Iron acquisition during growth in an iron - deficient medium by Rhizobium sp . isolated f rom Cicer arietinum

Calcutta 700054, India 50 pM Fe3+. The siderophore was purified and characterized as containing 2,3dihydroxybenzoic acid (DHBA) as the core compound and threonine as i ts conjugate. The siderophore was able to reverse growth inhibition of the strain induced by ethylenediamine-di(o-hydroxyphenyl-acetic acid) (EDDA). A highaff ini ty iron-transport system capable of transporting 59Fe-siderophore complex was also induced in Rhizobium BlCC 651 grown under iron deficiency. Two protein bands of molecular masses 76 and 82 kDa were also inductively synthesized in the outer membrane of the cells. A partially purified ferrireductase enzyme of Rhizobium BlCC 651 catalysed reductive release of iron from the ferric chelate of DHBA. The enzyme had a Km of 0 3 mM for ferriDHBA, was constitutive in nature, and was present in the cytosolic fraction during growth under both iron-def icient and iron-suff icient conditions. The enzyme occurred as two isoenzymes with RF values of 048 and 051, respectively, in a nondenaturing polyacrylamide gel.