title: Brown algae overproduce cell wall polysaccharides as a protection mechanism against the heavy metal toxicity.
abstract: Brown algae are often used as heavy metal biomonitors and biosorbents because they can accumulate high concentrations of metals. Cation-exchange performed by cell wall polysaccharides is pointed out as the main chemical mechanism for the metal sequestration. Here, we biochemically investigated if the brown alga Padina gymnospora living in a heavy metal contaminated area would modify their polysaccharidic content. We exposed non-living biomass to Cd and Pb and studied the metals adsorption and localization. We found that raw dried polysaccharides, sulfate groups, uronic acids, fucose, mannose, and galactose were significantly higher in contaminated algae compared with the control ones. Metal concentrations adsorbed by non-living biomass were rising comparatively to the tested concentrations. Electron microscopy showed numerous granules in the cell walls and X-ray microanalysis revealed Cd as the main element. We concluded that P. gymnospora overproduces cell wall polysaccharides when exposed to high metal concentrations as a defense mechanism.
authors.affiliation: Laboratório de Biomineralização, Instituto de Ciências Biomédicas, CCS, Universidade Federal do Rio de Janeiro, Cidade Universitária, 21941-590 Rio de Janeiro, RJ, Brazil. andrade@histo.ufrj.br
authors.forename: Leonardo R
authors.initials: LR
authors.lastname: Andrade
authors.forename: Raquel N
authors.initials: RN
authors.lastname: Leal
authors.forename: Miguel
authors.initials: M
authors.lastname: Noseda
authors.forename: Maria Eugenia R
authors.initials: ME
authors.lastname: Duarte
authors.forename: Mariana S
authors.initials: MS
authors.lastname: Pereira
authors.forename: Paulo A S
authors.initials: PA
authors.lastname: Mourão
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
authors.forename: Gilberto M
authors.initials: GM
authors.lastname: Amado Filho
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D007854:Lead / Q000633:toxicity*; D000459:Phaeophyceae / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D011134:Polysaccharides / Q000096:biosynthesis*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D011134:Polysaccharides; D014874:Water Pollutants, Chemical; D002104:Cadmium; D007854:Lead