Mediaspace scheduled maintenance: Aug 25, 2026 07:00 - 12:00 AM. During this time, videos will be temporarily unavailable. Check status updates.

Lecture

Nitrogen cycle: Key Processes and Enzymes

Description

This lecture covers the nitrogen cycle, focusing on the extensive cycling of nitrogen mediated by microbes. It discusses the nitrogen mass balance, oxidation states of key nitrogen compounds, and the processes involved in nitrogen cycling such as N₂ fixation, nitrification, denitrification, and more. The lecture also highlights the key enzymes involved in nitrogen cycling and the impact of human activities on the nitrogen cycle.

Official source

Related concepts (25)

Nitrogen cycle

The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen.

Nitrogen fixation

Nitrogen fixation is a chemical process by which molecular nitrogen (N2), which has a strong triple covalent bond, is converted into ammonia (NH3) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).

Nitrogen

Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element in air.

Nitrification

Nitrification is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea.

Denitrification

Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter.

Related lectures (32)

Sulfur and Nitrogen Cycles

Explores the environmental significance of sulfur and nitrogen cycles, including key microbial processes and organisms involved.

Nitrification and Anammox

Covers nitrification and anammox processes, explaining the oxidation of ammonium under different conditions and their significance in water biogeochemistry.

Nitrogen and Sulfur Cycles in Biogeochemistry

Explores the nitrogen and sulfur cycles, focusing on ammonia oxidation, nitrification, anammox, and microbial networks in different environments.