The biological control bacterium Pseudomonas aureofaciens strain 30-84 produces three phenazine antibiotics. Phenazines are responsible for pathogen inhibition by strain 30-84 as well as its ability to persist in the rhizosphere. Although this bacterium can suppress take-all of wheat disease when applied as a seed inoculum, performance of this agent, as with many biological control agents, can be variable in the field. A factor in establishment and pathogen inhibition may be the indigenous microbial community that competes with strain 30-84 and may interfere with phenazine production as a competitive mechanism. In this study, a wheat rhizosphere microbial community library was screened and ca. 4% of the isolates were found to inhibit phenazine production by strain 30-84. A sub-group of these isolates was characterized and found to produce extracellular signals that suppressed phenazine gene expression. The signal from isolate PU-15 was initially characterized and appeared to be chemically and mechanistically unlike other known negative-acting signals. A genetic region was cloned from this isolate that decreased phenazine gene expression and production in strain 30-84. Negative communication also affected the ability of strain 30-84 to inhibit the pathogenic fungus Gaeuman-nomyces graminis pv. tritici in vitro. Therefore, negative communication may contribute to the inconsistencies of biological control in the field.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/278800 |
| Date | January 2002 |
| Creators | Morello, Joanne |
| Contributors | Pierson, Leland S., III |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Thesis-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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