12.2 Heavy Metals
Due to the development of various industries, heavy metals are delivered untreated
in the environment with wastes which results in serious environmental pollution and
endanger human survival. Heavy metals like As, Cr, Pb, Hg, Cd and U are always
present in the industrial effluents, which is a major environmental issue because of
their toxic and non-biodegradable character and the extended biological half-lives
making their removal from biological tissues a difficult task (Aiking et al. 1984).
Those ions which have partially or completely filled d-orbitals and atomic
weights ranging from 63.5 to 200.6 with a specific gravity greater than 5 are
known as heavy metals. Living organisms need small amounts of certain heavy
metals like cobalt, copper, iron, manganese, molybdenum and vanadium. However,
a high concentration of these essential metals is toxic to the living organism. Some
other heavy metals like cadmium, chromium, mercury, lead, arsenic and antimony
are especially concern with surface water systems and often transported by runoff
water and pollute water sources downstream from the industrial site. These heavy
metals can bind to the surface of microorganisms and may even go inside the cells.
Inside the microorganism, the heavy metals are chemically transformed as the
microorganism utilizes a chemical reaction to digest food.
These metals pose health problems to those who inhabit these polluted sites.
Metal waste is commonly found in soil, sediments and water. Most probably, metal
contaminants make their entries through breathing, eating, drinking and skin interaction. Metals like mercury, lead and arsenic are harmful to the kidneys, diminish
mental capabilities and cause weakness, headaches, abdominal cramps, diarrhoea
and anaemia (Kristanti et al. 2011). Severe contact with these pollutants can harm
kidney and brain permanently (Kristanti et al. 2011). But metals like cadmium are
very harmful and induce DNA breakage. Industrial sewages contaminated with
metals are discharged into sewage treatment plants which ultimately increase
metal concentrations in the activated sludge. However, arsenic, copper, iron, nickel,
etc. are important in less concentration but cause damage at high concentration
(Baker 1999). Heavy metal contamination causes many health problems like headache, irritability, abdominal pain and various symptoms associated with nervous
system, anxiety, bladder and kidney cancer (Baker 1981) through the transfer of
important nutritional minerals from their original place, thereby blocking their
biological function or accumulating to disrupt the function of important organs
and glands like heart, brain, kidneys, bone and liver (Balasubramanian et al.
2008). The microbial world is diverse, because of which microorganisms can change
themselves to toxic concentrations of heavy metals and turn into “metal resistant”
(Bogacka 2011; Gupta et al. 2016).
12 Remediation of Heavy Metals Through Genetically Engineered Microorganism
317
Due to the development of various industries, heavy metals are delivered untreated
in the environment with wastes which results in serious environmental pollution and
endanger human survival. Heavy metals like As, Cr, Pb, Hg, Cd and U are always
present in the industrial effluents, which is a major environmental issue because of
their toxic and non-biodegradable character and the extended biological half-lives
making their removal from biological tissues a difficult task (Aiking et al. 1984).
Those ions which have partially or completely filled d-orbitals and atomic
weights ranging from 63.5 to 200.6 with a specific gravity greater than 5 are
known as heavy metals. Living organisms need small amounts of certain heavy
metals like cobalt, copper, iron, manganese, molybdenum and vanadium. However,
a high concentration of these essential metals is toxic to the living organism. Some
other heavy metals like cadmium, chromium, mercury, lead, arsenic and antimony
are especially concern with surface water systems and often transported by runoff
water and pollute water sources downstream from the industrial site. These heavy
metals can bind to the surface of microorganisms and may even go inside the cells.
Inside the microorganism, the heavy metals are chemically transformed as the
microorganism utilizes a chemical reaction to digest food.
These metals pose health problems to those who inhabit these polluted sites.
Metal waste is commonly found in soil, sediments and water. Most probably, metal
contaminants make their entries through breathing, eating, drinking and skin interaction. Metals like mercury, lead and arsenic are harmful to the kidneys, diminish
mental capabilities and cause weakness, headaches, abdominal cramps, diarrhoea
and anaemia (Kristanti et al. 2011). Severe contact with these pollutants can harm
kidney and brain permanently (Kristanti et al. 2011). But metals like cadmium are
very harmful and induce DNA breakage. Industrial sewages contaminated with
metals are discharged into sewage treatment plants which ultimately increase
metal concentrations in the activated sludge. However, arsenic, copper, iron, nickel,
etc. are important in less concentration but cause damage at high concentration
(Baker 1999). Heavy metal contamination causes many health problems like headache, irritability, abdominal pain and various symptoms associated with nervous
system, anxiety, bladder and kidney cancer (Baker 1981) through the transfer of
important nutritional minerals from their original place, thereby blocking their
biological function or accumulating to disrupt the function of important organs
and glands like heart, brain, kidneys, bone and liver (Balasubramanian et al.
2008). The microbial world is diverse, because of which microorganisms can change
themselves to toxic concentrations of heavy metals and turn into “metal resistant”
(Bogacka 2011; Gupta et al. 2016).
12 Remediation of Heavy Metals Through Genetically Engineered Microorganism
317