Rapid in situ assay for indoleacetic acid production by bacteria immobilized on a nitrocellulose membrane

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 bacteri...

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Bibliographic Details
Published in:Applied and Environmental Microbiology 1991-02, Vol.57 (2), p.535-538
Main Authors: Bric, J.M. (University of California, Davis, CA), Bostock, R.M, Silverstone, S.E
Format: Article
Language:English
Subjects:
ACIDE INDOLACETIQUE
ACIDO INDOLACETICO
AGROBACTERIUM TUMEFACIENS
Biological and medical sciences
ERWINIA
ESSAI
Fundamental and applied biological sciences. Psychology
immobilized cells
indoleacetic acid
membranes
Microbiology
Microorganism-Plant Interactions
nitrocellulose
PRUEBAS
PSEUDOMONAS SYRINGAE
TECHNIQUE ANALYTIQUE
TECNICAS ANALITICAS
XANTHOMONAS CAMPESTRIS
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Summary: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
ISSN:0099-2240
1098-5336
DOI:10.1128/aem.57.2.535-538.1991