Biogeochemical cycles

What are the main steps of the carbon cycle?

1. Carbon fixation - CO2 to organic matter by photo and chemoautotrophy

2. Respiration/Fermentation - Organic matter to CO2 by heterotrophs

3. Methanogenesis - Reduction of CO2 to CH4 by anaerobic archaea methanogens (anaerobic)

4. Methanotrophy - Oxidation of methane by aerobic bacter and anaerobic archaea and denitrifiers

What organisms perform carbon fixation?

• oxygenic - microbes, marine cyanobacteria, diatoms

• anoxygenic - bacterla/archael chemolithoautotrophy

What is methanogenesis and what organisms perform this?

production of methane from organic matter, CO2, or H2. done by methanogenic archaea

What steps of the carbon cycle are anaerobic?

• Carbon fixation from CO2 to organic matter sometimes

• Reduction of Co2 to CH4

What role does the molecules play in the nitrogen cycle?

• NH4+/NH3

• NO3-

• NO2-

• N2

• NH4+/NH3 - e- donor, reduced

• NO3- e- acceptor, fully oxidized

• NO2- e- acceptor/donor, intermediate

• N2

Briefly describe the steps of the nitrogen cycle

1. Nitrogen fixation - N2 into usable NH3

2. Assimilation - conversion of NH3 into organic nitrogen within organisms, DNA, proteins, etc.

3. Ammonification/Mineralization - decomposing organic matter (DNA, proteins, etc) into ammonia (NH4)

4. Nitrification- NH4/NH3 to NO2- to NO3-

5. Denitrification - Conversion of NO3-/NO2- to N2 gas

What happens in nitrogen fixation and what organisms perform this?

• N2 to usable NH3

• done by diazotrophs (bacteria and archaea that fix atmospheric nitrogen into usable forms)

• done by symbiotes (ex. rhizobium) or free living bacteria

• Nitrogenase enzyme

Describe assimilation

The process of converting ammonia (NH3) into organic nitrogen compounds, like amino acids and nucleotides, within living organisms. done by decomposers

Describe the steps of nitrification

• oxidation of ammonia to NO3-

• NH3- to NO2- (Nitrite) by bacteria/archaea

• NO2- to NO3- (Nitrate) by bacteria

• aerobic process, requires O2

Is nitrification aerobic or anaerobic?

aerobic

Describe denitrification

• conversion of NO3- and NO2- to N2 gas

• occurs in anaerobic environments like soil and sediment

• done by diverse groups of chemoorganotrophs bacteria (Bacillus, psuedomonas)

• detrimental to soil fertility

Describe anamoox

• anaerobic oxidation of ammonium (NH4+) to nitrogen gas (N2) using nitrite (NO2-) as the electron acceptor.

• carried out by specialized bacteria

• role in wastewater treatment

Briefly describe the phosphorous cycle

• phosphorous needed for ATP and DNA

• phosphorous leaches from weathering and agriculture runoff

• forms organic and inorganic phosphate reserves ex. in ground

• organic phosphate easily recycled by microbes

• inorganic phosphate forms insoluble complexes

Briefly describe the sulfur cycle

1. sulfate (SO42-) reduced for amino acids/biosynthesis

2. Sulfate reduced to H2S (sulfide)

3. sulfide serves as an electron source for anaerobic photosynthetic microbes, becomes elemental sulfur and sulfate (SO4 2-)

What is methanotrophy and what cycle is it important in?

• CH4 oxidized to CO2

• occurs in carbon cycle

• performed by aerobic bacteria and anaerobic archaea

Describe the production and removal of methane

• methane produced from CO2 by methanogenic archaea

• methane removed by methanotrophs and turned into CO2

Why is removing CH4 (methane) from the environment by methanotrophs important?

reduces greenhouse gases

What are the formulas for nitrate and nitrite?

• NO3-

• NO2-

Give a specific example of nitrogen fixation

conversion of N2 to usable NH3 ex. by rhizobium species

Give a specific example of ammonification

organic nitrogen (DNA, proteins, etc.) into ammonia ex. by decomposers

Give a specific example of nitrification

• conversion of NH3 to NO2- to NO3-

• ex. NH# to NO2- by nitrospira species

Give a specific example of denitrification

• conversion of NO3- to N2 gas

• ex. by denitrifying bacteria such as Pseudomonas

What role do nitrifying and denitrifying bacteria have in wastewater treatment?

They convert ammonia to nitrate and then to nitrogen gas, reducing nitrogen levels in wastewater.