Mechanisms of resistence to heavy -metal
Oxidation
bonded
Reduce
Interactio n
Increase
Adsorption
Acidificati on
Reduce the absorption
the heavy metal content in the microbial cells at a low level is maintained without causing toxic effects on cells.
Cyanobacteria
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Fungi
• Small mold, single-celled yeast and fruiting body of large-scale fungus.
• Their cell walls contain consists largely of chitin and glucan.
Mode of resistance to heavy- metal
• Release of chelating agent and iron carrier.
• Acidification of the soil environment, • Change the REDOX potential. • Reduce the absorption. • Increase the discharge • Oxidation reduction
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Heavy –metal pollutants
Heavy metals being transferred to humans via the food chain would finally threaten human beings health.
Bioremediation on heavy metals
• Fungi have potential for heavy metal adsorption ability.
Saccharomyces Cerevisiae
White-rot fungi adsorbe Pb2 + ,the
highest removal rate can reach 95%.
algae, and the protozoa. • Alternate relationship between them and
plant. • Plant roots interaction and promote each
other.
Bacteria
• Widely distributed, many varieties, fast metabolism and reproduction.
Black rhizopus adsorbe Ag +, Pb2,
Li + and Cd2 +, Zn2 + and Ni2 +, Cu2 +, such as heavy metal ions.
Alage
• Wide distribution, a good biological adsorbent.
Metal resistance of microorganisms Plant rhizosphere bacteria Plant endophytic bacteria
Rhizosphere bacteria
• Grow in plant root system . • With bacteria, actinomycetes, fungi,
• The walls of algae has a larger surface area.
• Cell walls have a certain charge and viscous, these characteristics make the metal ion has the ability.
• Can enhance plant resistance to pathogens, drought, heavy metal.
• From Elsholtzia splendens and duck plantar grass (Commelina communis) .
• Firmicutes ,Actinobacteria, Proteobacteria.
• These bacteria strains in copper resistance of main groups .
The Cr6+ resistant plant growth promoting bacteria (PGPB), Pseudomonas sp. PsA4 and Bacillus sp. Ba32 were isolated from heavy metal contaminated soils and their plant growth promoting activity on the Indian mustard.
Scenedesmus Obliquus
• Has a larger adsorption capacity to UO22 +.
• The UO22 + concentration in the water from 5.0 mg/L fell to 0.05 mg/L.
Endophytic bacteria
• A kind of parasitic bacteria in plant body, all plants have endophytes.
• Endophytic bacteria (PGPB) is a kind of parasitic life, promote the growth of the host .
• Chemical composition of bacterial cell walls contain many heavy metal ions adsorption groups, such as carboxyl, amino, hydroxyl .
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