Lead toxicity in cyanobacterial porphyrin metabolism
The effect of Pb2+ on growth, tetrapyrrole photosynthetic pigment content, total free porphyrin, and 5-aminolevulinate dehydratase (ALA-D) activity of a cyanobacterium, Microchaete tenera, and its ability to sequester Pb2+ from the culture medium were studied. Pb2+ was assayed by graphite furnace at...
| Autores principales: | , |
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| Publicado: |
2001
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_15204081_v16_n1_p61_Zaccaro http://hdl.handle.net/20.500.12110/paper_15204081_v16_n1_p61_Zaccaro |
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| Sumario: | The effect of Pb2+ on growth, tetrapyrrole photosynthetic pigment content, total free porphyrin, and 5-aminolevulinate dehydratase (ALA-D) activity of a cyanobacterium, Microchaete tenera, and its ability to sequester Pb2+ from the culture medium were studied. Pb2+ was assayed by graphite furnace atomic absorption spectrophotometry. M. tenera growth and chlorophyll a content were not affected by 0.5, 1.0, and 6.0 ppm of Pb2+. These treatments doubled the protein content and increased the phycobiliprotein content by four times after 7 days. The ALA-D activity decreased in all concentrations by 63% at day 7 and by 34% at day 14. As a consequence of ALA-D inhibition, total free porphyrin also decreased by 64% at day 7 and by 40% at day 14. The highest biomass lead uptake (7454±565 μg Pb2+/g dry weight) was observed at day 3 with 6.0 ppm of Pb2+ in the culture medium. Uptake coefficient was highest (3723±279 μg Pb2+g-1 dry weight/ppm of applied Pb2+) with 1.0 ppm after 3 days. The increase in protein and antenna pigments on day 7 was probably a response to stress conditions and could explain why the toxic metal did not affect growth. ALA-D inhibition and high lead biomass content confirm the importance of this enzyme as a biological indicator for stress. © 2001 by John Wiley & Sons, Inc. |
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