arsenic ions between the solid biosorbent and the liquid (aqueous) phase. This
process continues till establishment of equilibrium between the amount of
contaminant-bound biosorbent and the free ions in the solution. The extracellular
polymeric substances (EPSs) such as the peptidoglycan, phospholipids, lipopolysaccharides, proteins, teichoic and teichuronic acids of the bacterial cell, primarily
having a role in quorum sensing, play a key role in binding and adsorption of the
toxic arsenic ions. Several (carboxylic, amino, thiol, hydroxyl and hydrocarboxylic)
functional groups present in the biomass also actively participate in the binding
process (Mohapatra et al. 2017a, b).
Biochemistry of Bacterial Arsenic Removal
Studies have demonstrated that plant could sustain in high arsenic contaminated soils
when the phosphorus concentration was also high (Rosen et al. 2011). The arsenic in
soil and water occurring naturally generally enters the plant via phosphate transporters and facilitate bacterial survival under arsenic stress condition. A common
bacterial defence mechanism is the three detoxifying operons, ArsR, ArsC, and ArsB
(Musingarimi et al. 2010; Yang et al. 2012a, b). The transportation of arsenate to cell
and its reduction to arsenite is accomplished by ArsC gene and the outward
transportation of arsenite from cell by ArsB gene (Musingarimi et al. 2010).
Arsenic-tolerant bacteria Acinetobacter from the rhizospheric soil of Pteris
vittata, a fern, oxidises As
III , whereas a few others (Flavobacterium, Pseudomonas,
and Staphylococcus) could oxidise as well as reduce arsenic (Wang et al. 2012).
Agrobacterium radiobacter in the roots of Populus deltoids makes the plant tolerant
to 300 mg/kg Arsenic in soil, with a 54% removal efficiency (Wang et al. 2011).
Reports suggest volatilisation (Sphingomonas desiccabilis and Cyanobacteria),
adsorption (Ralstonia eutropha) and oxidation (Rhodococcus equi, Thiomonas
arsenivorans and Ensifer adhaerens) of arsenic from the contaminated soil
(Table 8.2; Liu et al. 2011; Mondal et al. 2008; Yin et al. 2011; Bag et al. 2010;
Dastidar and Wang 2012; Ito et al. 2012). A few of the siderophore-producing
arsenic-tolerant bacteria are Pseudomonas fluorescens, Micrococcus luteus and
Bacillus licheniformis. They are also active in solubilising phosphorus and fixing
nitrogen (Ivan et al. 2017). A genetically modified Rhizobium leguminosarum
incorporated with As
III S-adenosylmethionine methyltrasnferase gene (CrarsM)
from Chlamydomonas reinhardtii was useful in arsenic detoxification through the
methylation of As
III (Zhang et al. 2017). Some microbial mechanisms enhance the
plant growth by producing indole-3-acetic and other organic acids. These metabolites metabolise the heavy metal through the bacterial 1-ammino-cyclopropane-1carboxylic acid deaminase (Ma et al. 2011).
Algal Remediation
Algae from the groups Cyanophyta and Chlorophyta help in absorption and accumulation of arsenic from contaminated water (Mitra et al. 2017). The prokaryotic
8 Arsenic Contamination: Sources, Chemistry and Remediation Strategies
229
process continues till establishment of equilibrium between the amount of
contaminant-bound biosorbent and the free ions in the solution. The extracellular
polymeric substances (EPSs) such as the peptidoglycan, phospholipids, lipopolysaccharides, proteins, teichoic and teichuronic acids of the bacterial cell, primarily
having a role in quorum sensing, play a key role in binding and adsorption of the
toxic arsenic ions. Several (carboxylic, amino, thiol, hydroxyl and hydrocarboxylic)
functional groups present in the biomass also actively participate in the binding
process (Mohapatra et al. 2017a, b).
Biochemistry of Bacterial Arsenic Removal
Studies have demonstrated that plant could sustain in high arsenic contaminated soils
when the phosphorus concentration was also high (Rosen et al. 2011). The arsenic in
soil and water occurring naturally generally enters the plant via phosphate transporters and facilitate bacterial survival under arsenic stress condition. A common
bacterial defence mechanism is the three detoxifying operons, ArsR, ArsC, and ArsB
(Musingarimi et al. 2010; Yang et al. 2012a, b). The transportation of arsenate to cell
and its reduction to arsenite is accomplished by ArsC gene and the outward
transportation of arsenite from cell by ArsB gene (Musingarimi et al. 2010).
Arsenic-tolerant bacteria Acinetobacter from the rhizospheric soil of Pteris
vittata, a fern, oxidises As
III , whereas a few others (Flavobacterium, Pseudomonas,
and Staphylococcus) could oxidise as well as reduce arsenic (Wang et al. 2012).
Agrobacterium radiobacter in the roots of Populus deltoids makes the plant tolerant
to 300 mg/kg Arsenic in soil, with a 54% removal efficiency (Wang et al. 2011).
Reports suggest volatilisation (Sphingomonas desiccabilis and Cyanobacteria),
adsorption (Ralstonia eutropha) and oxidation (Rhodococcus equi, Thiomonas
arsenivorans and Ensifer adhaerens) of arsenic from the contaminated soil
(Table 8.2; Liu et al. 2011; Mondal et al. 2008; Yin et al. 2011; Bag et al. 2010;
Dastidar and Wang 2012; Ito et al. 2012). A few of the siderophore-producing
arsenic-tolerant bacteria are Pseudomonas fluorescens, Micrococcus luteus and
Bacillus licheniformis. They are also active in solubilising phosphorus and fixing
nitrogen (Ivan et al. 2017). A genetically modified Rhizobium leguminosarum
incorporated with As
III S-adenosylmethionine methyltrasnferase gene (CrarsM)
from Chlamydomonas reinhardtii was useful in arsenic detoxification through the
methylation of As
III (Zhang et al. 2017). Some microbial mechanisms enhance the
plant growth by producing indole-3-acetic and other organic acids. These metabolites metabolise the heavy metal through the bacterial 1-ammino-cyclopropane-1carboxylic acid deaminase (Ma et al. 2011).
Algal Remediation
Algae from the groups Cyanophyta and Chlorophyta help in absorption and accumulation of arsenic from contaminated water (Mitra et al. 2017). The prokaryotic
8 Arsenic Contamination: Sources, Chemistry and Remediation Strategies
229