Publicação
Biofilm formation by Azospirillum brasilense: microbial socialization in the rhizosphere
| Resumo: | Azospirillum brasilense is a remarkable Plant-Growth Promoting Rhizobacteria (PGPR), with great potential as agricultural inoculant for several crops. Several isolates of this species have been produced as inoculant by some companies and applied in the agriculture as a biofertilizer. Therefore, there is a great interest in gathering more scientific knowledge that improves A. brasilense efficacy as a PGPR. To enhance the beneficial effects, from phytohormone synthesis to nitrogen fixation, it is essential that A. brasilense colonize plant roots and survive in the soil. For such, a vast array of traits is required, including biofilm formation and chemotactic response. The rhizosphere is a hotspot of biodiversity and a place of intensive networking; root exudates are the major plant tool to modulate the reciprocal interactions between the plant and the rhizosphere. In this work I focus on the influence of root symbiotic Arbuscular Mycorrhizal Fungi (AMF) and rhizospheric bacteria on A. brasilense biofilm formation with the following objectives: Firstly, to test if root exudates from maize plants colonized or not with different AMF species generate chemotactic response and stimulate biofilm formation of A. brasilense. Secondly, to test the interspecific influence of several soil bacterial strains in A. brasilense biofilm formation. Moreover, to assess the effect of Pseudomonas putida X236 and Bradyrhizobium japonicum by growing A. brasilense with supernatants, in co-inoculation, and with root exudates from maize plants inoculated with each one of those strains and with A. brasilense itself. Finally, inquire Phytohormone production, namely indol-3-acetic-acid (IAA), of A. brasilense in biofilm to assess a potential benefit to plants. Results showed that some mycorrhizal fungal species interact with A. brasilense via root exudates acting as chemoatractants. The soil borne bacteria P. putida X236 promoted biofilm formation of A. brasilense, indicating potential to create a co-inoculum with A. brasilense. Root exudates of maize plants inoculated with A. brasilense provoke a raise in its biofilm. IAA levels in biofilm cells were generally higher than in planktonic cells. This study highlights the importance of interspecific relations and of microbial consortia inoculums to maximize functions of the PGPR A. brasilense. |
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| Autores principais: | Cerqueira, Francisco Diogo de Almeida, 1990- |
| Assunto: | Biofilme Solos Biomassa Teses de mestrado - 2014 |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Azospirillum brasilense is a remarkable Plant-Growth Promoting Rhizobacteria (PGPR), with great potential as agricultural inoculant for several crops. Several isolates of this species have been produced as inoculant by some companies and applied in the agriculture as a biofertilizer. Therefore, there is a great interest in gathering more scientific knowledge that improves A. brasilense efficacy as a PGPR. To enhance the beneficial effects, from phytohormone synthesis to nitrogen fixation, it is essential that A. brasilense colonize plant roots and survive in the soil. For such, a vast array of traits is required, including biofilm formation and chemotactic response. The rhizosphere is a hotspot of biodiversity and a place of intensive networking; root exudates are the major plant tool to modulate the reciprocal interactions between the plant and the rhizosphere. In this work I focus on the influence of root symbiotic Arbuscular Mycorrhizal Fungi (AMF) and rhizospheric bacteria on A. brasilense biofilm formation with the following objectives: Firstly, to test if root exudates from maize plants colonized or not with different AMF species generate chemotactic response and stimulate biofilm formation of A. brasilense. Secondly, to test the interspecific influence of several soil bacterial strains in A. brasilense biofilm formation. Moreover, to assess the effect of Pseudomonas putida X236 and Bradyrhizobium japonicum by growing A. brasilense with supernatants, in co-inoculation, and with root exudates from maize plants inoculated with each one of those strains and with A. brasilense itself. Finally, inquire Phytohormone production, namely indol-3-acetic-acid (IAA), of A. brasilense in biofilm to assess a potential benefit to plants. Results showed that some mycorrhizal fungal species interact with A. brasilense via root exudates acting as chemoatractants. The soil borne bacteria P. putida X236 promoted biofilm formation of A. brasilense, indicating potential to create a co-inoculum with A. brasilense. Root exudates of maize plants inoculated with A. brasilense provoke a raise in its biofilm. IAA levels in biofilm cells were generally higher than in planktonic cells. This study highlights the importance of interspecific relations and of microbial consortia inoculums to maximize functions of the PGPR A. brasilense. |
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