Figure 3.

Characterization of mutant phenotype revertants and isolation of a stable METE insertion mutant (a) A non-reverting colony (i) alongside three independent revertant colonies (ii–iv) visualized under a dissecting microscope, after 11 days on solid medium −B₁₂. (b) PCR screen for the presence of GR-TE insertion in METE gene of clones using primers spanning GR-TE insertion site (METE_revert F1/R1). Clone no. 7 is vitamin B₁₂ dependent yet lacks the GR-TE (expected product sizes: wild-type METE− 913 bp, and METE with GR-TE insertion 913 bp+246 bp=1159 bp). Sequencing revealed a 9-bp footprint (CACCATGCT) in this clone (c) the latter 6 bp of which (underlined grey) is a remnant of the METE repeat.