Adaptación de azoarcus sp. Cib a diferentes condiciones ambientales

Abstract

The genus Azoarcus harbors a high diversity of bacteria that have been classified in two different ecophysiological groups: on one hand, a group of bacteria that can live as plant endophytes and, on the other hand, a group of bacteria specialized in the anaerobic degradation of a wide range of aromatic compounds. In this thesis, we have used Azoarcus sp. CIB, a facultative anaerobe studied by its ability to degrade aromatic compounds anaerobically, as a model. For the first time, this work proves the ability to develop an endophytic lifestyle of an Azoarcus strain belonging to the specialized group of aromatic compounds degraders in anoxic conditions and its plant growth promotion properties has been characterized. Furthermore, the role of type IV pili, flagella and exopolysaccharide during plant colonization has been elucidated and its plant beneficial properties has been improved by the construction of a recombinant strain with ACC deaminase activity. A global transcriptomic approach in response to rice root extracts has been also carried out in order to understand the molecular mechanisms involved in the endophytic lifestyle and the role of the global regulator c-di-GMP during plant-endophyte interaction has been addressed. On the other hand, in this thesis has also been investigated the adaptation of Azoarcus sp. CIB to environmental conditions that have never been studied before and that confirms the high metabolic versatility of this strain. Thus, the resistance to some heavy metals (cadmium, nickel, zinc) and metalloids (selenite, tellurite, arsenate and arsenite) has been determined representing the first report about heavy metal and metalloid resistance in a strain of the genus Azoarcus. In this sense, the fact that selenite and tellurite resistance is couple to nanoparticles formation have also a great biotechnological interest. Finally, it has been demonstrated that Azoarcus sp. CIB is able to resist arsenate (ars genes) and to use arsenite as supplementary energy source, under anaerobic conditions, and the putative arx cluster, coding the anaerobic arsenite oxidase, has been characterized for the first time in a heterotrophic strain, being related with the use of arsenite as energy source and in arsenite resistance.