Additionally, we replaced the eUNG in CGBEevolve with an orthologous UNG from M. smegmatis (mUNG) to facilitate C-to-G conversions in M. smegmatis (Fig. ). Four versions of C-to-G base editors with the fusion of eUNG or mUNG to the C or N terminus of the St1Cas9 protein were constructed for base editing in M. smegmatis. We found that fusion of mUNG or eUNG to the C terminus of St1Cas9 gave similar editing efficiencies at all the tested sites, whereas fusion of mUNG or eUNG at the N terminus did not yield efficient C-to-G editing (Fig. ). Given the similar editing efficiency using mUNG or eUNG, we kept eUNG in CGBEevolve for further characterization.