was used in the past for the treatment of trypanosomiasis (Nash 1960), syphilis
(Moore 1933), topical eosinophilia (Maegraith 1966), psoriasis, verruca planum, and
Lichen planus (Goodman and Gilman 1942). Human interventions in the use of
arsenic in the form of weedicides, insecticides, and rodenticides for their agricultural,
industrial, and domestic purposes are getting reduced because of the replacement by
pesticides with low toxicity (Chisholm 1970). Arsenic-contaminated beer could
eventually lead to hepatic cirrhosis and chronic hepatitis (Reynold 1901; Wolf
1974). Thus, human activities with As-contaminated potable water have exposed
us to As toxicity (Nordstrom 2002) through farming systems including As-based
pesticides irrigation, fertilization, mining operations, and geochemical processes
(Meharg et al. 2009; Smedley and Kinniburgh 2002).
4 Arsenic Translocation From Soil to Plant
It is a universal accord that As is not prerequisite for plants, while the researches are
still out on whether or not it is a natural constituent of some plants. Conferring to
Gulz et al. (Gulz et al. 2005), a very acute concentration of As could play catalytic
effects in plants. The As concentration in plants is usually below 1.0 mg kg
À1 dry
weight (DW) (Adriano 2001). The accumulation of As by plants in the roots and its
translocation to shoots can occur either by active or passive transport system. It is
reported that As gets accumulated in plants on dry weight (<0.1%) basis in an
As-polluted soil (Austruy et al. 2013). Some monocots like paddy are known to
accumulate heavy metals in the grains (Sommella et al. 2013). Compared with US
and Chinese rice samples, As values from Spanish rice were estimated to be lower
(Carbonell-Barrachina et al. 2012). Numerous transporter proteins govern the As
translocation as the latter has a concentration gradient affinity between the farmers’
practice (source of soil or water) and the plant. Similarly, As concentrations in Italian
rice may vary from about 0.1 mg/kg grains to 0.3 mg/kg grains depending on the
sample site, variety, and region. Cadmium are usually lower and are detected at rates
between 0.01 and 0.1 mg/kg, and those for chromium values range from 0.1 mg/kg
to 1.0 mg/kg grains. Apart from being analogous to potassium (P), the As uses
numerous Pi channels to translocate inside a cell using a chemical gradient (Lei et al.
2012). In plants, the main constituents of P channels involved in As V uptake
(Nussaume et al. 2011; LeBlanc et al. 2013) are Pi transporter proteins (PHT)
which contain both low- and high-affinity P transports that are governed by PHT1
proteins. Nevertheless, these PHTs are involved in high-affinity transport and
low-affinity transport that are still unidentified. The unidirectional PHT1 proteins
may induce low-affinity activity in plants; thereby, plants uptake As III via numerous
bidirectional nodulin-26-like intrinsic proteins (NIPs), thus, allowing the As (III) to
translocate in both pumps depending on its gradient. In florae, As III is also stated to
use silicon (Si) transporters due to the analogy of Si and As (III); thus, deficiency in
Si increases the Si transporter (Lsi 1) influx in them. Being localized at epidermal
and endodermal cells, the transporters (Lsi1 and Lsi 2) govern the Si accumulation in
12 Arsenic-Transforming Bacteria: A Potential Weapon for Arsenic-Contaminated Soil
243
(Moore 1933), topical eosinophilia (Maegraith 1966), psoriasis, verruca planum, and
Lichen planus (Goodman and Gilman 1942). Human interventions in the use of
arsenic in the form of weedicides, insecticides, and rodenticides for their agricultural,
industrial, and domestic purposes are getting reduced because of the replacement by
pesticides with low toxicity (Chisholm 1970). Arsenic-contaminated beer could
eventually lead to hepatic cirrhosis and chronic hepatitis (Reynold 1901; Wolf
1974). Thus, human activities with As-contaminated potable water have exposed
us to As toxicity (Nordstrom 2002) through farming systems including As-based
pesticides irrigation, fertilization, mining operations, and geochemical processes
(Meharg et al. 2009; Smedley and Kinniburgh 2002).
4 Arsenic Translocation From Soil to Plant
It is a universal accord that As is not prerequisite for plants, while the researches are
still out on whether or not it is a natural constituent of some plants. Conferring to
Gulz et al. (Gulz et al. 2005), a very acute concentration of As could play catalytic
effects in plants. The As concentration in plants is usually below 1.0 mg kg
À1 dry
weight (DW) (Adriano 2001). The accumulation of As by plants in the roots and its
translocation to shoots can occur either by active or passive transport system. It is
reported that As gets accumulated in plants on dry weight (<0.1%) basis in an
As-polluted soil (Austruy et al. 2013). Some monocots like paddy are known to
accumulate heavy metals in the grains (Sommella et al. 2013). Compared with US
and Chinese rice samples, As values from Spanish rice were estimated to be lower
(Carbonell-Barrachina et al. 2012). Numerous transporter proteins govern the As
translocation as the latter has a concentration gradient affinity between the farmers’
practice (source of soil or water) and the plant. Similarly, As concentrations in Italian
rice may vary from about 0.1 mg/kg grains to 0.3 mg/kg grains depending on the
sample site, variety, and region. Cadmium are usually lower and are detected at rates
between 0.01 and 0.1 mg/kg, and those for chromium values range from 0.1 mg/kg
to 1.0 mg/kg grains. Apart from being analogous to potassium (P), the As uses
numerous Pi channels to translocate inside a cell using a chemical gradient (Lei et al.
2012). In plants, the main constituents of P channels involved in As V uptake
(Nussaume et al. 2011; LeBlanc et al. 2013) are Pi transporter proteins (PHT)
which contain both low- and high-affinity P transports that are governed by PHT1
proteins. Nevertheless, these PHTs are involved in high-affinity transport and
low-affinity transport that are still unidentified. The unidirectional PHT1 proteins
may induce low-affinity activity in plants; thereby, plants uptake As III via numerous
bidirectional nodulin-26-like intrinsic proteins (NIPs), thus, allowing the As (III) to
translocate in both pumps depending on its gradient. In florae, As III is also stated to
use silicon (Si) transporters due to the analogy of Si and As (III); thus, deficiency in
Si increases the Si transporter (Lsi 1) influx in them. Being localized at epidermal
and endodermal cells, the transporters (Lsi1 and Lsi 2) govern the Si accumulation in
12 Arsenic-Transforming Bacteria: A Potential Weapon for Arsenic-Contaminated Soil
243