Eur. J. Soil Biol., 1998, 34 (2), 99-104 0 Elsevier, Paris Growth and siderophore production in vitro of Bradyrhizobium (Lupin) strains under iron limitation Mohamed Hemida Abd-Alla Institute of Plant Nutrition, Justus-Z,iebig univevsity, Sudanlage 6, 35390 Giessen, Germany. cfax: +49 641 99 391 69; e-mail: Mohamed H.ibd-Alla@ernaehrung.uni.giessen.de) Received September 1.5, 1998; accepted January 5, 1999. Abstract - Six Bradyrhizobium (lupin) strains were evaluated for their ability to produce in vitro siderophores using four chemical assays. Brudyrhizobium strains WPBS 3201 D and 3211 D gave positive reactions with the chrome azurol S assay (CAS) and produced hydroxamate-type siderophores. The other four strains (USDA 3040, 3041, 3042 and CB 2272) gave negative results for siderophore production with the four assays. The generation time, growth yield and hydroxamate production of strain WPBS 3201 D were affected by the iron concentration of the culture medium and the previous culture history of the cells. Resuspension of washed cells grown previously in media supplemented with 0 and 20 pm01.L~’ Fe into differing iron regimes (0 and 20 umol.L-’ Fe) sug that the extent of hydroxamate production was dependent on the growth history of the cells. Cells pre-grown in 20 prnolL B est Fe produced a high amount of hydroxamates compared with cells pre-grown in iron-free medium when resuspended in medium containing u 0.5 pmol.L- P 4 pmol.L-’ Fe. Cells pre-grown in 20 pmol.L-’ Fe were also more sensitive to iron repression than those pre-grown in Fe. Mannitol was the best carbon source for siderophore production. Siderophore synthesis was inhibited by 4-chlo- romercuribenzenesulfonic acid, 2,4-dinitrophenol, sodium azide and MgCl, suggesting that an energized membrane and a mercapto group are essential and required for hydroxamate synthesis in Brudyrhizobium (lupin) strain WPBS 3201 D. 0 Elsevier, Paris Bradyrhizobium SQQ. / sideropbore 1iron deficiency R&mm6 - Production de sidkrophores par dessouches de Brudyrhizobium @pin) ayant pow& dansun milieu fer limitant. Six souches de Bradyrhizobium (lupin) ont et& Cvaluees pour leur capacite a produire, in vitro, des siderophores par des tests chimi- ques. Les souches WPBS 3201 D et WPBS 3211 D ont donne une reaction positive avec le CAS (chrome azurol S) et produisent des sidtrophores de type hydroxamate. Les quatre autres souches (USDA 3040, 3041, 3042 et CB 2272) ont donne en revanche des resultats negatifs quant 1 la production de sidtrophores. Le temps de generation, le rendement de croissance et la production d’hydroxamate de la souche WPBS 3201 D Ctaient affect& par la concentration en Fe dans le milieu de culture et par l’histoire de la culture. La production d’hydroxamate Ctait dependante de l’histoire des cellules en culture et notamment des conditions en concen- trations de Fe (0 et 20 pm01.L~‘) dans lesquelles elles avaient pousse. Les cellules ayant prealablement pousse avec 20 pmol.L-’ de Fe produisent une quantitk importante d’hydroxamate, contrairement aux cellules ayant pousse darts un milieu saris fer, lorsqu’elles sont reprises dans un milieu contenant jusqu’a 4 pmol.L-’ de fer. Elles Ctaient Cgalement plus sensibles a la repression par le fer que celles ayant pousse avec 5 pmol.L-’ On a montr6 que le mannitol est la meilleure source de carbone pour la production de sidero- phores. Enfin la synthese de siderophores est inhibe par l’acide 4-chloromercuribenzene sulfonique, le 2,4-dinitrophenol et le MgCl,, suggerant fortement qu’une Cnergie membranaire et un groupe mercapto sont essentiels pour la synthese d’hydroxamate chez les Bradyrhizobium (lupin) WPBS 3201 D. 0 Elsevier, Paris Bradyrhizobium SQQ. I sidkophore / di%cience en fer 1. INTRODUCTION Iron deficiency in nodulated legumes is very com- mon on alkaline soils, and affects such common agri- cultural crops as chick pea [21], French bean [ 131 and Eur. .I. Soil Bid.. I 16+5563/98/02/O Elsevw, Paris peanut [ 191. Although nodule intiation may occur nor- mally in peanut [ 191, it is drastically curtailed in lupins with iron deficiency [25]. There is, however, little evi- dence that iron deficiency in soil actually decreases the number of root nodule bacteria, implying either that