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The important sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. [1]
The slow cycle operates through rocks, including volcanic and tectonic activity. There are fast and slow biogeochemical cycles. Fast cycle operate in the biosphere and slow cycles operate in rocks. Fast or biological cycles can complete within years, moving substances from atmosphere to biosphere, then back to the atmosphere.
The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Earth's main sulfur sink is the oceans SO 4 2−, where it is the major oxidizing agent. [47]
Sulfur reduction occurs in plants, fungi, and many bacteria. [10] Sulfate can serve as an electron acceptor in anaerobic respiration and can also be reduced for the formation of organic compounds. Sulfate-reducing bacteria reduce sulfate and other oxidized sulfur compounds, such as sulfite, thiosulfate, and elemental sulfur, to sulfide.
Photosynthesis (/ ˌ f oʊ t ə ˈ s ɪ n θ ə s ɪ s / FOH-tə-SINTH-ə-sis) [1] is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabolism.
Although the biological oxidation of reduced sulfur compounds competes with abiotic chemical reactions (e.g. the iron-mediated oxidation of sulfide to iron sulfide (FeS) or pyrite (FeS 2)), [11] thermodynamic and kinetic considerations suggest that biological oxidation far exceeds the chemical oxidation of sulfide in most environments. [5]
2 S, which is oxidized to sulfur (hence the name "green sulfur bacteria"). Purple bacteria and green sulfur bacteria occupy relatively minor ecological niches in the present day biosphere. They are of interest because of their importance in precambrian ecologies, and because their methods of photosynthesis were the likely evolutionary ...
Referring to the latest definition, Chromatiaceae family includes only those purple sulfur bacteria that perform anoxygenic photosynthesis and store elemental sulfur inside their cells. This is in line with the first Molisch definition of the Thiorhodaceae group and reflects the distance, but phylogenetic correlation between the two families. [11]