BIOMI 2900 Lecture 29

Features of Biogeochemical Cycles: Each step is mediated by a set of?

organisms

Features of Biogeochemical Cycles: Cycling replenishes what over time?

reactant

Features of Biogeochemical Cycles: Cycling couples the what of reactants, and this typically requires coupling of what two processes?

oxidation and reduction

aerobic and anaerobic processes

Features of Biogeochemical Cycles: Steps can be driven by what two processes?

Assimilatory or Dissimilatory processes

Features of Biogeochemical Cycles: Assimilatory: molecule is assimilated into?

biomass (anabolic reactions)

Features of Biogeochemical Cycles: Dissimilatory: molecule is transformed but?

nor assimilated (catabolic reactions)

Oxidized vs Reduced

The Nitrogen Cycle: Animals vs Plants

N2 Fixation

What is the key enzyme for Nitrogen Fixation?

Nitrogenase (NifH, NifK, NifD)

Assimilatory, requires lots of what two things?

ATP and reducing power (e - )

Nitrogen Fixation: N2 from air is fixed into?

NH4 +

Nitrogenase is inhibited by? repressed by?

Inhibited by O2, repressed by NH4 +

Ancient enzyme, HGT common, found in?

diverse microbes

Ancient enzyme, HGT common, found in diverse microbes. What are two examples?

1. Cyanobacteria (oxygenic photo-litho-autotrophs)

2. Rhizobia (aerobic chemo-organo-heterotrophs)

N2 Fixation: Rhizobia: N2 fixing symbionts of?

legumes

(e.g. bean, clover, alfalfa, etc)

N2 Fixation: Rhizobia: Microbes provide? to ?

N to plant

N2 Fixation: Rhizobia: Plant provides what 3 things?

1. C and energy source

2. A nice safe place to live

3. Leghemoglobin (regulates O2 )

Nitrification: (Bacterial Phyla: Proteobacteria, Nitrospira) (Archaeal Phlya: Thaumarchaeota)

Nitrification metabolism is by what 2 things?

Chemo-litho-autotrophs

obligate aerobes

Key enzyme for nitrification?

Ammonia monooxygenase (AmoA)

Electron donors for nitrification?

Electron acceptors?

1. Donors: NH4 + or NO2 -

2. Acceptors: O2

Carbon Sources for Nitrification?

CO2 (autotrophic)

Habitat for Nitrification?

widespread in oxic soil and aquatic habitats

Ammonia oxidizers vs Nitrite oxidizers:

Nitrification

Which of the following is a potential product of denitrification?

A

Denitrification:

Denitrification (Phylogenetically diverse): Metabolism by what two things?

Chemo-organo-heterotrophs, facultative anaerobes (typically)

Electron Donors? Electron acceptors for Denitrification?

Electron Donors: Organic carbon (typically)

Electron Acceptors: NO3 - , NO2 -

Carbon Sources for Denitrification?

Organic carbon

Habitat for Denitrification?

widespread anoxic soil and aquatic habitats

Denitrification returns N to the atmosphere as what two things?

N2 or N2O gas

Denitrification

Denitrification: NADH formed using e - from the?

electron donor (which is usually organic carbon, e.g. glucose)

Denitrification Examples: Fish Tank

N-cycle Example Agriculture: Haber-Bosch process ia a chemical fixation of N2 into?

NH3

N-cycle Example Agriculture: Haber-Bosch process is used to make? It requires LOTS of?

fertilizer

natural gas (energy)

Humans have more than doubled the input of NH3 into the biosphere though what 2 things?

Haber-Bosch process and the use of legumes.

N-cycle Examples: Agriculture N in fertilizer is mostly in?

NH4 +

What converts NH4 + to NO3?

Nitrifiers

Nitrifiers convert NH4 + to NO3

NO3- moves with water in runoff, a cause of?

eutrophication

Denitrifiers convert NO3 into what two things?

N2O and N2 gasses

• N2O has ~310x more powerful GWP than CO2

• N2O promotes acid rain (made into nitric acid in atmosphere)

Eutrophication

Eutrophication: nutrient enrichment induced water pollution: Caused by?

N and P in runoff (from fertilizers)

Ocean Dead Zones (anoxia)

Anthropogenic contributions to N2O emissions