathway expressed from IPTG-inducible T7 promoters (red). Wild-type (blue), uninduced (purple) and pathway-minus (gold) strains were used as controls. Both time course growth curves (A) and final ODs (B) reveal that the complete, induced pathway is required for growth

FTDMH expression kills mycobacteria in culture. We mixed E. coli and WT M.smegmatis in LB media. Plating assays were used to count specifically M. smegmatis after the indicated times. When TDMH-expression was fully induced, more than 98% of mycobacteria were killed after 6 hours (red line). Populations of mycobacteria alone (black line) and mycobacteria mixed with uninduced E. coli (blue line) were stable.

Our synthetic phage conveys antibiotic-sensitivity to an antbiotic-resistant population. WT and chloramphenicol resitant strains (1 mL at OD 0.7) were infected with 10 ul of collected phage. Cells were plated at various antibiotic concentrations to measure sensitivity. (A) The anti-Cm phage system effectively killed 99.1% of the population at 1 mg/mL of Chloramphenicol. (B) Of the surviving cells, 70% still carried the GFP phage marker. This suggests that 70% of system failure originates from resistance to the siRNA, and 30 originates from resistance to the phage.