Editing Sulfur (section)

=== Transferring sulfur between inorganic and biomolecules ===
{{See also|Sulfur cycle|Sulfur metabolism}}

In the 1880s, while studying ''[[Beggiatoa]]'' (a bacterium living in a sulfur rich environment), [[Sergei Winogradsky]] found that it oxidized [[hydrogen sulfide]] (H<sub>2</sub>S) as an energy source, forming intracellular sulfur droplets. Winogradsky referred to this form of metabolism as inorgoxidation (oxidation of inorganic compounds).<ref>{{Cite journal |last=Dworkin |first=Martin |date=March 2012 |title=Sergei Winogradsky: a founder of modern microbiology and the first microbial ecologist |journal=FEMS Microbiology Reviews |volume=36 |issue=2 |pages=364–379 |doi=10.1111/j.1574-6976.2011.00299.x |issn=1574-6976 |pmid=22092289|doi-access=free }}</ref> Another contributor, who continued to study it was [[Selman Waksman]].<ref>{{Cite journal |last1=Waksman |first1=S. A. |last2=Starkey |first2=R. L. |title=On the Growth and Respiration of Sulfur-Oxidizing Bacteria |date=1923-01-20 |journal=The Journal of General Physiology |volume=5 |issue=3 |pages=285–310 |doi=10.1085/jgp.5.3.285 |issn=0022-1295 |pmc=2140527 |pmid=19871997}}</ref> Primitive bacteria that live around deep ocean [[hydrothermal vent|volcanic vents]] oxidize hydrogen sulfide for their nutrition, as discovered by [[Robert Ballard]].<ref name="BBC_Elements-2014" />

Sulfur oxidizers can use as energy sources reduced sulfur compounds, including hydrogen sulfide, elemental sulfur, [[sulfite]], [[thiosulfate]], and various [[polythionates]] (e.g., [[tetrathionate]]).<ref>{{cite journal |author= Pronk JT |author2= Meulenberg R |author3= Hazeu W |author4= Bos P |author5= Kuenen JG |date= 1990 |title= Oxidation of reduced inorganic sulphur compounds by acidophilic thiobacilli |journal= FEMS Microbiology Letters |volume= 75 |issue= 2–3 |pages= 293–306 |doi= 10.1111/j.1574-6968.1990.tb04103.x |df= dmy-all|doi-access= free }}</ref> They depend on enzymes such as [[sulfur dioxygenase|sulfur oxygenase]] and [[sulfite oxidase]] to oxidize sulfur to sulfate. Some [[lithotroph]]s can even use the energy contained in sulfur compounds to produce sugars, a process known as [[chemosynthesis]]. Some [[bacteria]] and [[archaea]] use hydrogen sulfide in place of water as the [[electron donor]] in chemosynthesis, a process similar to [[photosynthesis]] that produces sugars and uses oxygen as the [[electron acceptor]]. Sulfur-based chemosynthesis may be simplifiedly compared with photosynthesis:

{{block indent|H<sub>2</sub>S + CO<sub>2</sub> → sugars + S}}
{{block indent|H<sub>2</sub>O + CO<sub>2</sub> → sugars + O<sub>2</sub>}}

There are bacteria combining these two ways of nutrition: [[green sulfur bacteria]] and [[purple sulfur bacteria]].<ref>{{Citation |last1=Frigaard |first1=Niels-Ulrik |title=Sulfur Metabolism in Phototrophic Sulfur Bacteria |date=2008-01-01 |url=https://www.sciencedirect.com/science/article/pii/S0065291108000027 |volume=54 |pages=103–200 |editor-last=Poole |editor-first=Robert K. |publisher=Academic Press |language=en |access-date=2022-05-17 |last2=Dahl |first2=Christiane|series=Advances in Microbial Physiology |doi=10.1016/S0065-2911(08)00002-7 |pmid=18929068 |isbn=9780123743237 }}</ref> Also sulfur-oxidizing bacteria can go into symbiosis with larger organisms, enabling the later to use hydrogen sulfide as food to be oxidized. Example: the [[giant tube worm]].<ref>{{Cite journal |last=Cavanaugh |first=Colleen M. |date=1994 |title=Microbial Symbiosis: Patterns of Diversity in the Marine Environment |journal=American Zoologist |volume=34 |pages=79–89 |doi=10.1093/icb/34.1.79 |doi-access=free }}</ref>

There are [[sulfate-reducing bacteria]], that, by contrast, "breathe sulfate" instead of oxygen. They use organic compounds or molecular hydrogen as the energy source. They use sulfur as the electron acceptor, and reduce various oxidized sulfur compounds back into sulfide, often into hydrogen sulfide. They can grow on other partially oxidized sulfur compounds (e.g. thiosulfates, thionates, polysulfides, sulfites).

There are studies pointing that many deposits of native sulfur in places that were the bottom of [[Tethys Ocean|the ancient oceans]] have biological origin.<ref>{{Cite journal |last1=Jones |first1=Galen E. |last2=Starkey |first2=Robert L. |last3=Feely |first3=Herbert W. |last4=Kulp |first4=J. Laurence |date=1956-06-22 |title=Biological Origin of Native Sulfur in Salt Domes of Texas and Louisiana |url=https://www.science.org/doi/10.1126/science.123.3208.1124 |journal=Science |language=en |volume=123 |issue=3208 |pages=1124–1125 |doi=10.1126/science.123.3208.1124 |pmid=17793426 |bibcode=1956Sci...123.1124J |issn=0036-8075}}</ref><ref>{{Cite journal |last1=Philip |first1=G. |last2=Wali |first2=A. M. A. |last3=Aref |first3=M. A. M. |date=1994-09-01 |title=On the origin of native sulfur deposits in Gebel El Zeit, Gulf of Suez, Egypt |url=https://doi.org/10.1007/BF03175232 |journal=Carbonates and Evaporites |language=en |volume=9 |issue=2 |pages=223–232 |doi=10.1007/BF03175232 |bibcode=1994CarEv...9..223P |s2cid=128827551 |issn=1878-5212}}</ref><ref>{{Cite web |title=Petrography and mineralogy of the crystalline limestone of Fatha Formation from Mishraq area, Iraq |url=https://www.researchgate.net/publication/330038794 |access-date=2022-04-15 |website=ResearchGate |language=en}}</ref> These studies indicate that this native sulfur have been obtained through biological activity, but what is responsible for that (sulfur-oxidizing bacteria or sulfate-reducing bacteria) is still unknown for sure.

Sulfur is absorbed by [[plant]]s [[root]]s from soil as [[sulfate]] and transported as a phosphate ester. Sulfate is reduced to sulfide via sulfite before it is incorporated into [[cysteine]] and other organosulfur compounds.<ref name="Heldt-1996">{{cite book |last=Heldt |first=Hans-Walter |title=Pflanzenbiochemie |publisher=Spektrum Akademischer Verlag |year=1996 |isbn=978-3-8274-0103-8 |place=Heidelberg |pages=321–333 |language=de}}</ref>

{{block indent|{{chem2|SO4(2-)}} → {{chem2|SO3(2-)}} → {{chem2|H2S}} → cysteine (thiol) → methionine (thioether)}}

While the plants' role in transferring sulfur to animals by [[food chain]]s is more or less understood, the role of sulfur bacteria is just getting investigated.<ref>{{Cite journal |last1=Kuenen |first1=J. G. |last2=Beudeker |first2=R. F. |date=1982-09-13 |title=Microbiology of thiobacilli and other sulphur-oxidizing autotrophs, mixotrophs and heterotrophs |url=https://pubmed.ncbi.nlm.nih.gov/6127737/ |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=298 |issue=1093 |pages=473–497 |doi=10.1098/rstb.1982.0093 |issn=0962-8436 |pmid=6127737|bibcode=1982RSPTB.298..473K }}</ref><ref>{{Cite journal |last1=Wasmund |first1=Kenneth |last2=Mußmann |first2=Marc |last3=Loy |first3=Alexander |date=August 2017 |title=The life sulfuric: microbial ecology of sulfur cycling in marine sediments: Microbial sulfur cycling in marine sediments |journal=Environmental Microbiology Reports |language=en |volume=9 |issue=4 |pages=323–344 |doi=10.1111/1758-2229.12538 |pmc=5573963 |pmid=28419734}}</ref>