||Roy, N.; Bhattacharyya, P.; Chakrabartty, P.K.
||Iron acquisition during growth in an iron-deficient
medium by Rhizobium sp. isolated from Cicer arietinum
||A catechol-type siderophore was produced extracellularly by Rhizobium sp. strain BlCC 651 isolated from Cicer arietinum during growth in iron-deficient medium. Production of the siderophore was fully repressed in the presence of Fe3+. The siderophore was purified and characterized as containing 2,3-dihydroxybenzoic acid (DHBA) as the core compound and threonine as its conjugate. The siderophore was able to reverse growth inhibition of the strain
induced by ethylenediamine-di(o-hydroxyphenyl-acetic acid) (EDDA). A high-affinity 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 ferri-DHBA, 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.