Biotechnology for remediation and restoring the ecological status of soil in the places of permanent disposition of the troops by oil-destructor preparation on the basis of the microbial-plant association

The object of the study is a preparation of ecotoxicant destructor based on bacterial strains of Pseudomonas fluorescens, Pseudomonas putida, Pseudomonas délhiensis and associations of nodule bacteria Rhizobium loti with Lotus corniculatus. It is established, that during the simultaneous use of the bacteria and the legume Lotus corniculatus the rate of oxidation of petroleum hydrocarbons increases three times in comparison with the degradation rate of the pollutant after the separate use of each bacterial strain. We have received the preparation of ecotoxicant destructor – dry heterogeneous mass consisting of viable microbial cells of strains of P. delhiensis and R. lotus, seeds of leguminous plant Lotus corniculatus and delignified sawdust. Oil destructive activity of the preparation is proved in the course of microfield experiments. The degradation of ecotoxicants is proved by capillary gas chromatography-mass spectrometry with mass-selective detection. Bacteria of the strains, included in the preparation, are non-pathogenic for humans and animals, biocompatible, environmentally safe, stable, unpretentious to nutritional needs, technological, do not persist in environmental objects in the absence of a substrate for destruction. The technology of the production of the preparation is developed. The results of these studies demonstrate the possibility of practical use of the degradative potential of the preparation in the course of the implementation of the measures for soil reclamation, cleaning up ecotoxicants and restoring its ecological status.

Symbiotic effectiveness and ecological characterization of indigenous Rhizobium loti populations in Uruguay

The objectives of this work were to describe the distribution, density and seasonal variation of the indigenous populations of Rhizobium loti in different Uruguayan soils and to determine the symbiotic effectiveness and stress tolerance factors of different isolates, both with the aim of obtaining selected strains to re-introduce as inoculants in Lotus pastures. R. loti was present in ten soils studied and their densities varied from year to year and within each soil. All the isolates nodulated Lotus corniculatus effectively. The nodules in Lotus pedunculatus and Lotus subbiflorus were small, red on the surface and ineffective in nitrogen fixation. The study of 50 isolates from the ten soils showed high variability in their symbiotic efficiency and tolerance to pH. The indigenous population was acid tolerant in culture medium (pH 4.5), 83% of them could grow at pH 4.5 in 3 days. This work showed that there was a great diversity between the strains of R. loti isolated from Uruguayan soils and supports the importance of selecting among them the most efficient and resistant strains to be included in the inoculants.

Fixação do N2 em leucena (Leucaena leucocephala) em solo da região semi-árida brasileira submetido à salinização

Com a finalidade de avaliar a tolerância de rhizobium loti em Leucaena leucocephala cv K8, submetida a níveis crescentes de salinidade, realizou-se um experimento em casa de vegetação, usando-se um Podzólico Vermelho-Amarelo textura franco-arenosa, coletado em Serra Talhada (PE). O experimento obedeceu ao arranjo fatorial 5 x 4, no delineamento em blocos ao acaso, com 3 repetições. Foram usados 5 níveis de salinidade do solo (C.E. = 1,5; 6,6; 10,1; 12,8 e 14,4 dS m-1) e 2 tratamentos inoculados (NFB 494 e SEMIA 6069), fertilização nitrogenada com 200 mg kg-1 de N (NH4NO3), e o controle sem inoculação e sem adubação nitrogenada. O incremento dos níveis crescentes de salinidade reduziu a nodulação (número e massa de nódulos), o rendimento de matéria seca e a acumulação de N na parte aérea. O tratamento com fertilização nitrogenada inibiu totalmente a nodulação em leucena, em todos os níveis de salinidade; contudo, promoveu melhores rendimentos na acumulação de N e na produção de matéria seca. Observou-se resposta significativa das plantas inoculadas com a estirpe SEMIA 6069, em todas as características avaliadas, superando os resultados obtidos com o isolado NFB 494.