5.3 Agrochemicals
5.3.1 Pesticides
Pesticides were widely used in agricultural ecosystem which include herbicide,
insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide,
insect repellent, animal repellent, antimicrobial and fungicide. These pesticides
were used in order to reduce the yield loss due to pest organisms. As the pest
organism gets resistance, the excessive usage of pesticides to protect crop plants
was encountered. In adverse, it has serious impact on farmers’ health, human on food
consumption, contamination of air, soil and water, non-target and beneficial organism and soil fertility (Aktar et al. 2009). In the current scenario, although the usage of
chemical pesticides was reduced and replaced with eco-friendly management tools,
the residues in the soil still remain without proper degradation (Gupta and Dikshit
2010). Application of cyanobacteria as bioremediation approach for contaminated
soil would reduce contaminant residues as well as improve soil fertility.
Cyanobacteria have the natural ability to degrade most of the pesticides, and
Kuritz and Wolk (1995) acknowledge that Anabaena sp. and Nostoc ellipsosporum
could naturally degrade lindane (g-hexachlorocyclohexane) and also studied that the
genetic engineering results in increased lindane degradation of these cyanobacteria.
In addition to lindane, engineered cyanobacteria were evidenced to degrade chlorinated pollutant 4-chlorobenzoate. Similarly, degradation of lindane residue by
Oscillatoria, Synechococcus, Nodularia, Nostoc, Anabaena, and Microcystis were
also reported (El-Bestawy et al. 2007). Detoxification of endosulfan pesticide by
Anabaena species were reported (Lee et al. 2003). Utilization of organophosphorus
pesticide malathion as phosphorous source was reported in Anabaena oryzae,
Nostoc muscorum and Spirulina platensis, which results in biodegradation of malathion. In the presence of malathion, a significant increase in biomass was also noted
in these cyanobacterial strains (Ibrahim et al. 2014). Anabaena sp. and Nostoc
sp. were able to detoxify the organophosphorus pesticide Fenamiphos through
hydrolysis and oxidation approach. Hydrolysis of Fenamiphos leads to stable
non-toxic products while oxidation gives the products which are toxic to aquatic
invertebrates (Cáceres et al. 2008).
Glyphosate is a common organic phosphorus herbicide used all over the world
and sold in the market name ‘Round-up’. Accumulation of glyphosate and its
degradation product aminomethylphosphonic acid (AMPA) in several environments
has been identified which results with consequences like emergence of antibioticresistant microorganisms and shift in microbial community composition of soil,
plants and animal guts (Van Bruggen et al. 2018). Basically, cyanobacteria grow
well in excess phosphorous condition in order to fix nitrogen and has the ability to
accumulate phosphorous. Cyanobacteria could break down glyphosate using alkaline phosphatase enzyme and utilize it for metabolism process, and the mechanism
has been studied in Nostoc sp. L. ACN 101 and Westiellopsis sp. L. ACW
101 (Balakumar and Ravi 2001). Tolerance to glyphosate was reported in
5 Cyanobacteria-Mediated Bioremediation of Problem Soils
143
5.3.1 Pesticides
Pesticides were widely used in agricultural ecosystem which include herbicide,
insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide,
insect repellent, animal repellent, antimicrobial and fungicide. These pesticides
were used in order to reduce the yield loss due to pest organisms. As the pest
organism gets resistance, the excessive usage of pesticides to protect crop plants
was encountered. In adverse, it has serious impact on farmers’ health, human on food
consumption, contamination of air, soil and water, non-target and beneficial organism and soil fertility (Aktar et al. 2009). In the current scenario, although the usage of
chemical pesticides was reduced and replaced with eco-friendly management tools,
the residues in the soil still remain without proper degradation (Gupta and Dikshit
2010). Application of cyanobacteria as bioremediation approach for contaminated
soil would reduce contaminant residues as well as improve soil fertility.
Cyanobacteria have the natural ability to degrade most of the pesticides, and
Kuritz and Wolk (1995) acknowledge that Anabaena sp. and Nostoc ellipsosporum
could naturally degrade lindane (g-hexachlorocyclohexane) and also studied that the
genetic engineering results in increased lindane degradation of these cyanobacteria.
In addition to lindane, engineered cyanobacteria were evidenced to degrade chlorinated pollutant 4-chlorobenzoate. Similarly, degradation of lindane residue by
Oscillatoria, Synechococcus, Nodularia, Nostoc, Anabaena, and Microcystis were
also reported (El-Bestawy et al. 2007). Detoxification of endosulfan pesticide by
Anabaena species were reported (Lee et al. 2003). Utilization of organophosphorus
pesticide malathion as phosphorous source was reported in Anabaena oryzae,
Nostoc muscorum and Spirulina platensis, which results in biodegradation of malathion. In the presence of malathion, a significant increase in biomass was also noted
in these cyanobacterial strains (Ibrahim et al. 2014). Anabaena sp. and Nostoc
sp. were able to detoxify the organophosphorus pesticide Fenamiphos through
hydrolysis and oxidation approach. Hydrolysis of Fenamiphos leads to stable
non-toxic products while oxidation gives the products which are toxic to aquatic
invertebrates (Cáceres et al. 2008).
Glyphosate is a common organic phosphorus herbicide used all over the world
and sold in the market name ‘Round-up’. Accumulation of glyphosate and its
degradation product aminomethylphosphonic acid (AMPA) in several environments
has been identified which results with consequences like emergence of antibioticresistant microorganisms and shift in microbial community composition of soil,
plants and animal guts (Van Bruggen et al. 2018). Basically, cyanobacteria grow
well in excess phosphorous condition in order to fix nitrogen and has the ability to
accumulate phosphorous. Cyanobacteria could break down glyphosate using alkaline phosphatase enzyme and utilize it for metabolism process, and the mechanism
has been studied in Nostoc sp. L. ACN 101 and Westiellopsis sp. L. ACW
101 (Balakumar and Ravi 2001). Tolerance to glyphosate was reported in
5 Cyanobacteria-Mediated Bioremediation of Problem Soils
143