Moreover, a pBBRMCS3 clone constitutively expressing RHE_PE00443 (pTV7) was unable to complement the pantothenate auxotrophy of the panB mutant (data not shown). Table 1 Bacterial strains and plasmid. Strain or plasmid Relevant genotype Reference or source Rhizobium etli     CFN42 Wild type; Nalr [6] ReTV1 CFN42 panC::pTV1; Kmr This study ReTV1-4 CFN42 panC::pTV1 complemented with pTV4; Tcr Kmr This study ReTV1-5 CFN42 panC::pTV1 complemented with pTV5; Tcr Kmr This study ReTV2 CFN42 panB::pTV2; Kmr This study ReTV2 -4 CFN42 panB::pTV2 complemented with pTV4;

Tcr Kmr This study ReTV2 -6 CFN42 panB::pTV2 complemented with OSI-027 concentration pTV6; Tcr Kmr This study ReTV2 -7 CFN42 panB::pTV2 complemented with PTV7; Tcr Kmr This study ReTV3 CFN42 argE::pTV3; Kmr This study CFNX186 CFN42 cured of plasmid p42f; Nalr [18] CFNX186-4 CFNX186 complemented with pTV4; Tcr This study CFNX186-24 CFNX186 complemented with pCos24; Tcr [30] CIAT 652 Wild type; Nalr [38] CIAT 894 Wild type; Nalr [38] Kim5 Wild type; Nalr J. Handelsman, University of Wisconsin, MD IE4771 Wild type; Nalr [15] Escherichia BTSA1 coli     DH5α Host for recombinant plasmids; Nalr Stratagene S17-1 C600::RP4-2(Tc::Mu) (Km::Tn7)

Donor for conjugation [39] Plasmids     pBC pBluescript II SK(+) phagemid vector; Cmr Stratagene. pK18mob pK18, derivative mob; Kmr [29] pRK7813 Broad-host-range cosmid vector; Mob, IncP, Tcr [40] pBBRMCS3 Broad-host-range cloning vector; Mob; Tcr [41] pBC1 pBC harboring a 400-bp BamHI-XbaI PCR fragment of panC; Cmr This study pBC2 pBC harboring a 400-bp BamHI-XbaI PCR fragment of panB; Protein kinase N1 Cmr This study pTV1 pK18mob harboring

a 400-bp KpnI-XbaI PCR fragment of panC; Kmr This study pTV2 pK18mob harboring a 400-bp KpnI-XbaI PCR fragment of panB; Kmr This study pTV3 pK18mob harboring a 400-bp KpnI-XbaI PCR fragment of argE; Kmr This study pTV4 pRK7813 harboring a 3.1 kb EcoRI fragment of pCos24 containing panC and panB; Tcr This study pTV5 pBBRMCS3 harboring a 1.2 kb KpnI-XbaI PCR fragment containing panC; Tcr This study pTV6 pBBBRMCS3 harboring a 1 kb KpnI-XbaI PCR fragment containing panB; Tcr This study pTV7 pBBRMCS53 harboring a 1 kb KpnI-XbaI PCR fragment containing RHE_PE00443; Tcr This study pcos24 20 Kb EcoRI fragment of plasmid p42f cloned in pLAFR1 containing panC, panB, oxyR and katG; Tcr [30] Figure 1 Pantothenate auxotrophy of R. etli CFN42 panC and panB mutants. Growth of the R. etli CFN42 wild-type strain and its derivative panC (ReTV1) and panB (ReTV2) mutants in: (a) minimal medium, (b) minimal medium supplemented with 1 μM calcium pantothenate. Values represent the means of three independent experiments; error bars show standard deviations. Plasmid pTV4, harboring the panC and panB genes, as well as plasmids pTV5 and pTV6, carrying only panC or panB respectively, were introduced into mutant strains ReTV1 and ReTV2 and the growth phenotype of each construction was evaluated in MM.