Estudio metagenómico y culturómico de bacterias aisladas de phaseolus vulgaris y brassica napus, implicaciones funcionales y nutricionales de su aplicación como biofertilizantes en cultivos de interés agroalimentario y bioenergético, y evaluación del rol de la putrescina en la interacción bacteria-planta

  1. Jiménez Gómez, Alejandro
Supervised by:
  1. Paula García Fraile Director
  2. Raúl Rivas González Director

Defence university: Universidad de Salamanca

Fecha de defensa: 21 February 2020

  1. Pedro F. Mateos Chair
  2. Azahara Carmen Martin Ramirez Secretary
  3. Luis Sanz Andreu Committee member

Type: Thesis


Nowadays, the search for microorganisms capable to improve soil fertility and enhance plant nutrition and development is one of the research priorities according to new green policies. This is due to the negative environmental impacts from the massive use of fertilizers, which are currently essential components of modern agriculture system. One potential way to decrease the negative impacts resulting from continued use of chemical fertilizers is the inoculation with plant growth promoting rhizobacteria (PGPR). The general objective of this study is the evaluation and characterization of endophytic microorganisms of Phaseolus vulgaris and Brassica napus, analysing the potential of isolated strains to promote plant growth and improve the nutritional content of various crops with horticultural. Firstly, we have performed a metagenomic analysis of Phaseolus vulgaris nodules and, on the other hand, a metagenomic analysis of Brassica napus roots in order to obtain information about the general bacterial diversity and its potential interest. In order to isolate the potential strains, a culturomic study was the next step. We isolated 85 bacterial strains from surfaced-sterilized nodules and 112 bacterial strains from surfaced-sterilized rapeseed plant roots. In order to classify the bacterial biodiversity obtained, we divided the isolates in 125 different 879F-RAPD groups. The rRNA 16S sequence of one from each group was amplified, sequenced and compared with the sequences deposited in public databases. Several PGP in vitro mechanisms were evaluated according to the main objective of the present study. We tested the capability of our isolates to produce siderophores. Phosphate solubilization has been also analysed due to the importance of this element in plant nutrition and the problems caused by its deficit. Finally, we tested the capability of the isolates to synthesize cellulose, according to its described effects on root colonization and biofilm formation over the root surface. According to the results obtained in in vitro analysis of PGP traits, the strains Bacillus halotolerans SCCPVE07, Rhizobium laguerreae PEPV40 and Pseudomonas brassicacearum subsp. neurantiaca CDVBN10 were selected to deep in the study of their capability to promote plant growth and be potentially included in biofertilizer designs. One of the aims of this study was to analyse the effects of the three selected bacterial strains on the plant growth development in coriander and escarole under normal and saline conditions. Moreover, we also studied the effect of the inoculations on the phenolic composition and mineral content of these plants. Finally, an objective of this thesis was to build on existing knowledge in PGP bacterial-plant interactions under salinity stress. Thus, and after the analysis of the genome sequence of strain CDVBN10 and a deep revision of the available literature, we focused on polyamines. Plant polyamines are acknowledged regulators of plant growth, development and stress responses, they can act as reactive oxygen species (ROS) scavengers and activators of key antioxidant enzymes. Strain CDVBN10 has also a metabolic route to synthesize polyamines. One of the genes involved in the biosynthesis of polyamines is that encoding the n-carbamoyl putrescine amidase (cpa gene). This cpa gene is specifically involved in putrescine biosynthesis and all the other polyamines synthesized by P. brassicacearum CDVBN10 derive from the synthesis of putrescine. Therefore, we hypothesised that the interruption of this gene could have some effect in the capability of Pseudomonas brassicacearum subsp. neurantiaca CDVBN10 to promote the resistance of the plants to stress salinity.