accumulate high levels of metal or pollutants. Cyanobacteria have rapid kinetics of
the metal removal and the possibility to treat water containing multiple metals.
Cyanobacteria as bioremediators have some advantages over other microorganisms because of their photoautotrophic nature and ability to fix atmospheric N 2
which makes them self-sufficient for growth and maintenance and adaptability to
survive in heavily polluted environments (Sokhoh et al. 1992). In addition, the
potentials of cyanobacteria in the removal of nutrients from wastewater rich in
nitrogenous and phosphorus compounds have been demonstrated. The ability to
remove nitrogenous and phosphate ions from wastewater was observed in
cyanobacteria such as Oscillatoria, Phormidium, Aphanocapsa, and Westiellopsis
(Blier et al. 1995; Pouliot et al. 1989). Cyanobacteria may be used for tertiary
treatment of urban and agro-industrial effluents and can help mitigate eutrophication
and metal toxicity problems in aquatic ecosystems. In natural environment, many
cyanobacteria form symbiotic associations with other aerobic or anaerobic microorganisms that showed degradation of hydrocarbons present in oil. In such type of
association, cyanobacteria are not directly responsible for the degradation of hydrocarbons and even facilitated the degradation process by providing oxygen and
nutrients to the associated oil-degrading bacteria (Abed et al. 2009).
Cyanobacteria are found in ponds, lakes, water streams, rivers, and wetlands.
They can easily survive the extreme environments such as hot springs, hyper-saline
waters, freezing environments, and arid deserts (Singh et al. 2013). Some of the
cyanobacterial strain shows potential metabolic adaptation in diverse habitats such
as in the highly saline condition (Reed and Stewart 1983). The ability of
cyanobacteria to survive extreme environmental conditions can be exploited for
better remediation of wastewater.
Cyanobacteria are characterized by the ability to oxidize oil components, pesticides, and complex organic compounds and accumulate metal ions, for example, Zn,
Co, and Cu (Mohapatra and Gupta 2005). Thus, cyanobacteria are promising tool for
the secondary treatment of urban, agricultural, or industrial effluents. Many of the
cyanobacteria synthesize metal-binding proteins “metallothioneins” that help organisms in the sequestration of toxic metal ions. The metal uptake was observed to be
dependent on various nutritional factors and the tolerance to the intracellular detoxification mechanism (Verma and Singh 1995).
Certain cyanobacteria produce bioflocculants that protect them from toxic effects
of heavy metals (Bender et al. 1994). Bioflocculants are extracellular macromolecules capable of clarifying turbid water and may remove dissolved nutrients and
heavy metals (Sharma et al. 2008) from water column thereby accelerating the
heterotrophic activity in the sediment region. Bioflocculants are characterized by
presence of numerous negatively charged binding sites that empowered the
cyanobacteria in removal of heavy metals from polluted sites. Bar-Or and Shilo
(1987) reported the production of bioflocculants by Phormidium sp. strain J-1
characterized by sulfated polysaccharides with attached fatty acids and proteins.
The uptake of metal ions (Cu, Pb, Zn, Ni, Cd, and Cr) in Spirulina platensis was
accompanied by liberation of protons suggesting an ion-exchange mechanism.
394
S. Mona et al.
the metal removal and the possibility to treat water containing multiple metals.
Cyanobacteria as bioremediators have some advantages over other microorganisms because of their photoautotrophic nature and ability to fix atmospheric N 2
which makes them self-sufficient for growth and maintenance and adaptability to
survive in heavily polluted environments (Sokhoh et al. 1992). In addition, the
potentials of cyanobacteria in the removal of nutrients from wastewater rich in
nitrogenous and phosphorus compounds have been demonstrated. The ability to
remove nitrogenous and phosphate ions from wastewater was observed in
cyanobacteria such as Oscillatoria, Phormidium, Aphanocapsa, and Westiellopsis
(Blier et al. 1995; Pouliot et al. 1989). Cyanobacteria may be used for tertiary
treatment of urban and agro-industrial effluents and can help mitigate eutrophication
and metal toxicity problems in aquatic ecosystems. In natural environment, many
cyanobacteria form symbiotic associations with other aerobic or anaerobic microorganisms that showed degradation of hydrocarbons present in oil. In such type of
association, cyanobacteria are not directly responsible for the degradation of hydrocarbons and even facilitated the degradation process by providing oxygen and
nutrients to the associated oil-degrading bacteria (Abed et al. 2009).
Cyanobacteria are found in ponds, lakes, water streams, rivers, and wetlands.
They can easily survive the extreme environments such as hot springs, hyper-saline
waters, freezing environments, and arid deserts (Singh et al. 2013). Some of the
cyanobacterial strain shows potential metabolic adaptation in diverse habitats such
as in the highly saline condition (Reed and Stewart 1983). The ability of
cyanobacteria to survive extreme environmental conditions can be exploited for
better remediation of wastewater.
Cyanobacteria are characterized by the ability to oxidize oil components, pesticides, and complex organic compounds and accumulate metal ions, for example, Zn,
Co, and Cu (Mohapatra and Gupta 2005). Thus, cyanobacteria are promising tool for
the secondary treatment of urban, agricultural, or industrial effluents. Many of the
cyanobacteria synthesize metal-binding proteins “metallothioneins” that help organisms in the sequestration of toxic metal ions. The metal uptake was observed to be
dependent on various nutritional factors and the tolerance to the intracellular detoxification mechanism (Verma and Singh 1995).
Certain cyanobacteria produce bioflocculants that protect them from toxic effects
of heavy metals (Bender et al. 1994). Bioflocculants are extracellular macromolecules capable of clarifying turbid water and may remove dissolved nutrients and
heavy metals (Sharma et al. 2008) from water column thereby accelerating the
heterotrophic activity in the sediment region. Bioflocculants are characterized by
presence of numerous negatively charged binding sites that empowered the
cyanobacteria in removal of heavy metals from polluted sites. Bar-Or and Shilo
(1987) reported the production of bioflocculants by Phormidium sp. strain J-1
characterized by sulfated polysaccharides with attached fatty acids and proteins.
The uptake of metal ions (Cu, Pb, Zn, Ni, Cd, and Cr) in Spirulina platensis was
accompanied by liberation of protons suggesting an ion-exchange mechanism.
394
S. Mona et al.