Biogeochemical Cycles: Carbon, Nitrogen, and Sulfur

What are the 3 biogeochemical cycling reactions?

Carbon, Nitrogen, and Sulfur redox reactions

Winogradsky Column

A column that has separate layers used to stimulate different environments, allowing bacteria to form distinct bands in the column.

• Used to study microbial interactions and biogeochemical cycles

Photosynthesis

• reducing

• converts CO2 → O2

Glycolysis & Krebs Cycle

• Oxidation

• converts CO2 → O2

Methanogenesis

• reducing

• converts CO2 → CH4

Methane Oxidation

• oxidation

• converts CH4 → CO2

Nitrogen Fixation

• reducing

• converts N2 → NH4

Denitrogenification

• reducing

• NO3 → N2

Ammonification

• Reducing

• N2 → NH4+ or NH3

Nitrification

• oxidation

• NH3 → NO3

What organisms undergo nitrogen cycle reactions?

Rhizobiums and Nitrosomonas

What organisms undergo oxygen cycle reactions?

autotrophs and phototrophs

Anaerobic Respiration

• reducing

• SO4 → H2S (sulfate → hydrogen sulfate)

Sulfur Oxidation

• oxidizing

• H2S → SO4 (hydrogen sulfide → sulfate)

• Lithotrophs

What organisms can and cannot incorporate Nitrogen?

plants cannot incorporate Nitrogen from the air but prokaryotes can using nitrogen fixation.

Steps of the Nitrogen Cycle

1. Nitrogen Fixation: bacteria convert N2 gas into ammonia (NH3)

2. Ammonification: waste products are processed into NH3/NH4+

3. Nitrification: NH4+ (ammonium) oxidized into nitrate (NO2-) then into NO3- by microbes

4. Denitrification: nitrate is used as a terminal electron accepter and converted to nitrate then N2.

What does the sulfur cycle do?

it involves lithotrophic and photosynthetic bacteria (autotrophs) to oxidize H2S to fix CO2.