Arsenic distribution in environment and its bioremediation: A review

Microbial Redox Reaction

Table 2. Phytoremediation techniques (Vidali et al. , 2001)

Microbial mediated redox reactions mainly act

Technique

Plant mechanism

Surface medium

upon As (III) and As (V) species. Researchers

Uptake

and

have successfully isolated and characterized As

concentration of metal

via direct uptake into

Soils

resistant bacteria from different environmental

phytoextraction,

the plant tissue with

samples and concluded that these bacteria have

subsequent removal of

the capability to grow chemolithotrophically with

the plants

oxygen as an electron acceptor and As (III) as an

Plant

uptake

and

phytotrans-

Surface

water,

electron donor (Santini et al. , 2000; Duquesne et al. ,

degradation of organic

formation,

groundwater

compounds

2008). Furthermore, Ilyaletdinov and Abdrashitova

Soils,

(1981) concluded that bacteria derive metabolic

Root exudates cause

metal to precipitate

groundwater,

energy from As (III) oxidation. Strains of Bacillus

phytostabilization,

and

become

less

mine tailing

and Pseudomonas spp. (Frankenberger and Losi

available

1995) and Alcaligenes faecalis (Phillips and Taylor

Enhances

microbial

Soils,

1976) and Alcaligenes spp. (Osborne and Ehrlich

degradation in

groundwater,

1976) were found capable of oxidizing As (III) to

phytodegradation,

within

As(V). Gihiring et al. , (2001) explored the As (III) to

Rhizosphere

rhizosphere

As (V) oxidizing ability of Thermus aquaticus and

Uptake of metals into Surface water and

Rhizofiltration

Thermus thermophilus. Because As (V) is strongly

plant roots

water pumped

adsorbed onto inorganic soil components, microbial

Biovolatilization of As

oxidation could result in the immobilization of As.

Microbes are able to biomethylate inorganic As

On contrary, some strains use As (V) as a terminal

species to monomethylarsine and dimethylearsine

electron acceptor in an aerobic respiration, resulting

(Ridley et al. , 1977; Woolson 1977; Cullen and

in dissimilatory reduction of As (V) (Ahmann et

Reimer 1989; Gadd 1993). Due to their low boiling

al. , 1994; Stolz and Oremland 1999). Examples

point and/or high vapor pressure, these compounds

are: Sulfurospirillum barnesii, S. arsenophilum,

are susceptible for volatilization and could easily

Desulfotomaculum

auripigmentum,

Bacillus

be lost to the atmosphere (Braman and Foreback

Asoselenatis,

B.

selenitireducens,

Crysiogenes

1973). The conversion of As (V) to small amounts

arsenatis, Sphingomonas spp., Pseudomonas spp.

of volatile methylarsines was first described in a

and Wolinella spp. (Ahmann et al. , 1994; Lovley

pure culture of a methanogen, Methanobacterium

and Coates 1997; Newman et al. , 1998; Stolz and

bryantii (McBride et al. , 1971). Recently, several pure

cultures of anaerobes, including a methanogen

Oremland 1999). In addition, a plasmid-encoded,

( Methanobacterium

formicicum ), a fermentative

detoxifying reductase (arsC enzyme) present in the

bacterium ( Clostridium collagenovorans ) and sulfate-

cytoplasm of certain bacteria (e.g. Escherichia coli

reducing bacteria ( Desulfovibrio vulgaris and D.

and Staphylococcus aureus) reduces As (V) to As

gigas ), were also implicated in the formation of

(III) for its quick extrusion from the cell, resulting in

methylarsines (Michalke et al. , 2000. As (V) can be

As resistance (Ji et al. , 1994; Diorio et al. , 1995).

convertedtomonomethylarsineanddimmethylarsine

by Achromobacter sp. and Enterobacter sp.,

and to monomethylarsine, dimethylarsine and

trimethylarsine by Aeromonas spp. and Nocardia spp.

(Cullen and Reimer 1989).

197