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Isolation of brazilian amazon cyanobacteria and further characterization for metal tolerance

Marli de Fatima Fiore J T Trevors; H Lee

2000

Localização: CENA - Cent. En. Nuclear na Agricultura    ((043) F518i 10096 )(Acessar)

  • Título:
    Isolation of brazilian amazon cyanobacteria and further characterization for metal tolerance
  • Autor: Marli de Fatima Fiore
  • J T Trevors; H Lee
  • Assuntos: BIOLOGIA MOLECULAR VEGETAL
  • Notas: Tese (Doutorado)
  • Descrição: Five genera (15 species) of 'N IND.2'-fixing cyanobacteria were isolated (Anabaena, Nostoc, Calothrix, Cyfindrospermum md Fischerella) from, sediment samples of floodplain areas of Brazilian Amazon region. Species of Nostoc and Fischerella were the most commonly isolated genera throughout the region. After purification of several strains and evaluation of colony-forming units and plating efficiency, five strains (Nostoc CENA-1 8, Nostoc CENA-21, Nostoc CENA-61, Fischerella CENA-19 and Cylindrospermum CENA-33) were selected for additional research. The growth curve based on chorophyll a measurement was determinated for these five strains and their ultrastructure analyzed by transmission electron microscopy continua... ) The effect of mercury, silver, cadmium, and chromium on the growth and nitrogen fixation of these five strains was evaluated. In general, the order of metal toxicity was Hg>Ag>Cd>Cr for growth based on chlorophyll a contents and Hg>Ag>Cr>Cd for nitrogen fixation. The growth inhibition, was dependent on cyanobacteria strains, metal concentration and also exposure time to the metals. Nostoc CENA-61 presented the highest tolerance to all the metals tested followed by Fischerella CENA-19. Whole cells of Nostoc CENA-61, in the presence of silver or chromium, were analyzed by transmission electron microscopy and energy-dispersive X-ray spectroscopy showed that both metals formed precipitate around the cells. The type of precipitate formed by silver
    was influenced by the growth medium used while the chromium precipitate was not continua... ) The widespread distribution of cyanobacteria in freshwater environments makes them an ideal system for investigating the genetic mechanisms of tolerance and toxicity that are induced during exposure to metal. To investigate the presence of a prokaryotic metallothionein gene (smtA) gene in various strains of cyanobacteria, which may serve as defense mechanisms against metal ion toxicity, it was necessary extract DNA from different forms of cyanobacteria. A rapid DNA miniprep method for the isolation genomic DNA from the different cyanobacteria was developed. The method has the advantage of producing sufficient yields of purified DNA, in less than 2 h, for manipulations such as PCR, restriction digests and hybridization continua... ) The presence of smtA in 12 cyanobacterial strains was investigated by PCR using primers designed from smtA sequence from Synechococcus sp. PCC 7942 and by DNA hybridization using smtA of Synechococcus sp. PCC 7942 as the probe. No smtA gene was found in any of the strains studied. Since there are several others distinct types of metallothioneins (MTs), these strains may present: MT sequences sufficiently different from smtA, that it was not possible to detect this gene homologue by PCR or genomic hybridizations. Efforts to detect MT gene homologues in cyanobacteria should be continued since it may offer an important monitoring tool for
    metal pollution in the freshwater environment
  • Data de criação/publicação: 2000
  • Formato: 260p. : il.
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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