Table 2.

Efficiency of transformation of MAMT-expressing plasmids into M. tuberculosis Erdman or MGM1995^a

Plasmid	Mean no. of transformants/μg of DNA		MGM1995/WT ratio
	WT (Erdman)	MGM1995
pDB32	316	24,333	77
pDB46	37	0 (2,850)
pMV306Kan	196	2,566	13
pDB90	88	0 (1,150)

^aReintroduction of the six functional MAMT genes (mmaA1, mmaA2, mmaA3, mmaA4, cmaA2, and pcaA) into a strain lacking all of them (MGM1995) by electroporation is lethal. Results of a representative experiment out of three are shown. The WT Erdman strain or MGM1995 was electroporated with either pDB32 (empty episomal plasmid), pDB46 (similar episomal plasmid expressing the above six methyltransferases), an integrating vector (pMV306Kan), or an integrating plasmid expressing the above six methyltransferases (pDB90). A total of 10⁹ bacteria and 500 ng of DNA were used for each electroporation, and the bacteria were plated in several dilutions, allowing for exact estimation of the number of transformants. Each electroporation was done 3 times (in each of the three experiments mentioned above), and the mean number of transformants per μg of DNA is shown. The last column shows the ratio of the number of transformants of MGM1995 to that of WT Erdman, showing the factor by which MGM1995 is more competent. The data in parentheses show the number of transformants of MGM1995 one would expect by the competency derived from control plasmid transformations.