Insights into the Status of Heavy Metal Resistant Rhizobacterial …
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metals, which are less toxic, are released from the biosglutothionato complex into
the environment. More heavy metal is uptaken by Gram positive bacteria due to
presence of glycoproteins. Less heavy metal uptake by Gram negative bacteria is
observed due to phospholipids and Lipopolysaccharides (LPS) (Das et al. 2008).
Plant growth promoting rhizobacteria (PGPR) play a vital role in agriculture
mainly in the host plant adaptation to metal contaminated area by activation of
several physiological changes in the plant cell metabolism. This improves tolerance of growing plants towards high amount of heavy metal implications (Conrath
et al. 2006).The plant growth promoting bacteria assist the phytoremediation process
through mechanisms that support plant growth including nitrogen metabolisms,
synthesis and secretion of phytohormones such as indole-3-acetic acid (IAA),
Cytokinins, acetonin and 2,3 butanediol, and organic acids as well as defense
molecules such as siderophores, I—aminocyclopropane—I–carboxylate deaminase
(ACC) (Khan et al. 2009; Taghavi et al. 2009).
2 Various Methods for Removal of Heavy Metals
A variety of physical, chemical and biological methods were in use to remove metals
from the environment which are as follows (Joo et al. 2010; Pagnanelli et al. 2010):
2.1 Physical Methods
Reverse osmosis, Membrane technology, Evaporation recovery, Filtration and Ion
exchange.
2.2 Chemical Methods
Electrochemical treatment, chemical precipitation and oxidation/reduction reactions.
Though the above mentioned methods were not the initial choice as they are costly,
ineffective, and labor-intensive or the treatment process lacks selectivity (Chen 2008;
Tang 2008), the study carried out by Talos 2009, on bioremediation or biosorption—
based remediation techniques concluded that the natural processes are found to be
cost effective and in that line biological methods to remove heavy metals stands first
and employs microorganisms such as bacteria, fungi and algae. The present chapter
describes the types of heavy metals, chances of environmental release and its effect
on earth and life forms. In addition it specially emphasizes the role of Bacteria and
Rhizobacterial communities on heavy metal removal and detoxification and safe
release into the environment.
15
metals, which are less toxic, are released from the biosglutothionato complex into
the environment. More heavy metal is uptaken by Gram positive bacteria due to
presence of glycoproteins. Less heavy metal uptake by Gram negative bacteria is
observed due to phospholipids and Lipopolysaccharides (LPS) (Das et al. 2008).
Plant growth promoting rhizobacteria (PGPR) play a vital role in agriculture
mainly in the host plant adaptation to metal contaminated area by activation of
several physiological changes in the plant cell metabolism. This improves tolerance of growing plants towards high amount of heavy metal implications (Conrath
et al. 2006).The plant growth promoting bacteria assist the phytoremediation process
through mechanisms that support plant growth including nitrogen metabolisms,
synthesis and secretion of phytohormones such as indole-3-acetic acid (IAA),
Cytokinins, acetonin and 2,3 butanediol, and organic acids as well as defense
molecules such as siderophores, I—aminocyclopropane—I–carboxylate deaminase
(ACC) (Khan et al. 2009; Taghavi et al. 2009).
2 Various Methods for Removal of Heavy Metals
A variety of physical, chemical and biological methods were in use to remove metals
from the environment which are as follows (Joo et al. 2010; Pagnanelli et al. 2010):
2.1 Physical Methods
Reverse osmosis, Membrane technology, Evaporation recovery, Filtration and Ion
exchange.
2.2 Chemical Methods
Electrochemical treatment, chemical precipitation and oxidation/reduction reactions.
Though the above mentioned methods were not the initial choice as they are costly,
ineffective, and labor-intensive or the treatment process lacks selectivity (Chen 2008;
Tang 2008), the study carried out by Talos 2009, on bioremediation or biosorption—
based remediation techniques concluded that the natural processes are found to be
cost effective and in that line biological methods to remove heavy metals stands first
and employs microorganisms such as bacteria, fungi and algae. The present chapter
describes the types of heavy metals, chances of environmental release and its effect
on earth and life forms. In addition it specially emphasizes the role of Bacteria and
Rhizobacterial communities on heavy metal removal and detoxification and safe
release into the environment.