Hong XiePasternak, J.J.Bernard R. Glick2014-09-022014-09-021996Current Microbiology Vol.32(1996) pp.67-71http://hdl.handle.net/123456789/5294Following transposon Tn5 mutagenesis of the plant growth-promoting rhizobacteTium Pseudomonas putida GR12-2, mutants that were able to grow in the presence of the tryptophan analog 5-fluorotryptophan were selected. Seven of the 50 5-fluorotryptophan-resistant mutants overproduced the phytohormone indoleacetic acid (IAA). Of these seven mutants, the highest level of IAA was observed with strain P. putida GR12-2/auxl,which produced four times the amount of indoleacetic acid synthesized by the wild-type strain. Strain P. putida GR12-2/auxl, in contrast to the wild type, lost the ability to stimulate the elongation of the roots of canola seedlings under gnotobiotic conditions. The growth rate, siderophore production, and 1-aminocyclopropane-1-carboxylate deaminase activity of mutant strain P. putida GR12-2/auxl were identical to those of the wild-type strain. The role of IAA in the mechanism of plant growth stimulation by P. putida GR12-2 and other plant growth-promoting rhizobacteria is discussed.enArticle