Banca de DEFESA: CECILIA DE SOUZA ANTONIO COTRIM

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : CECILIA DE SOUZA ANTONIO COTRIM
DATA : 27/02/2020
HORA: 09:00
LOCAL: Departamento de Solos, sala 24
TÍTULO:

Studies of organic sources of nitrogen in the growth and nitrogenase activity of five diazotrophic bacterial strains associated with sugarcane

PALAVRAS-CHAVES:

Biological nitrogen fixation. Root exudates. Amino acids.

PÁGINAS: 115
GRANDE ÁREA: Ciências Agrárias
ÁREA: Agronomia
SUBÁREA: Ciência do Solo
ESPECIALIDADE: Microbiologia e Bioquímica do Solo
RESUMO:

The interaction between host and bacteria can be affected by several factors, such as plant genotype, bacterial species/ strain and the environmental conditions, especially the available N source and form. Nitrogen-fixing bacteria isolated from sugarcane can be used as an inoculant that promotes plant growth and in addition, can act in the biological process of atmospheric N₂ fixation. But both the synthesis and the maintenance of the nitrogenase activity can be affected by the presence of nitrogen, both in the form of ammonium and nitrate ions, but also in the form of amino acids. The objective of this study was to evaluate the bacterial growth and nitrogenase activity of five strains / species of N-fixing bacteria in the presence of different sources of organic nitrogen. The studied strains were: Gluconacetobacter diazotrophicus strain BR11281, Herbaspirillum seropedicae BR11335, H. rubrisubalbicans BR11504, Paraburkholderia tropica BR11366 and Nitrospirillum amazonense BR11145. First, the growth of the strains was evaluated using the modified LGI medium changing 20% of the final volume to cane juice filter-sterilized. Then, using different minimal medium with the addition of glutamate and asparagine, in concentrations of 0.0, 0.1; 2.3 and 4.5 mg L^-1 and evaluating growth, final pH of the medium and nitrogenase activity. Simultaneously, two varieties of micropropagated sugarcane plants were grown in hydroponic solution for 35 days and the exudates were extracted to evaluate the composition in a CG-MS gas chromatograph. The objective was to detect changes in composition resulting from the inoculation of strains applied in mixture of five. The results showed that only BR11504 was not able to grow in the LGI-modified medium, with BR11281 having the longest generation time and BR11335 the shortest. Of the five strains, two showed acid growth, BR11281 and BR11366; and in less acidity medium, the strain BR11145. The results of adding glutamate to the LGI medium stimulated the growth of all strains, depending on the dose used. The acetylene-reducing activity, which indirectly measures nitrogenase activity, was reduced for the BR11335 strain at concentrations equal to or above 2.3 mg mL^-1, which is the most sensitive to the presence of this amino acid. Similarly, strain BR11366 reduced enzyme activity at concentrations above 2.3 mg mL^-1. The evaluations carried out with the aid of CG-MS in root exudates of the two varieties of sugarcane observed the presence of different fatty acids, as well as the carbohydrates such as fructose and sucrose, and in this case, the carbohydrates were detected only in the inoculated IACSP95-5000. Likewise, oxalic acid was detected in both varieties when inoculated as well. These results can help to understand the interaction of strains and varieties, producing substances that attract bacteria or even propitiate their multiplication in a different way. Different strains of diazotrophic bacteria, in the presence of amino acids such as glutamate and asparagine, showed differences in growth and nitrogenase activity depending on the strain and dose applied.

MEMBROS DA BANCA:
Presidente - 631.052.847-53 - VERONICA MASSENA REIS - UFRRJ
Interno - 681.282.827-00 - BRUNO JOSE RODRIGUES ALVES - EMBRAPA
Interno - 2626406 - LEANDRO AZEVEDO SANTOS
Externo à Instituição - GABRIELA CAVALCANTI ALVES - UFRRJ
Externo à Instituição - LUC FELICIANUS MARIE ROUWS - EMBRAPA