| Cultural conditions required for the induction of an adaptive acid-tolerance response (ATR) in Sinorhizobium meliloti and the question as to whether or not the ATR helps rhizobia improve their symbiosis with alfalfa at low pH. | |
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MedLine Citation:
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PMID: 19958387 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Sinorhizobium meliloti associates with Medicago and Melilotus species to develop nitrogen-fixing symbioses. The agricultural relevance of these associations, the worldwide distribution of acid soils, and the remarkable acid sensitivity of the microsymbiont have all stimulated research on the responses of the symbionts to acid environments. We show here that an adaptive acid-tolerance response (ATR) can be induced in S. meliloti, as shown previously for Sinorhizobium medicae, when the bacteria are grown in batch cultures at the slightly acid pH of 6.1. In marked contrast, no increased tolerance to hydrogen ions is obtained if rhizobia are grown in a chemostat under continuous cultivation at the same pH. The adaptive ATR appears as a complex process triggered by an increased hydrogen-ion concentration, but operative only if other--as yet unknown--concomitant factors that depend on the culture conditions are present (although not provided under continuous cultivation). Although the stability of the ATR and its influence on acid tolerance has been characterized in rhizobia, no data have been available on the effect of the adapted state on symbiosis. Coinoculation experiments showed that acid-adapted indicator rhizobia (ATR+) were present in >90% of the nodules when nodulation was performed at pH 5.6, representing a >30% increase in occupancy compared with a control test. We show that the ATR represents a clear advantage in competing for nodulation at low pH. It is not yet clear whether such an effect results from an improved performance in the acid environment during preinfection, an enhanced ability to initiate infections, or both conditions. The practical use of ATR+ rhizobia will depend on validation experiments with soil microcosms and on field testing, as well as on the possibility of preserving the physiology of ATR+ bacteria in inoculant formulations. |
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Authors:
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Walter O Draghi; Mar?a Florencia Del Papa; Mariano Pistorio; Mauricio Lozano; Mar?a de Los Angeles Giusti; Gonzalo A Torres Tejerizo; Edgardo Jofr?; Jos? Luis Boiardi; Antonio Lagares |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2009-11-06 |
Journal Detail:
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Title: FEMS microbiology letters Volume: 302 ISSN: 1574-6968 ISO Abbreviation: FEMS Microbiol. Lett. Publication Date: 2010 Jan |
Date Detail:
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Created Date: 2010-02-05 Completed Date: 2010-04-14 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7705721 Medline TA: FEMS Microbiol Lett Country: England |
Other Details:
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Languages: eng Pagination: 123-30 Citation Subset: IM |
Affiliation:
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IBBM - Instituto de Biotecnolog?a y Biolog?a Molecular, Departamento de Ciencias Biol?gicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT-CONICET-La Plata, Buenos Aires, Argentina. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Acids
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metabolism* Anti-Bacterial Agents / metabolism* Colony Count, Microbial Culture Media / chemistry Hydrogen-Ion Concentration Medicago sativa / microbiology* Microbial Viability* Plant Root Nodulation Sinorhizobium meliloti / metabolism, physiology* Stress, Physiological* Symbiosis* |
| Chemical | |
Reg. No./Substance:
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0/Acids; 0/Anti-Bacterial Agents; 0/Culture Media |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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