14
K. KirupaSree et al.
1 Introduction
Various industries such as cosmetics, textiles, tanneries emerge worldwide to fulfill
the various requirements of enlarging population. These advancements have put an
increasing burden on the environment by releasing large quantities of hazardous
wastes, heavy metals, metalloids and chemicals that lead to serious problems in an
ecosystem (Ayansina and Olubukola 2017). Heavy metals are naturally occurring
elements that have a high atomic weight and a density at least 5 times greater than
that of water (Tchounwou et al. 2012). The increase in heavy metal concentration in
the environment at alarming rate may directly or indirectly affect plants, microbes,
animals and human beings. Enormous amount of heavy metals are used in various
fungicides and chemical fertilizers, wastewater irrigation and sewage sludge which
in turn contaminates water resources as well as agricultural soils (Akcil et al. 2015).
Copper conjugated pesticides are very expensive and formulated to have fungicidal
and bactericidal actions (CIPAC 1992). Copper-(II) ion (Cu
2+ ) enters the fungal
spores during germination and accumulates until a high concentration is achieved to
kill the spores. However, antifungal activity is restricted to prevent the spore germination. Hence a prophylactic mode of fungicidal action is observed with copper based
fungicides. Unfortunately, the deposition does happen on the crop before fungal
spores begin to germinate indicating the essentiality of environment risk assessments.
A similar mechanism is postulated for antibacterial action of copper based pesticides in day-to-day agriculture by US-EPA (United States Environmental Protection
Agency) in the year 2000. Examples of copper based fungicides include GalbinAr,
Efdalbakirox, Moltifen and Bromix. Waheed and Nahed (2017) have analyzed the
presence of Arsenic (As), Cadmium (Cd) and Lead (Pb) as impurities and copper as
conjugates in the above listed copper based fungicidal formulates before and after
storage at 54 °C for 21 days.
Microbes play an important role in substance turnover of heavy metal contamination which will clean up the metal contaminated sites (Spain and Alm 2003). If
the heavy metal is fewer in concentration it may act as active elements in plants
and microorganisms. For example, Copper (Cu), manganese (Mn), molybdenum
(Mo), nickel (Ni) and zinc (Zn) are actually micronutrients which mean these heavy
metals are needed at very low quantities for the normal growth of plants. Iron (Fe)
is not generally considered as a heavy metal because it is essential for growth and
metabolism of both plants and animals at its optimum level. However when the
above listed heavy metals are presented at supra-optimum levels (i.e., above 0.1%)
they are toxic to plants and rhizosphere microorganisms (Nies 1999).To circumvent
the metal stress, bacteria progress through many types of mechanisms to overcome
the uptake of heavy metal ions. The mechanisms include efflux of metal ions outside
the cell, binding and accumulation of the metal ions inside the cell and reduction of
heavy metal ions to the less toxic states (Nies 1999). Cations of the heavy metals
bind to glutathione in gram negative bacteria, which would result in bisglutathionato
complexes. Bisglutathionato complexes in turn react with the molecular oxygen
forming the Oxidized bisglutathione (Kachur et al. 1998). Reduced forms of heavy
K. KirupaSree et al.
1 Introduction
Various industries such as cosmetics, textiles, tanneries emerge worldwide to fulfill
the various requirements of enlarging population. These advancements have put an
increasing burden on the environment by releasing large quantities of hazardous
wastes, heavy metals, metalloids and chemicals that lead to serious problems in an
ecosystem (Ayansina and Olubukola 2017). Heavy metals are naturally occurring
elements that have a high atomic weight and a density at least 5 times greater than
that of water (Tchounwou et al. 2012). The increase in heavy metal concentration in
the environment at alarming rate may directly or indirectly affect plants, microbes,
animals and human beings. Enormous amount of heavy metals are used in various
fungicides and chemical fertilizers, wastewater irrigation and sewage sludge which
in turn contaminates water resources as well as agricultural soils (Akcil et al. 2015).
Copper conjugated pesticides are very expensive and formulated to have fungicidal
and bactericidal actions (CIPAC 1992). Copper-(II) ion (Cu
2+ ) enters the fungal
spores during germination and accumulates until a high concentration is achieved to
kill the spores. However, antifungal activity is restricted to prevent the spore germination. Hence a prophylactic mode of fungicidal action is observed with copper based
fungicides. Unfortunately, the deposition does happen on the crop before fungal
spores begin to germinate indicating the essentiality of environment risk assessments.
A similar mechanism is postulated for antibacterial action of copper based pesticides in day-to-day agriculture by US-EPA (United States Environmental Protection
Agency) in the year 2000. Examples of copper based fungicides include GalbinAr,
Efdalbakirox, Moltifen and Bromix. Waheed and Nahed (2017) have analyzed the
presence of Arsenic (As), Cadmium (Cd) and Lead (Pb) as impurities and copper as
conjugates in the above listed copper based fungicidal formulates before and after
storage at 54 °C for 21 days.
Microbes play an important role in substance turnover of heavy metal contamination which will clean up the metal contaminated sites (Spain and Alm 2003). If
the heavy metal is fewer in concentration it may act as active elements in plants
and microorganisms. For example, Copper (Cu), manganese (Mn), molybdenum
(Mo), nickel (Ni) and zinc (Zn) are actually micronutrients which mean these heavy
metals are needed at very low quantities for the normal growth of plants. Iron (Fe)
is not generally considered as a heavy metal because it is essential for growth and
metabolism of both plants and animals at its optimum level. However when the
above listed heavy metals are presented at supra-optimum levels (i.e., above 0.1%)
they are toxic to plants and rhizosphere microorganisms (Nies 1999).To circumvent
the metal stress, bacteria progress through many types of mechanisms to overcome
the uptake of heavy metal ions. The mechanisms include efflux of metal ions outside
the cell, binding and accumulation of the metal ions inside the cell and reduction of
heavy metal ions to the less toxic states (Nies 1999). Cations of the heavy metals
bind to glutathione in gram negative bacteria, which would result in bisglutathionato
complexes. Bisglutathionato complexes in turn react with the molecular oxygen
forming the Oxidized bisglutathione (Kachur et al. 1998). Reduced forms of heavy