SYNTHESIS OF INDOLE-3-ACETIC-ACID BY THE SAPROPHYTIC PLANT-ASSOCIATEDBACTERIUM AGROBACTERIUM-RADIOBACTER

Peculiarities of indole-3-acetic acid (IAA) biosynthesis in saprophyti c plant-associated Agrobacterium radiobacter 5D-1 were studied. Synthe sis of IAA by this bacterium was found to be controlled by chromosomal genes; it was tryptophan-dependent and occurred, most likely, via the formation of indole-3-pyruvic acid, since it was inhibited by ammoniu m and glutamine and could not proceed when indole-3-acetamide was supp lied as a precursor instead of tryptophan. Mutants of strain 5D-1 with impaired IAA synthesis were isolated. Their culture liquid contained less IAA (30-40% of the IAA production by the parent strain) and unide ntified indole-containing compounds that exhibited an absorption maxim um at 485 nm staining in the Sal'kovskii reaction. These mutants can b e used for conclusive elucidation of the IAA biosynthesis pathway in A . radiobacter and mechanisms of its genetic control.