DUGi

Factors affecting the distribution, abundance and diversity of uncultured archaeal groups in freshwater sediments

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@16021

Archaea are abundant in extreme environments but they are also a prevalent component of microbial communities in soils, marine or freshwater plankton and sediments. Many studies highlighted the prominent role of marine sedimentary Archaea in global nutrient cycles. Less information is available, however, on the diversity, abundance and ecological role of Archaea in freshwater sediments. A serious pitfall for the study of Archaea is their low cultivability under laboratory-controlled conditions thus constraining the progress towards the complete understanding of their metabolic capabilities and ecological functions. Most of the work is thus based on molecular techniques that allow the identification and quantification of target microorganisms without their cultivation. In this PhD project, we applied a combination of high-throughput sequencing and quantitative PCR to investigate the distribution, abundance and composition of archaeal communities in sediments from different freshwater systems (lakes, lagoons and reservoirs encompassing a wide range of conditions and typologies). The work has been focused in two archaeal groups consistently found, and especially abundant, in sediments: the phylum Bathyarchaeota and the class Thermoplasmata

Els arqueus abunden en ambients extrems per貌 tamb茅 s贸n un component rellevant dels s貌ls, del pl脿ncton oce脿nic i lacustre i dels sediments. Molts estudis han destacat la import脿ncia dels arqueus en els cicles de nutrients dels sediments marins tant a escala local com global. En canvi, es disposa de menys informaci贸 sobre la diversitat, abund脿ncia i paper que juguen els arqueus en sediments d鈥檃igua dol莽a a excepci贸 dels metan貌gens. Com a dificultat afegida, la majoria d鈥檃rqueus sedimentaris no s鈥檋an pogut cultivar encara al laboratori, el que dificulta el seu estudi. La soluci贸 a aquests problemes passa per l鈥檃plicaci贸 de t猫cniques moleculars que permeten la identificaci贸 i recompte dels microorganismes diana sense necessitat de cultivar-los. En aquesta tesi s鈥檋an combinat diferents t猫cniques moleculars (seq眉enciaci贸 massiva i PCR quantitativa) per a con猫ixer la distribuci贸, abund脿ncia i composici贸 de les comunitats d鈥檃rqueus en sediments de sistemes aqu脿tics d鈥檃igua dol莽a (llacs, llacunes i embassaments amb diferents condicions i tipologies). La tesi s鈥檋a centrat en dos grups d鈥檃rqueus que s贸n ubics i especialment abundants en sediments: el f铆lum Bathyarchaeota i la classe Thermoplasmata

Universitat de Girona