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. 1991 Feb;57(2):535–538. doi: 10.1128/aem.57.2.535-538.1991

Rapid In Situ Assay for Indoleacetic Acid Production by Bacteria Immobilized on a Nitrocellulose Membrane

John M Bric 1, Richard M Bostock 1,*, Sara E Silverstone 1,†
PMCID: PMC182744  PMID: 16348419

Abstract

We have developed a new assay that differentiates between indoleacetic acid (IAA)-producing and -nonproducing bacteria on a colony plate lift. Medium supplemented with 5 mM L-tryptophan is inoculated with isolates of interest, overlaid with a nitrocellulose membrane, and then incubated until bacterial colonies reach 1 to 2 mm in diameter. The membrane is removed to a filter paper saturated with Salkowski reagent and incubated until distinct red haloes form around the colonies. The colorimetric reaction to IAA is limited to a region immediately surrounding each colony, is specific to isolates producing IAA, occurs within 1 h after the membrane is placed in the reagent, and is sensitive to as little as 50 pmol of IAA in a 2-mm2 spot. We have used this assay for quantifying epiphytic and endophytic populations of IAA-producing isolates of Pseudomonas syringae subsp. savastanoi and for detecting IAA-producing colonies of other pseudomonads and Erwinia herbicola. The assay provides a rapid and convenient method to screen large numbers of bacteria.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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