Table 1 Bacterial strains and plasmids used

Strains

Genotype

S. meliloti

GMI211

SmR Nod⁺ Fix⁺

[20]

GMI401

GMI211 asnO::Tn5 SmR NmR

This work

GMI5704

GMI211 fixJ2.3::Tn5 SmR NmR BleoR

[18]

E. coli

ER

asnA31 asnB32 thi

[15]

MM294

Pro-82 thi-1 hsdR17 supE44 endA1

[21]

DH5 α

endA1 hsdR17 (r_k^-mk⁺) supE44 thi-1 recA1 gyrA relA1Δ (lacIZYA-

[29]

argF)U169 deoR (φ 80dlacΔ (lacZ)M15)

Plasmids

pMF457

pGD926 (IncP broad host range vector) derivative carrying a fixK-

lacZ fusion with a mutation in the fixT promoter. TcR

pCHK57

pGMI41211 (Inc-P1 broad host range vector) derivative carrying a

[31]

nifA-lacZ fusion. TcR

pMF11

Same as pMF10 but with fixT in reverse orientation. GmR

pBH1

pBBR1-MCS3 derivative, carrying an HindIII fragment containing

This work

the asnO gene and the SMb20482 orf.

pBasn2

pBBR1-MCS3 derivative, expressing asnO under the control of the

This work

pLac promoter

pUC23

pUC18 digested with EcoRI, carrying the S. meliloti EcoRI

This work

fragment containing the asn O region with the Tn5 insert. Ap^R,

Km^R.

BAC37

pBeloBAC11 containing a 100 kb S. meliloti genome fragment

[26]

carrying the asn-like region of pSymB.

pRK602

PRK600::Tn5, Cm^r, Nm-Km^r

[21]