Browsing by Author "Bernard R. Glick"

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    The enhancement of plant growth by free-living bacteria
    (1995) Bernard R. Glick
    The ways in which plant growth promoting rhizobacteria facilitate the growth of plants are considered and discussed. Both indirect and direct mechanisms of plant growth promotion are dealt with. The possibility of improving plant growth promoting rhizobacteria by specific genetic manipulation is critically examined.
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    Isolation and Characterization of Mutants of the Plant Growth-Promoting Rhizobacterium Pseudomonas putida GR12-2 That Overproduce Indoleacetic Acid
    (1996) Hong Xie; Pasternak, J.J.; Bernard R. Glick
    Following 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.
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    A novel procedure for rapid isolation of plant growth promoting pseudomonads
    (1995) Bernard R. Glick; Damir M. Karaturovic; Peter C. Newell
    A rapid and novel procedure for the isolation of plant growth promoting rhizobacteria (PGPR) is described. This method entails screening soil bacteria for the ability to utilize the compound 1-aminocyclopropane-l-carboxylate (ACC) as a sole N source, a trait that is a consequence of the presence of the activity of the enzyme ACC deaminase. This trait appears to be limited to soil bacteria that are also capable of stimulating plant growth. Seven different soil samples from two geographically disparate locations were found to contain pseudomonads that were able to to utilize ACC as a N source. Each of the seven strains was shown, by the ability of the bacterium to promote canola seedling root elongation under gnotobiotic conditions, to be a PGPR. The method described here may be used to replace the otherwise slow and tedious process of testing individual bacterial strains for their ability to promote plant growth, thereby significantly speeding up the process of finding new PGPR.