solubilization. Klebsiella spp. significantly solubilized inorganic phosphate even in
the presence of recommended and high levels of pesticides (Ahemad and Khan
2011). Azotobacter phosphate solubility was detected at a maximum of 1% chlorpyrifos concentration and reduced to 35–40% at high concentration of chlorpyrifos
(Chennappa 2016).
2.4 Microorganisms Involved in Degradation of Pesticides
Pesticides are usually toxic and have a xenobiotic nature. When constantly exposed
to high concentrations of toxic and persistent pesticides, a wide range of soildwelling microorganisms, including bacteria and fungi, may develop the ability to
use pesticides as a source of energy and nutrients. Partial or complete mineralization/
conversion of such pesticides in the soil make them more or less non-toxic than the
parent molecule, leading to bioremediation of such contaminated areas (Alexander
1999). In most cases, high levels of pesticides increase bacterial and fungal
populations, where soil microorganisms utilize pesticides as a source of carbon,
energy, and other nutrients. For example, the pesticide diazinon and herbicide
linuron significantly increased the number of heterotrophic bacteria and fungi in
the soil after 28 days, when the concentration from 15 mg kg
À1 soil to 1500 mg kg
À1
soil was gradually increased (Cycon and Piotrowska-Seget 2007).
Due to environmental issues such as accumulation of pesticides in food and water
supply, biodegradation has been recognized as a safe, convenient, and economically
viable tool for the cleaning of pesticide-contaminated soils due to low cost, ease of
use, high efficiency, and no secondary pollution (Sindhu 2007; Ning et al. 2012;
Ramu and Seetharaman 2014; Ozdal et al. 2017). Most recalcitrant pesticides are
captivated into the soil and, therefore, are not properly accessible to bacteria due to
intracellular degradation processes. Among microbial species, bacteria, fungi, and
actinomycetes are main pesticide degraders (Table 2.2) have been isolated from soils
either by direct serial dilution method (Fig. 2.3) or by enrichment culture technique
using particular pesticides as substrate.
Several microorganisms that can mineralize organophosphates (OPs) have been
isolated, including bacteria such as Pseudomonas aeruginosa F10B (Das and Singh
2003), Ochrobactrum anthropi B2 (Qiu et al. 2006), Hyphomicrobium spp. MAP-1
(Wang et al. 2010a, b), Agrobacterium sp. Yw12 (Wang et al. 2012), and belonging
to Bacillus, Flavobacterium, Micrococcus, and Pseudomonas (Singh and Walker
2006), as well as fungi Penicillium oxalicum ZHJ6 (Zhao et al. 2010), Fusarium spp.
F1 (Zhao et al. 2009), Aspergillus sydowii PA F-2 (Tian et al. 2016), and Saccharomyces (Gao et al. 2011). Another pesticide monocrotophos (MCP) was degraded
by Pseudomonas aeruginosa F10B, and Clavibacter michiganense subsp insidiosum
SBL 11, which used MCP as a source of phosphorus (Das and Singh 2003; Singh
and Singh 2003). MCP can also be degraded by Bacillus megaterium (Bhadbhade
et al. 2002). Aspergillus sydowii PAF-2 has been reported to metabolize 75.31% OP
trichlorofon (100 mg L
À1 ) in 7 days (Tian et al. 2016). Salt-resistant actinomycete
2 Bioremediation of Pesticides: An Eco-Friendly Approach for Environment. . .
33
the presence of recommended and high levels of pesticides (Ahemad and Khan
2011). Azotobacter phosphate solubility was detected at a maximum of 1% chlorpyrifos concentration and reduced to 35–40% at high concentration of chlorpyrifos
(Chennappa 2016).
2.4 Microorganisms Involved in Degradation of Pesticides
Pesticides are usually toxic and have a xenobiotic nature. When constantly exposed
to high concentrations of toxic and persistent pesticides, a wide range of soildwelling microorganisms, including bacteria and fungi, may develop the ability to
use pesticides as a source of energy and nutrients. Partial or complete mineralization/
conversion of such pesticides in the soil make them more or less non-toxic than the
parent molecule, leading to bioremediation of such contaminated areas (Alexander
1999). In most cases, high levels of pesticides increase bacterial and fungal
populations, where soil microorganisms utilize pesticides as a source of carbon,
energy, and other nutrients. For example, the pesticide diazinon and herbicide
linuron significantly increased the number of heterotrophic bacteria and fungi in
the soil after 28 days, when the concentration from 15 mg kg
À1 soil to 1500 mg kg
À1
soil was gradually increased (Cycon and Piotrowska-Seget 2007).
Due to environmental issues such as accumulation of pesticides in food and water
supply, biodegradation has been recognized as a safe, convenient, and economically
viable tool for the cleaning of pesticide-contaminated soils due to low cost, ease of
use, high efficiency, and no secondary pollution (Sindhu 2007; Ning et al. 2012;
Ramu and Seetharaman 2014; Ozdal et al. 2017). Most recalcitrant pesticides are
captivated into the soil and, therefore, are not properly accessible to bacteria due to
intracellular degradation processes. Among microbial species, bacteria, fungi, and
actinomycetes are main pesticide degraders (Table 2.2) have been isolated from soils
either by direct serial dilution method (Fig. 2.3) or by enrichment culture technique
using particular pesticides as substrate.
Several microorganisms that can mineralize organophosphates (OPs) have been
isolated, including bacteria such as Pseudomonas aeruginosa F10B (Das and Singh
2003), Ochrobactrum anthropi B2 (Qiu et al. 2006), Hyphomicrobium spp. MAP-1
(Wang et al. 2010a, b), Agrobacterium sp. Yw12 (Wang et al. 2012), and belonging
to Bacillus, Flavobacterium, Micrococcus, and Pseudomonas (Singh and Walker
2006), as well as fungi Penicillium oxalicum ZHJ6 (Zhao et al. 2010), Fusarium spp.
F1 (Zhao et al. 2009), Aspergillus sydowii PA F-2 (Tian et al. 2016), and Saccharomyces (Gao et al. 2011). Another pesticide monocrotophos (MCP) was degraded
by Pseudomonas aeruginosa F10B, and Clavibacter michiganense subsp insidiosum
SBL 11, which used MCP as a source of phosphorus (Das and Singh 2003; Singh
and Singh 2003). MCP can also be degraded by Bacillus megaterium (Bhadbhade
et al. 2002). Aspergillus sydowii PAF-2 has been reported to metabolize 75.31% OP
trichlorofon (100 mg L
À1 ) in 7 days (Tian et al. 2016). Salt-resistant actinomycete
2 Bioremediation of Pesticides: An Eco-Friendly Approach for Environment. . .
33