Hydroxamate siderophores of endophytic bacteria Gluconacetobacter diazotrophicus isolated from sugarcane roots.

Isolates of Gluconacetobacter diazotrophicus (L1, L2, L3, L4, L5, L6, L7, L8 and L9) from sugarcane roots and standard isolate of G. diazotrophicus PAL5 were tested for the siderophores 3 production. Methods like FeCl test, Chrome Azural S (CAS) plate assay, Hydroxamate test, Carboxylate test were used. In Ferric chloride test, all of the G. diazotrophicus isolates produced purple color, In Chrome Azural S (CAS) plate assay, the formation of bright zone with yellowish fluorescent color in the dark colored medium was well documented in G. diazotrophicus L5 followed by L3 and L7, light yellowish fluorescent color was produced by the remaining isolates. In Hydroxamate assay, G. diazotrophicus local isolate L5 and L3 recorded the highest value when compared to the other local isolates and standard isolate G. diazotrophicus PAL5. Neither of the isolates recorded positive for Carboxylate test which means the isolates does not produce carboxylate type of siderophores. Experiments for type of siderophores revealed that G. diazotrophicus local isolate L5 produced higher amount of salicylate and catecholate type siderophores when compared to the other isolates.