THE ROLE OF MICROBES IN METAL TRANSFORMATION

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THE ROLE OF MICROBES IN METAL TRANSFORMATION

• Irfan D. Prijambada

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METAL TRANSFORMATION
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CHARACTERS OF LOWER VALENCY METAL ION

• Soluble and stable
• Accumulated under reductive condition
• Readily oxidized into its higher valence metal ion

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CHARACTERS OF HIGHER VALENCY METAL ION

• Soluble at lower pH
• Insoluble at neutral and alkaline condition

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PROBLEMS REGARDING IONIC METAL

• Unavailability of metal ion under oxidative
  condition at neutral to alkaline pH (higher
  valence of metal ion insoluble at neutral to
  alkaline pH)
• Toxicity of metal ion under oxidative condition
  at acidic pH (higher valence of metal ion soluble
  at acidic pH)

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THE ROLE OF MICROBES IN SOLVING THE
UNAVAILABILITY OF METAL ION UNDER OXIDATIVE
CONDITION AT NEUTRAL TO ALKALINE PH

• Local acidulation by producing acid (lowering
  local pH)
• Local reduction of higher valence metal (lower
  valence metal soluble at any pH)
• Chelation by producing chelating agent
  (transporting metal ion into plant without
  changing their valence)

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LOCAL ACIDULATION BY PRODUCING ACID

• Done by any kind of microbes
• As intermediate products of microbes metabolism

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LOCAL REDUCTION OF HIGHER VALENCE METAL

• Done by many kind of microbes such as Bacillus,
  Pseudomonas, Proteus, Alcaligenes, Clostridia,
  and Enterobacteria
• Link to nitrate reduction system

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CHELATION OF HIGHER VALENCE METAL BY PRODUCING
CHELATING AGENT

• Chelating agents entrapped the insoluble higher
  valence metals
• Enterobacteria produce Enterobactin and
  Enterochelin (derivatives of Phenol-Catechol)
• Streptomyces and other bacteria produce
  Ferrioxamine (derivatives of Hydroxamic acids)
• Chelating agents have multiple hydroxyl or
  carbonyl groups

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THE ROLE OF MICROBES IN SOLVING THE TOXICITY OF
METAL ION UNDER OXIDATIVE CONDITION AT ACIDIC pH

• Producing carboxylic acids such as citric acid,
  malic acid, oxalacetic acid, succinic acid,
  lactic acid, and acetic acid
• Carboxylic acids have a chelating capability,
  increasing metal content of plant (which means
  increasing metal absorption by the plant) without
  harming them

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CHELATING CAPABILITY OF CARBOXYLIC ACIDS
Can be used to increase plant absorption of metal
(for bio and phytoremediating metal polluted land)
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ACCUMULATION OF LEAD IN THE ROOT OF DICOTYL
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ACCUMULATION OF LEAD IN THE ROOT OF MONOCOTYL
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ACCUMULATION OF LEAD IN THE ROOT OF WINTER
GRASSES AND SHRUBS
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ACCUMULATION OF LEAD IN THE ROOT OF SUMMER
GRASSES AND SHRUBS
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OTHER ROLE OF MICROBES IN REDUCING METAL
POLLUTION

• Absorbing metal ion by utilizing functional
  groups exist in the cell wall

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STRONG-WEAK ANION-CATHION INTERACTION (According
to Lewis)
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METAL ABSORPTION BY MICROBES

• Uranium is absorbed by the cells of Pseudomonas
  aeruginosa, Saccharomyces cerevisiae, Rhizopus
  arrhizus, and Aspergillus niger
• Thorium is absorbed by the cells of R. arrhizus,
  and A. niger
• Mercury is absorbed by the cells of S. cerevisiae

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METAL ABSORBING MICROBES

• Pseudomonas aeruginosa, Saccharomyces cerevisiae,
  Rhizopus arrhizus, and Aspergillus niger
• ALGAE Chlorella pyrenoidosa, C. vulgaris,
  Chaetoceros calcitrans, Stichococcus bacillaris,
  Chlamydomonas reinharti, Scenedesmus quadricauda,
  Ascopenyellum sp., and Sargassum sp.