Sulfur cycle


Sulfur cycle

Sulfur is one of the constituents of many proteins, vitamins and hormones. It recycles as in other biogeochemical cycles.

The essential steps of the sulfur cycle are:
* Mineralization of organic sulfur to the inorganic form, hydrogen sulfide: (H2S).
* Oxidation of sulfide and elemental sulfur (S) and related compounds to sulfate (SO42–).
* Reduction of sulfate to sulfide.
* Microbial immobilization of the sulfur compounds and subsequent incorporation into the organic form of sulfur.

These are often termed as follows::"Assimilative sulfate reduction" (see also sulfur assimilation) in which sulfate (SO42–) is reduced to organic sulfhydryl (otherwise known as thiol) groups (R–SH) by plants, fungi and various prokaryotes. The oxidation states of sulfur are +6 in sulfate and –2 in R–SH.:"Desulfuration" in which organic molecules containing sulfur can be desulfurated, producing hydrogen sulfide gas (H2S), oxidation state = –2. Note the similarity to deamination.:"Oxidation of hydrogen sulfide" produces elemental sulfur (So), oxidation state = 0. This reaction is done by the photosynthetic green and purple sulfur bacteria and some chemolithotrophs.:Further "oxidation of elemental sulfur" by sulfur oxidizers produces sulfate.:"Dissimilative sulfur reduction" in which elemental sulfur can be reduced to hydrogen sulfide.:"Dissimilative sulfate reduction" in which sulfate reducers generate hydrogen sulfide from sulfate.

Human impact on the sulfur cycle is primarily in the production of sulfur dioxide (SO2) from industry (e.g. burning coal) and the internal combustion engine. Sulfur dioxide can precipitate onto surfaces where it can be oxidized to sulfate in the soil (it is also toxic to some plants), reduced to sulfide in the atmosphere, or oxidized to sulfate in the atmosphere as sulfuric acid, a principal component of acid rain.

External links

* [http://www.lenntech.com/sulfur-cycle.htm Lenntech]
* [http://www.biosci.ohio-state.edu/~mgonzalez/Micro521/23.html Another Lecture]


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • sulfur cycle — ▪ ecology  circulation of sulfur in various forms through nature. Sulfur occurs in all living matter as a component of certain amino acids (amino acid). It is abundant in the soil in proteins (protein) and, through a series of microbial… …   Universalium

  • sulfur cycle — noun the natural cycle which includes the mineralization of organic sulfur to sulfide, oxidation of this to sulfate, and reduction of this to sulfide followed by microbial incorporation of this into organic compounds …   Wiktionary

  • Hybrid sulfur cycle — The hybrid sulfur cycle (HyS) is a sequence of processes used for hydrogen production. It is a variant of the sulfur iodine cycle.The HyS cycle involves a thermochemical and an electrochemical reaction, where the net reaction is the decomposition …   Wikipedia

  • Sulfur-iodine cycle — The sulfur iodine cycle (S I cycle) is a series of thermochemical processes used to produce hydrogen.The S I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other… …   Wikipedia

  • Sulfur — This article is about the chemical element. For other uses, see Sulfur (disambiguation). phosphorus ← sulfur → chlorine …   Wikipedia

  • sulfur bacterium — ▪ biology plural  Sulfur Bacteria,         any of a diverse group of microorganisms capable of metabolizing sulfur and its compounds and important in the sulfur cycle (q.v.) in nature. Some of the common sulfur substances that are used by these… …   Universalium

  • sulfur bacteria — several species of bacteria, esp. of the genera Beggiatoa and Thiobacillus, that have the ability to utilize sulfur or inorganic sulfur compounds as an energy source. [1900 05] * * * Any of a diverse group of bacteria that are capable of… …   Universalium

  • Cycle Soufre-iode — Le cycle iode soufre (cycle IS ou S I en anglais) est une série de processus thermochimiques utilisée pour la production d hydrogène. Il consiste en trois réactions chimiques dont le réactif net est l eau et dont les produits nets sont de l… …   Wikipédia en Français

  • Sulfur hexafluoride — Chembox new Name = Sulfur hexafluoride ImageFile = Sulfur hexafluoride 2D dimensions.png ImageSize = 100px ImageName = Structure and dimensions of the sulfur hexafluoride molecule ImageFile1 = Sulfur hexafluoride 3D balls.png ImageSize1 = 100px… …   Wikipedia

  • Sulfur assimilation — Sulfate reduction and assimilation in plants (APS, adenosine 5 phosphosulfate; Fdred, Fdox, reduced and oxidized ferredoxin; RSH, RSSR, reduced and oxidized glutathione)|right|325pxSulfur is an essential element for growth and physiological… …   Wikipedia


We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.