Table 4. Comparative efficiency of the Ts-sacB system using zeo and kan disrupted allelic exchange substrates in M. chelonae ATCC 35752.
| Transformant | % of XylE− SucR | Number of XylE− | Number of |
| ZeoR or KanR CFUs | CFUs analyzed by | confirmed double | |
| PCR | crossover mutants | ||
| pPR27-4689-ZX | |||
| T1 | 100% | 4 | 3 |
| pPR27-4690-ZX | |||
| T1 | 100% | 4 | 3 |
| T2 | 11% | 4 | 2 |
| pPR27-4691-ZX | |||
| T1 | 49% | 4 | 4 |
| T2 | 29% | 4 | 3 |
| pPR27-4689-KX | |||
| T1 | 100% | 5 | 0 |
| T2 | 74% | 8 | 8 |
| T3 | 100% | 5 | 0 |
| pPR27-4690-KX | |||
| T1 | 100% | 8 | 0 |
| T2 | 99% | 10 | 0 |
| T3 | 100% | 8 | 0 |
| pPR27-4691-KX | |||
| T1 | 100% | 10 | 0 |
| T2 | 100% | 8 | 0 |
One to three transformants (T1, T2 and T3) were selected on plates upon transformation with the pPR27-derived plasmids, grown in 7H9-OADC broth at 30°C for 5 to 7 days, and finally plated onto 7H11-OADC containing Kan or Zeo and 10% sucrose at 37°C. The percentage of CFUs presenting the expected phenotype for allelic exchange mutants at the last selection step of the Ts-SacB procedure (sucrose resistant; KanR or ZeoR and XylE−) is indicated for each construct. Four to ten candidate mutants were analyzed by PCR in each case and the number of double crossover mutants identified is indicated in the last column.