L19W10_MIC105_NitrogenII

L19W10_MIC105_NitrogenII - 2/24/2010 1 Nitrifcation NH 4...

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Unformatted text preview: 2/24/2010 1 Nitrifcation NH 4 +-> NO 3- * Nitrogen fxation N 2-> NH 4 + Denitrifcation NO 3--> N 2 Anammox NH 4 + + NO 2- -> N 2 Assimilatory Nitrate reduction NO 3--> NH 4 + Nitrogen Cycle Reactions II 2/24/2010 2 Nitrifcation: NH 3-> NO 2--> NO 3- Anammox: NH 4 + + NO 2--> N 2 + 2 H 2 O Denitrifcation & Nitrate Respiration NO 3- -> NO 2- -> NO -> N 2 O -> N 2 l_ > NH 4 + Nitrogen Fixation: N 2-> NH 3 Nitrogen Assimilation: NH 3-> organic nitrogen compounds NO 3--> NH 3-> organic nitrogen compounds (assimilatory nitrate reduction) Ammonifcation: organic nitrogen compounds -> NH 3 Nitrogen Cycle Reactions II * 2/24/2010 3 Nitrifcation: oxidation oF ammonia to nitrate NH 3-> NO 2--> NO 3- 2/24/2010 4 Anion leaching Nitrifcation * Ammonia oxidizers Nitrite oxidizers NH 4 +-> NO 3- 2/24/2010 5 Nitrifcation: oxidation oF ammonia to nitrate Carried out by 2 physiologically distinct groups oF organisms Ammonia oxidizers convert ammonia to nitrite NH 3-> NO 2- (ex. Nitrosococcus) Nitrite oxidizers convert nitrite to nitrate NO 2--> NO 3- (ex. Nitrobacter ) Both groups are chemolithoautotrophs that use the Calvin cycle to fx CO 2 No organisms are currently known to carry out both steps * 2/24/2010 6 Nitrifers * 2/24/2010 7 Nitrifcation: oxidation oF ammonia to nitrate (NO 3- ) Ammonia oxidizing bacteria (AOB) are members oF the and Proteobacteria NH 3 + 1 1 / 2 O 2-> NO 2- + H 2 O G o = -288 kJ/mol * 2/24/2010 8 Nitrifcation: oxidation oF ammonia to nitrate Ammonia oxidizing bacteria (NH 3-> NO 2- ) Key enzymes: 1. A mmonia monooxygenase (AMO) converts ammonia to hydroxylamine (NH 3-> NH 2 OH) AMO is evolutionarily and Functionally related to methane monooxygenase (MMO) which is used by methanotrophs to oxidize methane to methanol (CH 4-> CH 3 OH) 2. Hydroxylamine oxidoreductase catalyzes NH 2 OH -> NO 2- * 2/24/2010 9 Aerobic Ammonia Oxidation Electrons enter the ETC, result in protons pumped and generation of PMF. ATP can be generated as protons enter the cell via a standard ATPase. * 2/24/2010 10 AOBs: obligate autotrophs? Most ammonia oxidizing bacteria are obligate autotrophs . However, the genome of Nitrosomonas europea revealed the presence of genes for a fructose transporter. The organism was found to grow with fructose or pyruvate as sole carbon sources but only in the absence of CO 2 ... AND it still required ammonium as the energy source and electron donor. An example of chemolithoheterotrophy * 2/24/2010 11 Ammonia oxidizing bacterium: Nitrosococcus oceani 2/24/2010 12 Nitrifcation: oxidation oF ammonia to nitrate Nitrite oxidizing bacteria are members oF the , and Proteobacteria and the Nitrospira lineage NO 2- + H 2 O -> NO 3- + 2 H + + 2 e- G o = -74 kJ/mol * 2/24/2010 13 Nitrifcation: oxidation oF ammonia to nitrate Nitrite oxidizing bacteria Key enzyme:...
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L19W10_MIC105_NitrogenII - 2/24/2010 1 Nitrifcation NH 4...

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