Synthetic Biology and the Possibilities in Achieving a Plant …
117
to changes in landscape habitats [41, 97, 116, 117]. Further, the consumption of
drinking water with 50 mg/l surpassing nitrate concentrations may cause methemoglobinemia, cancer, birth defects and health restrictions in general. Within the
gastrointestinal tract, bacteria as the Lactobacillus species may reduce nitrate to
nitrite that can react with the ferrous heme group of deoxygenated haemoglobin
and result in methemoglobinemia with hypoxia as typical outcome [6, 40, 114]. In
particular children, not yet possessing the methaemoglobin reductase in contrast to
adults, are suffering (“blue baby syndrome”). High nitrate concentrations consumed
by mothers may affect the neural tube and the central nervous system of the unborn
child. The formation of genotoxic, carcinogenic nitroso-compounds from NO
−
2 overloads may affect also the health of adults through colorectal cancer, thyroid disease,
high blood pressure, and infections in the respiratory tract [6, 19, 27, 43, 80, 83, 89,
96, 98, 115]. Such health risks afford to understand the processes involved in nitrate
reduction.
2 The N-Recycling Processes Nitrification
and Denitrification
Global nitrification and denitrification depend on biological and technical N 2 fixation,
the introduction of ammonia in the N cycle, the oxidation of NH 3 to nitrate under
energy gain and biomass formation, and the reduction of NO
−
3 to NO
−
2 , NO, N 2 O, N 2 ,
or even to NH 3 also out of energy gain and biomass formation reasons (Fig. 1). The
intermediate products NO
−
3 , NO
−
2 , NO, N 2 O of nitrification and denitrification as well
as NH 3 co-shape eutrophication, the atmosphere and the climate [14, 17, 11, 15].
A broad spectrum of nitrifying bacteria and archaea, such as Nitrosomonas
europaea that oxidizes ammonia to the intermediates hydroxylamine, nitrite, and
finally to nitrate, pursue an autotroph living style and are present in soils and WWTPs.
With electrons (e
− ) and protons (H
+ ), elevated to a higher energetic level during
photosynthesis and stored in NH 3 , nitrifying bacteria and archaea gain energy by
oxidizing NH 3 to nitrate and cell biomass by reducing CO 2 with the in NH 3 stored
e
− and H
+ (Fig. 1; [14, 45]). The amo operon thereby regulates nitrification and
the enzyme ammonia monooxygenase (AMO), encoded by the amoABC cluster,
catalyses the oxidation of ammonia to hydroxylamine that is further oxidized to
nitrite, with help of the enzyme hydroxylamine oxidoreductase (HAO). Two c-type
cytochromes, Cc554 and Ccm552, play a critical role in the electron transfer, whereby
electrons are transported via Cc554 from HAO to Ccm552, to quinone or other
terminal electron acceptors [17].
Major end product of the nitrification-denitrification cooperation is N 2 , able to
return to the atmosphere [78]. The enzymes, involved in the reduction of nitrate to
N 2 or even to NH 3 work preferred under use of e
− and H
+ , stored in organic matter,
and in absence of oxygen, but a certain amount of oxygen is tolerated. Also in the
117
to changes in landscape habitats [41, 97, 116, 117]. Further, the consumption of
drinking water with 50 mg/l surpassing nitrate concentrations may cause methemoglobinemia, cancer, birth defects and health restrictions in general. Within the
gastrointestinal tract, bacteria as the Lactobacillus species may reduce nitrate to
nitrite that can react with the ferrous heme group of deoxygenated haemoglobin
and result in methemoglobinemia with hypoxia as typical outcome [6, 40, 114]. In
particular children, not yet possessing the methaemoglobin reductase in contrast to
adults, are suffering (“blue baby syndrome”). High nitrate concentrations consumed
by mothers may affect the neural tube and the central nervous system of the unborn
child. The formation of genotoxic, carcinogenic nitroso-compounds from NO
−
2 overloads may affect also the health of adults through colorectal cancer, thyroid disease,
high blood pressure, and infections in the respiratory tract [6, 19, 27, 43, 80, 83, 89,
96, 98, 115]. Such health risks afford to understand the processes involved in nitrate
reduction.
2 The N-Recycling Processes Nitrification
and Denitrification
Global nitrification and denitrification depend on biological and technical N 2 fixation,
the introduction of ammonia in the N cycle, the oxidation of NH 3 to nitrate under
energy gain and biomass formation, and the reduction of NO
−
3 to NO
−
2 , NO, N 2 O, N 2 ,
or even to NH 3 also out of energy gain and biomass formation reasons (Fig. 1). The
intermediate products NO
−
3 , NO
−
2 , NO, N 2 O of nitrification and denitrification as well
as NH 3 co-shape eutrophication, the atmosphere and the climate [14, 17, 11, 15].
A broad spectrum of nitrifying bacteria and archaea, such as Nitrosomonas
europaea that oxidizes ammonia to the intermediates hydroxylamine, nitrite, and
finally to nitrate, pursue an autotroph living style and are present in soils and WWTPs.
With electrons (e
− ) and protons (H
+ ), elevated to a higher energetic level during
photosynthesis and stored in NH 3 , nitrifying bacteria and archaea gain energy by
oxidizing NH 3 to nitrate and cell biomass by reducing CO 2 with the in NH 3 stored
e
− and H
+ (Fig. 1; [14, 45]). The amo operon thereby regulates nitrification and
the enzyme ammonia monooxygenase (AMO), encoded by the amoABC cluster,
catalyses the oxidation of ammonia to hydroxylamine that is further oxidized to
nitrite, with help of the enzyme hydroxylamine oxidoreductase (HAO). Two c-type
cytochromes, Cc554 and Ccm552, play a critical role in the electron transfer, whereby
electrons are transported via Cc554 from HAO to Ccm552, to quinone or other
terminal electron acceptors [17].
Major end product of the nitrification-denitrification cooperation is N 2 , able to
return to the atmosphere [78]. The enzymes, involved in the reduction of nitrate to
N 2 or even to NH 3 work preferred under use of e
− and H
+ , stored in organic matter,
and in absence of oxygen, but a certain amount of oxygen is tolerated. Also in the