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Deconstructing the Soil Microbiome: Elucidating the Influence of Roots and Arbuscular Mycorrhizal Fungi on Soil Microbial Communities
Başlık:
Deconstructing the Soil Microbiome: Elucidating the Influence of Roots and Arbuscular Mycorrhizal Fungi on Soil Microbial Communities
Yazar:
Nuccio, Erin Elaine, author.
ISBN:
9780355989434
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (103 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Mary K. Firestone Committee members: Eoin Brodie; Steven Lindow; Ellen Simms.
Özet:
Soil is a complex medium that harbors vast amounts of microbial life. Plant roots interact with this immense body of microbial diversity in a multitude of ways, such as by acting as a host for mutualistic microorganisms, and by acting as a selective agent for soil microbial communities. These interactions in turn influence key processes in soil biogeochemical cycles, such as the decomposition of soil organic matter. In my dissertation research, I explored multiple facets of the plant-microbial system. In the first chapter, I examined how plant-associated mycorrhizal fungi influenced the decomposition of root detritus. In the second chapter, I investigated how roots act as selective agents for soil microbial communities, and determined how the selective pressure exerted by a root compares to other selective factors imposed by the soil-chemical environment and regional climate. In the final chapter, I examined how plant roots alter the microbial communities involved in the decomposition of root detritus in three domains of life: bacteria, archaea, and eukarya.
Arbuscular mycorrhizal fungi (AMF) are obligate symbionts that depend on their host plant for carbon nutrition, and are not known to directly decompose plant material. However, AMF commonly proliferate in organic material, and have been shown to stimulate decomposition in soil. In Chapter 1, I tested the hypotheses that AMF alter decomposition of root litter by: 1.) Influencing the composition of the saprotrophic microbial community, and 2.) Preferentially exporting nitrogen from the decomposing litter. A two-chamber microcosm system was employed to create a root-free soil environment and to control AMF access to 13C- and 15N- labeled root litter. Using a 16S rRNA gene microarray, I documented that approximately 10% of the bacterial community responded to the AMF, Glomus hoi. Phylogenetic analyses showed that the communities that responded to AMF were significantly clustered phylogenetically, which indicates that AMF may influence bacterial community assembly processes in decomposing litter. Nanometer-scale secondary ion mass spectrometry (NanoSIMS) was used to visualize the location of AMF-transported 13C- and 15N in plant roots. Bulk isotope-ratio mass spectrometry revealed that the AMF exported 4.9% of the litter-15N to the host plant (Plantago lanceolata L.), and litter-derived 15N was preferentially exported relative to litter-derived 13C. These results suggest that the AMF primarily took up N in the inorganic form, and N export is one mechanism by which AMF could modify the soil microbial community and decomposition processes.
The soil that immediately surrounds a root, referred to as the rhizosphere, form an ephemeral microhabitat that plays a crucial role in all vegetated ecosystems. As a root grows through soil, it interacts with the indigenous soil organisms and develops a microbiome that can facilitate the acquisition of nutrients by the plant, defend the plant from pathogens, and increase decomposition rates of organic material in the surrounding soil. Unraveling the factors that control how a root selects its rhizosphere microbial community is a key starting point for understanding the diversity of plant-microbial interactions that occur in soil. In Chapter 2, I examined how the selective influence of a root compares to other selective factors that shape the soil microbial community, such as soil characteristics and the regional climate. In addition, I recommend a procedure to improve the construction of phylogenetic trees from partial 16S sequences, such as those generated by Illumina and 454 sequencing. I identified the bacteria present in the soil immediately adjacent to the roots of wild oat, Avena sp., in three California grasslands using Illumina 16S rRNA gene sequencing. The rhizosphere communities were more influenced by factors related to regional effects (soil moisture, soil temperature, grassland of origin) than by local edaphic characteristics of the soil, while the background soil communities were more influenced by local chemical and pedological characteristics (pH, CEC, exchangeable cations, clay content). Avena selected for a root-specific microbiome that was strongly phylogenetically clustered. Even with a sequencing depth of approximately 70,000 sequences per sample, 17% of the taxa in the core root microbiome were not detected in the background soil. These results support the hypothesis that roots are agents of natural selection, which episodically maintain less abundant or rare populations in the soil microbial community.
Two-thirds of the carbon in the terrestrial biosphere is stored as stabilized soil organic matter, and this vast pool of carbon is derived primarily from decomposed plant material. The fluxes that control the size of this soil organic pool are critical to the global carbon cycle. Plant roots have been shown to increase the rate of soil organic matter decomposition, but the microbial and macrofaunal communities involved in this process are not well understood. (Abstract shortened by ProQuest.).
Notlar:
School code: 0028
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(677831.1) | 677831-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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