A possible role of polyamines in the repression of growth of Bradyrhizobium japonicum bacteriods in soybean nodules
1993
Ozawa, T. | Tsuji, T.
Soybean plants (Glycine max L. Merr. cv. Tamahomare) accumulate sufficient putrescine and spermidine in their nodules to inhibit the growth of bacteroids of Bradyrhizobium japonicum strain 138NR. Gas-chromatographic analysis showed that the mature nodules from 35-d-old plants contained approximately 1.5 micromoles each of putrescine and spermidine per g fresh weight. Water-soluble (free) putrescine and spermidine were present at concentrations of 0.39 and 0.13 micromoles per g fresh weight, respectively. Cadaverine and spermine were not detected in the nodules. In a yeast-extract mannitol broth at a pH above 7.0, putrescine, cadaverine, spermidine, and spermine at more than 0.5, 0.2, 0.05, and 0.05 mM, respectively, inhibited the growth of the bacteroids. The effect of the polyamines was bactericidal at higher concentrations. More than 95% of bacteroids were not able to form colonies on agar plates that contained 0.5 mM spermidine at pH 7.0. The high sensitivity to polyamines was a unique characteristic of the bacteroid-form cells of this strain. The bacteroids lost their sensitivity to the polyamines within 24 hours after their isolation from nodules. The cultured cells of this strain multiplied in the presence of 2 mM spermidine or spermine.
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