Plant growth promotion and fungicidal activity in a siderophore-producing strain of Proteus sp.

A proteus strain inhibited mycelial growth of Fusarium oxysporum in vitro. Seed bacterization showed significant plant growth promotion and Fusarium-wilt suppression activity of Phaseolus mungo in a gnotobiotic system. The culture filtrate of this strain exhibited three prominent bands in UV-VIS spectra between 300 and 400 nm. The growth promotion assay of the extracted compound against different indicator organisms indicated the production of a compound related to a 2-oxoacid-type siderophore. The HPLC of the purified ethyl acetate extract of the strains and standard 4-methyl-2-oxopentanoate (2-oxoisocaproate) revealed a single peak, similarly as the coinjection of the extract and the standard. The production of siderophore, probably 2-oxoisocaproate, was demonstrated.