A Bacteria-Plant Model System to Study Nitrogen Fixation in Mangrove Ecosystems

  • Mangrove ecosystems are highly productive and rich in organic matter. However, they are considered low-nutrient environments, being nitrogen one of the main nutrients limiting mangrove growth. Nitrogen-fixing bacteria are one of the main inputs of nitrogen to these forests. High nitrogen fixation rates have been detected in mangrove sediments and roots. Moreover, studies indicated that the relationship between diazotrophs and mangroves might be mutualistic. Several diazotrophs from mangrove roots and the associated rhizosphere have been isolated or identify by phylogenetic studies of the nitrogenase-coding nifH gene. However, our knowledge about the molecular signals and cellular mechanisms that govern diazotroph-mangrove interactions is scarce. Thus, in this thesis a diazotroph-mangrove model system was established to better understand the importance of this interaction for the ecosystem and how environmental changes could impact this organismal interplay. For this, nitrogen-fixing bacteria were isolated from mangrove roots. Moreover, root colonization pattern of the selected nitrogen fixer and the impact of some of the environmental factors that could affect its nitrogen fixation were investigated. The first result showed that the diazotroph M. mangrovicola Gal22 was a prominent candidate for the establishment of the model system. This bacterium was shown to possess all features and requirements needed for being a representative model organism. Thus a detail phenotypic and genotypic characterization of strain Gal22 was conducted. A strong mangrove root colonization was observed by M. mangrovicola in the absence of carbon and nitrogen sources, suggesting that root exudates were instrumental in establishing the interaction. Nitrogen fixation by this diazotroph was increased in the presence of the roots, supporting the above results. Finally, changes in environmental factors such as temperature and salinity had a rather minor impact on nitrogen fixation by M. mangrov

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Publishing Institution:IRC-Library, Information Resource Center der Jacobs University Bremen
Granting Institution:Jacobs Univ.
Author:Maria Gabriela Alfaro Espinoza
Referee:Matthias Ullrich, Frank Oliver Glöckner, Jens Harder, Tim Jennerjahn
Advisor:Matthias Ullrich
Persistent Identifier (URN):urn:nbn:de:gbv:579-opus-1002142
Document Type:PhD Thesis
Date of Successful Oral Defense:2014/11/25
Year of Completion:2014
Date of First Publication:2015/01/30
PhD Degree:Marine Microbiology
School:SES School of Engineering and Science
Other Organisations Involved:Max-Planck-Institut für Marine Mikrobiologie (marmic)
Library of Congress Classification:Q Science / QK Botany / QK900-989 Plant ecology / QK930-938 Physiographic regions (General) / QK936-938 Land / QK938 Other special, A-Z / QK938.M27 Mangrove forests and swamps
Call No:Thesis 2014/43

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