Jump to ContentJump to Main Navigation
Processes in Microbial Ecology$
Users without a subscription are not able to see the full content.

David L. Kirchman

Print publication date: 2011

Print ISBN-13: 9780199586936

Published to Oxford Scholarship Online: December 2013

DOI: 10.1093/acprof:oso/9780199586936.001.0001

Show Summary Details
Page of

PRINTED FROM OXFORD SCHOLARSHIP ONLINE (www.oxfordscholarship.com). (c) Copyright Oxford University Press, 2020. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 27 January 2020

The nitrogen cycle

The nitrogen cycle

Chapter:
(p.217) Chapter 12 The nitrogen cycle
Source:
Processes in Microbial Ecology
Author(s):

David L. Kirchman

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780199586936.003.0012

Nitrogen is required for the biosynthesis of many compounds occurring in organisms and, unlike phosphorus – another element often limiting growth in many environments – can take on many oxidation states, ranging from -3 to +5. Consequently, nitrogen compounds can act as either electron donors (chemolithotrophy) or electron acceptors (anaerobic respiration). The nitrogen cycle starts with nitrogen fixation, the reduction of nitrogen gas to ammonium. Nitrogen fixation is carried out only by prokaryotes, mainly some cyanobacteria and heterotrophic bacteria. The ammonium resulting from nitrogen fixation is quickly used by many organisms for biosynthesis, being preferred over nitrate as a nitrogen source. It is also oxidized aerobically by chemolithoautotrophic bacteria and archaea during the first step of nitrification. The second step, nitrite oxidation, is carried out by other microbes not involved in ammonia oxidation, resulting in the formation of nitrate, which can then be reduced to nitrogen gas or nitrous oxide during denitrification, or to ammonium. Nitrogen gas is also released by anaerobic oxidation of ammonium, which is carried out by bacteria in the Planctomycetes phylum. The anaerobic ammonium oxidation pathway seems most important in producing nitrogen gas in deep oceanic sediments receiving low fluxes of organic material. Another gas in the nitrogen cycle – nitrous oxide – is a greenhouse gas produced by ammonia-oxidizing microbes. Most models indicate that the global nitrogen cycle is in balance, with losses from nitrogen gas production equalling gains via nitrogen fixation.

Keywords:   nitrogenase, heterocysts, diazotrophs, ammonium assimilation, ammonium regeneration, new production, anammox, Anabaena, Trichodesmium, Rhizobium

Oxford Scholarship Online requires a subscription or purchase to access the full text of books within the service. Public users can however freely search the site and view the abstracts and keywords for each book and chapter.

Please, subscribe or login to access full text content.

If you think you should have access to this title, please contact your librarian.

To troubleshoot, please check our FAQs , and if you can't find the answer there, please contact us .