Homospermidine is required for normal growth in R. leguminosarum. A, the effect of the specific ODC inhibitor α-DFMO on growth of R. leguminosarum in minimal defined medium, monitored by optical density. Error bars in panels A–C and E indicate S.E. B, quantified polyamine content of R. leguminosarum cells grown in 5 mm α-DFMO-containing minimal medium and sampled after 24 and 48 h of growth. C, growth of R. leguminosarum in minimal medium containing: black circles, control cells; black squares, 5 mm α-DFMO; asterisks, α-DFMO and 1 mm cadaverine; white circles, α-DFMO and 1 mm norspermidine; white squares, α-DFMO and 1 mm spermidine; black triangles, α-DFMO and 1 mm putrescine. D, polyamine profile, detected by HPLC, of R. leguminosarum cells grown in minimal medium containing 5 mm α-DFMO and 1 mm putrescine (PUT), norspermidine (NSPD), spermidine (SPD), or cadaverine (CAD) with a peak R representing the labeling reagent and a peak of homospermidine (HSPD). E, growth of R. leguminosarum cells in minimal medium containing: black circles, control cells; black squares, 5 mm α-DFMO; black triangles, 5 mm α-DFMO and 0.5 mm homospermidine; white circles, 5 mm α-DFMO and 0.5 mm spermidine; white squares, 5 mm α-DFMO and 0.5 mm norspermidine. F, polyamine profile, detected by HPLC, of R. leguminosarum cells grown with: black trace, control cells; gray trace, 5 mm α-DFMO; red trace, 5 mm α-DFMO and 0.5 mm norspermidine; green trace, 5 mm α-DFMO and 0.5 mm spermidine; blue trace, 5 mm α-DFMO and 0.5 mm homospermidine. DAP, diaminopropane; PUT, putrescine; R, labeling reagent; NSPD, norspermidine; SPD, spermidine; HSPD, homospermidine.