Caracterització de la comunitat de bacteris i arqueus oxidadors d’amoni a arrels de Typha angustifolia en diferents sistemes aquàtics

Abstract

The first step of nitrification, oxidation of ammonia to nitrite, is performed by both ammonia-oxidising archaea (AOA) and ammonia-oxidising bacteria (AOB). Oxidation of ammonia in water and sediments is highly dependent on the availability oxygen. Emergent macrophytes, such as Typha angustifolia, increase oxygen concentrations in the rhizoplane due to continuous oxygen leakage from roots, thus generating an aerobic microenvironment in close contact to the root surface The abundance, diversity and community structure of AOA and AOB were investigated, using amoA and 16S rRNA genes as a molecular biomarkers, to examine how oxygen permeability affect the spatial distribution of AOA and AOB on the root surface of Typha angustifolia, of three aquatic systems with different water conductivity. Massive sequencing and qPCR results showed that AOBs were the predominant ammonium oxidants in all three systems. The main AOB was Nitrosococcus and the main phylum of AOA was Thaumarchaeota. The relative abundances of the amoA gene in bacteria and archaea were significantly different in the three aquatic systems analysed. Likewise, comparisons of different aquatic systems with the 16S rRNA biomarker showed a heterogeneous distribution of the community. The different sections of the root (base, medium, tip, sediment) showed a homogeneous distribution of the microbial community but a significant difference of alpha-diversity. Overall, we were able to show that the communities of ammonium oxidizers linked to the roots of Typha angustifolia are mainly affected by the physicochemical conditions of the system, while the effect of oxygen diffusion at different parts of the root affects less