Bacterias de vida libre fijadoras de nitrogeno atmosferico en rizosfera de frijol contaminada con queroseno | Nitrogen-fixing free-living bacteria in bean rhizosphere polluted with kerosene
2003
Hernandez A., E. | Ferrera-Cerrato, R. | Rodriguez V., R.
There are only few reports on free-living bacteria population in soils polluted by fuels like kerosene. At present, it is unknown whether the presence of hydrocarbon affects the activity of this group of soil microorganisms, and consequently, the incorporation of atmospheric nitrogen to the soil. In the present research, the effect of kerosene on the N fixing ability by this bacterial group, including free-living (FLB) and free-living hydrocarbonoclast bacteria (FLHB) in Phaseolus vulgaris L. was evaluated. Two factors were considered: presence of plant (with and without plant) and four concentrations of kerosene (0, 500, 2500, and 5000 mg kg(-1)). In greenhouse, the experiment involved eight treatments completely randomized with six replications. Roots and soils were sampled 19, 47, and 83 days after transplanting to evaluate the populations in the rhizoplane, rhizosphere and soil without plant. The acetylene reduction of FLHB was also evaluated in order to have an estimation of the possible atmospheric N fixation. The presence of kerosene did not dramatically affect either the growth of FLB and FLHB or the atmospheric nitrogen fixation. The highest population of FLB, 410 x 10(4) CFU g(-1) root, was present in the rhizoplane with 2500 mg kg(-1) of kerosene, while the highest population of FLHB, 299 x 10(4) CFU g(-1) soil, was recorded in the rhizosphere, with 500 mg kg(-1) kerosene. Twenty-one FLHB strains were isolated and 29% of the isolates showed nitrogenase enzyme activity. These results show that FLHB could be an option for the bioremediation of polluted soils by kerosene and induce the incorporation of N in the soil.
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