Eficiência simbiótica de estirpes de Cupriavidus necator tolerantes a zinco, cádmio, cobre e chumbo

Abstract

Resumo -O objetivo deste trabalho foi avaliar a tolerância de estirpes de Cupriavidus necator a zinco, cádmio, cobre e chumbo, além de determinar a eficiência simbiótica das estirpes mais tolerantes em associação a espécies leguminosas com potencial para revegetação. A tolerância foi testada em meio LB, suplementado com 2,5; 5,0; 7,5; 10; 12,5 . pudica e M. caesalpiniifolia e as estirpes UFLA01-659 e UFLA02-71, selecionadas na avaliação de eficiência simbiótica. A estirpe UFLA02-71 proporcionou incrementos de matéria seca da parte aérea de 870% em M. caesalpiniifolia, enquanto que UFLA01-659 proporcionou 885% em M. pudica e 924% em L. leucocephala. As estirpes UFLA01-659 e UFLA02-71, além da alta tolerância a metais pesados, apresentaram eficiência em fixar nitrogênio, em simbiose com essas leguminosas, em solos com rizóbios nativos capazes de nodulá-las, e devem ser avaliadas quanto ao seu potencial de utilização em programas de recuperação de áreas degradadas.Termos para indexação: áreas degradadas, β-proteobactéria, fixação biológica de nitrogênio, metais pesados, revegetação. Symbiotic efficiency of Cupriavidus necator strains tolerant to zinc, cadmium, copper and leadAbstract -The objective of this work was to evaluate the tolerance of Cupriavidus necator strains to zinc, cadmium, copper and lead, as well as to determine the symbiotic efficiency of the most tolerant ones in legume species suited for use in revegetation. Tolerance was evaluated in LB medium supplemented with 2.5, 5.0, 7.5, 10, 12.5 and 15 mmol L -1 of ZnSO 4 .7H 2 O, CdSO 4 .8H 2 O, CuSO 4 .5H 2 O and PbCl 2 , respectively, in comparison to a control without metal. The symbiotic efficiency of the four C. necator most metal-tolerant strains (UFLA02-71, UFLA02-73, UFLA01-659 and UFLA01-663) was determined, and these strains were inoculated in the species: Leucaena leucocephala, Enterolobium contortisiliquum, Acacia mangium, Mimosa caesalpiniifolia, M. pudica, M. pigra and M. acutistipula. Leucaena leucocephala, M. pudica and M. caesalpiniifolia and the strains UFLA02-71 and UFLA01-659, which presented the high symbiotic efficiency, were evaluated in pots with soil. UFLA02-71 provided increments of 870% in shoot dry matter of M. caesalpiniifolia, and UFLA01-659 provided 885% in M. pudica and 924% in L. leucocephala. These strains should be assessed for potential use in programs to restore degraded areas, since they showed high efficiency in nitrogen fixation and were competitive with indigenous rhizobia populations, besides being highly tolerant to heavy metals.Index terms: degraded areas, β-proteobacteria, biological nitrogen fixation, heavy metals, revegetation. IntroduçãoA recuperação das áreas degradadas pela atividade de mineração deve ser realizada para acelerar a sucessão natural. Com este propósito, a revegetação tem sido a principal prática para recompor e proteger o solo, evitar a poluição das águas e promover o retorno da biota edáfica. Para implantar a revegetação,

Tolerance to and Accumulation of Cadmium, Copper, and Zinc by Cupriavidus necator

“…In previous studies, the Cupriavidus necator strains UFLA 01-659, UFLA 01-663, and UFLA 02-71 (studied here), proved highly tolerant (2.5, 10, 10, and 5 mmol L -1 to Cd, Cu, Zn, and Pb, respectively) in solid medium, and reasonably efficient in biological N 2 fixation in symbiosis with the legume species Mimosa pudica, Mimosa caesalpiniifolia, and Leucaena leucocephala (Ferreira et al, 2012). In experiments with multicontaminated soil, strain UFLA 01-659 induced an increased of N content in shoots of Mimosa pudica and Leucaena leucocephala, and strain UFLA 02-71 in Mimosa caesalpiniifolia, contributing to soil recovery (Ferreira et al, 2013).…”

Novel Cupriavidus Strains Isolated from Root Nodules of Native Uruguayan Mimosa Species

“…of Cupriavidus as symbionts, other factors must be involved. One possibility is soil heavy metal content, since the copper-loving genus Cupriavidus is known for its tolerance to heavy metals, such as Cu, Zn, Pb, Cd, and Ni (50), and this includes some symbiotic Cupriavidus strains (28,79,80). Indeed, the very high heavy metal concentration in the soils in New Caledonia (NC) has been considered one of the factors responsible for the extended nodulation of the invasive M. pudica by C. taiwanensis, with many of the isolated strains being highly tolerant to Ni, Zn, and Cr (27).…”

Isolation, Characterization and Symbiotic Efficiency of Nitrogen-Fixing and Heavy Metal-Tolerant Bacteria from a Coalmine Wasteland

“…Bioremediation technologies are usually based on the biochemical and genetic capacity of microorganisms to interact and survive under adverse environmental conditions (Vázquez et al, 2006). Therefore, the introduction of plants in association with nitrogen-fixing bacteria constitutes a promising biotechnological tool for the recovery of problematic environments and degraded ecosystems (Chen et al, 2003;Wani et al, 2007;Ferreira et al, 2012).…”

“…Numerous studies have demonstrated the potential of nitrogen-fixing microorganisms isolated from copper, zinc, cadmium, lead, and arsenic mining areas to favor plant growth and enhance soil organic matter (Trannin et al, 2001;Matsuda et al, 2002;Carrasco et al, 2005;Zhan and Sun, 2011;Ferreira et al, 2012;Klonowska et al, 2012). Native nitrogenfixing bacteria in soils with high heavy metal contents and low pH are adapted to these stress types.…”