Choline and Glycine Betaine Uptake in Various Strains of Rhizobia Isolated from Nodules of Vicia faba var. major and Cicer arietinum L.: Modulation by Salt,Choline, and Glycine Betaine |
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Authors: | Fatiha Brhada Marie-Christine Poggi Daniel Le Rudulier |
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Institution: | (1) Laboratoire de Microbiologie et Biologie moléculaire, Département de Biologie, Faculté des Sciences, Université Mohammed V, BP 1014, Rabat, Maroc , MA;(2) Laboratoire de Biologie végétale et Microbiologie, URA CNRS 1114, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cédex, France , FR |
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Abstract: | Two strains of Rhizobia isolated from nodules of Vicia
faba var. major and one strain isolated from nodules of Cicer
arietinum L. were characterized for salt resistance. The presence of 1 mM
glycine betaine or choline in a minimal medium with added NaCl had a
beneficial role on the growth of the three strains. Both molecules were found
to be taken up by cells obtained at low osmolarity, and whereas glycine
betaine uptake activity was stimulated significantly in cells grown in the
presence of 0.15 M NaCl, choline uptake activity was strongly inhibited by
salt in all tested strains. However, in cells grown with exogenous choline,
the uptake inhibition exerted by salt was relieved, mainly in the strain
isolated from nodules of C. arietinum L. On the basis of kinetics
determinations, in control cells as well as in salt-stressed cells, only
high-affinity activities were observed for glycine betaine and choline
(apparent K
m
s between 3 and 18 μM). Periplasmic proteins
that bound glycine betaine or choline were identified. In nondenaturing
conditions, these proteins extracted from the various strains showed
different electrophoretic mobility with always a less negative entire charge
than the analogous proteins from Rhizobium meliloti.
Received: 29 July 1996 / Accepted: 10 September 1996 |
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Keywords: | |
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