Microbial in-situ mitigation of arsenic contamination in plants and soils - In-Situ Remediation of Arsenic-Contaminated Sites - page 115

Table 6.3. Fungi investigated for environmental remediation of arsenic contamination.

Fungi Mechanism Reference

Ascomycota Tolerance, accumulation,

biosorption,
biovolatilization,
and removal

Srivastava et al . (2011), Su et al . (2010), Wysocki
and Tamas (2010), Adeyemi (2009), Cernansky et al .
(2009), Maheswari and Murugesan (2009), Vala et al .
(2010), Cernansky et al . (2007), Buckova et al . (2007),
Murugesan et al . (2006), Pokhrel and Viraragahavan
(2006), Canovas et al . (2003), Lehr et al . (2003),
Granchinho et al . (2002), Sharples et al . (2000),
Hofman et al . (2001), Visoottiviseth and Panviroj
(2001), Mukhopadhyay et al . (2000)

Basidiomycota Bioaccumulation Adeyemi (2009), Soeroes et al . (2005), Demirbas (2001),

Hofman et al . (2001), Lehr et al . (2003)

Glomeromycota Tolerance Xu et al . (2008)

Zygomycota Biosorption, tolerance and

bioaccumulation

Srivastava et al . (2011), Bai and Abraham (2003)

6.2.2 Role of soil
The toxicological effects of As depend upon its chemical form and bioavailability (La Force
et al ., 2000). The hydrated forms are considered to be the most toxic forms of As, and strong
complexes and species associated with colloidal particles are usually assumed to be less toxic
in soils (Russeva, 1995). The toxicity of As depends on various soil properties, for e.g., water
saturation/logging, pH redox conditions, other elements (phosphorus, silica and selenium), and
site hydrology. Plant and microbial components influence the adsorption capacity and behavior
of soil colloids (clay, metal oxides or hydroxides, calcium carbonate and/or organic matter)
and these effects may regulate solubility and bioavailability of As (Sadiq, 1997). In general, iron
oxides/hydroxides are most commonly involved in the adsorption of As in both acidic and alkaline
soils (Polemio et al ., 1982). As is known to adsorb to Fe/Mn oxyhydroxides, clays, carbonate
and organic matter (Dixit and Hering, 2003; Goldberg, 2002; Ongley et al ., 2007; Romero et al .,
2004). In soils contaminated by mining activities, As is primarily associated with amorphous iron
oxyhydroxides in soils (Ahumada et al ., 2004; Filippi et al ., 2004; Ghosh et al ., 2004). As can
also form secondary minerals, such as scorodite and sulfide minerals, or can co-precipitate with
other minerals (Fendorf et al ., 2004; Filippi et al ., 2004).

6.2.3 Role of microbes
As stated earlier, microorganisms play an important role in the environmental fate of As with
a multiplicity of mechanisms affecting transformations between soluble and insoluble As forms
and toxic and nontoxic As forms (Turpeinen et al ., 2002). Bacteria Pseudomonas arsenitoxi-
dans can derive metabolic energy from As(III) oxidation (Ilyaletdinov and Abdrashitova, 1981;
Anderson et al ., 2003), on the other hand, As(V) can be reduced by dissimilatory reduction
where microbes utilize As(V) as a terminal electron acceptor for anaerobic respiration. This has
been observed in several bacterial species including Sulfurospirillum barnesii, S. arsenophilum,
Desulfotomaculum auripigmentum, Bacillus arsenicoselenatis, B. selenitireducens, Crysigenes
arsenatis, Sphingomonas sp., Pseudomonas sp. and Wolinella sp. (Ahmann et al ., 1994; Lovley
and Coates, 1997; Macur et al ., 2001; Newman et al ., 1997; 1998; Stolz and Oremland, 1999;
Oremland et al ., 2000).
Microbes can impact As mobility through indirect natural processes such as oxidative sulfide
mineral dissolution, reduction of iron oxides, and sulfate reduction. Direct microbial processes