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Title: Accumulation of the antibiotic phenazine-1-carboxylic acid in the rhizosphere of dryland cereals

Author
item MAVRODI, DMITRI - Washington State University
item MAVRODI, OLGA - Washington State University
item PAREJKO, JAMES - Washington State University
item BONSALL, ROBERT - Washington State University
item KWAK, YOUN-SIG - Washington State University
item Paulitz, Timothy
item Thomashow, Linda
item Weller, David

Submitted to: The ISME Journal: Multidisciplinary Journal of Microbial Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2010
Publication Date: 7/9/2010
Citation: Mavrodi, D.V., Mavrodi, O.V., Parejko, J.A., Bonsall, R.F., Kwak, Y., Paulitz, T.C., Thomashow, L.S., Weller, D.M. 2010. Accumulation of the antibiotic phenazine-1-carboxylic acid in the rhizosphere of dryland cereals. The ISME Journal: Multidisciplinary Journal of Microbial Ecology.

Interpretive Summary: Antibiotics produced by microorganisms in the environment are thought to function in microbial defense, fitness, competitiveness, biocontrol, communication and gene regulation. However, the frequency and amount of antibiotics produced in nature are poorly understood. In this study, we assessed the geographic distribution of indigenous phenazine antibiotic-producing bacteria and the amounts of phenazine antibiotics they produced on the roots of wheat grown in the low-rainfall zone of the Columbia Plateau, USA, and in nearby higher rainfall areas. The survey covered over 80 dryland fields situated within an area of about 5,436,318 acres. Antibiotic-producing bacteria were detected in all sampled fields, with average population sizes ranging from two thousand to ten million cells per gram fresh weight of root. Phenazine antibiotics were detected on the roots of plants from 20 of 21 fields sampled. The amounts of antibiotic recovered from roots were greater on roots with greater numbers of bacteria present.

Technical Abstract: Natural antibiotics are thought to function in microbial defense, fitness, competitiveness, biocontrol, communication and gene regulation. However, the frequency and amount of antibiotics produced in nature are poorly understood. In this study, we assessed the geographic distribution of indigenous phenazine-producing (Phz+) Pseudomonas spp. and the amounts of phenazine-1-carboxylic acid (PCA) in the rhizosphere of wheat grown in the low-precipitation zone (<350 mm) of the Columbia Plateau, USA, and in adjacent higher precipitation areas. The survey covered over 80 dryland fields situated within an area of about 22,000 km2. Phz+ Pseudomonas spp. were detected in all sampled fields, with mean population sizes ranging from log 3.2 to log 7.1 g-1 fresh weight of root. PCA was detected in the rhizospheres of plants from 20 of 21 fields sampled. Linear regression analysis demonstrated a significant (P <0.0001) relationship between the population level of Phz+ isolates and PCA recovered from the plant rhizosphere.