Table S2.
Bacterial strains used in this study
| Strain | Genotype | Source/reference |
| NiCO21 (DE3) | E. coli NiCO21 (DE3) | New England Biolabs |
| B001 | E. coli DH5α + pRK600 conjugation plasmid, cmR | (25) |
| B100 | S. meliloti RM1021 | (25) |
| B800 | S. meliloti USDA1963 SmR | (12) |
| C237 | A. tumefaciens UBAPF2, RfR | (12) |
| C307 | S. meliloti B800 pHR− (pHRB800−), SmR | (12) |
| C320 | A. tumefaciens UBAPF2 + pHRB800KmR (pJG476), rifR, KmR | (12) |
| C403 | S. meliloti B800 pHR− + pJG505, SmR, TcR | (12) |
| PP233 | A. tumefaciens UBAPF2 + pHRB800GmR (pPP101), RfR, GmR | This study |
| PP236 | S. meliloti B800 + pHRB800 KmR::hrrP (pPP105), SmR, KmR | This study |
| PP316 | S. meliloti C307 + Tn5_hrrP (E62A) (insertion into SM_b21034), SmR, KmR | This study |
| PP317 | S. meliloti C307 + Tn5_hrrP (insertion into SMc03928), SmR, KmR | This study |
| PP337 | S. meliloti B340 (USDA1940 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP338 | S. meliloti B463 (USDA6572 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP339 | S. meliloti B464 (USDA6574 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP340 | S. meliloti B470 (USDA6635 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP341 | S. meliloti B475 (USDA6478 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP342 | S. meliloti B634 (USDA6582 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP344 | S. meliloti B641 (USDA6563 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP345 | S. meliloti B642 (USDA6592 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP346 | S. meliloti B643 (USDA6654 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP347 | S. meliloti B644 (USDA6546 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP348 | S. meliloti B645 (USDA6646 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP349 | S. meliloti B649 (USDA6655 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP350 | S. meliloti C131 (NRG23 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP351 | S. meliloti C285 (USDA6623 SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP352 | S. meliloti C378 (USDA6649 pHRC377− SmR) + Tn5_hrrP, SmR, KmR | This study |
| PP353 | S. meliloti USDA1107 + Tn5_hrrP, SmR, KmR | This study |
| PP354 | S. meliloti USDA1606 + Tn5_hrrP, SmR, KmR | This study |
| PP355 | S. meliloti USDA1617 + Tn5_hrrP, SmR, KmR | This study |
| PP377 | S. meliloti B800GOC + pPP147, TcR, KmR | This study |
| PP389 | S. meliloti B800 + pPP132 (hrrP-GUS), SmR, KmR | This study |
| PP397 | S. meliloti B800 + pPP157 (flaB-GUS), SmR, KmR | This study |
| PP398 | S. meliloti RM1021 + Tn5_hrrP, SmR, KmR | This study |
| PP404 | S. meliloti B800 + pPP156 (nifHDK-GUS), SmR, KmR | This study |
| PP411 | S. meliloti B800 + pPP169 (nifH::KmR), SmR, KmR | This study |
| PP471 | S. meliloti B800 + pPP255 (Ptrp-GUS – rhaK locus), SmR, KmR | This study |