|
==Quimioheterótrofos==
Os '''quimioheterótrofos''' son incapaces de [[fixación do carbono|fixar o carbono]] para formar os seus propios compostos orgánicos, polo que deben adquirir compostos orgánicos xa formados do seu medio. Os quimioheterótrofos poden ser quimiolitoheterótrofos (algúns [[procariota]]s), que utilizan fontes de electróns inorgánicas para producir enerxía como o xofre, ou quimioorganoheterótrofos (animais, fungos, protozoos, moitos procariotas), que utilizan fontes de orgánicas de enerxía (e de carbono) como [[carbohidrato]]s, [[lípido]]s, e [[proteína]]s.<ref>{{cite book | last= Davis| first= Mackenzie Leo, et al.| title= Principles of environmental engineering and science| year= 2004| publisher=清华大学出版社| page= 133| url= http://books.google.com/books?id=e0OsNiQthNQC&pg=PA133&dq=chemoheterotroph&lr=&cd=41#v=onepage&q=&f=false| isbn= 978-7-302-09724-2}}</ref><ref>{{cite book | last1= Lengeler| first1= Joseph W.| last2= Drews| first2= Gerhart| last3= Schlegel| first3= Hans Günter| title= Biology of the Prokaryotes| year= 1999| publisher= Georg Thieme Verlag| page= 238| url= http://books.google.com/books?id=MiwpFtTdmjQC&pg=PA238&dq=chemolithoheterotroph+sulfur+bacteria&cd=6#v=onepage&q=chemolithoheterotroph%20sulfur%20bacteria&f=false| isbn= 978-3-13-108411-8}}</ref><ref>{{cite book | last= Dworkin| first= Martin| title= The Prokaryotes: Ecophysiology and biochemistry| year= 2006| edition=3rd| publisher= Springer| page= 989| url= http://books.google.com/books?id=uleTr2jKzJMC&pg=PA989&dq=chemolithoheterotroph+sulfur+bacteria&cd=3#v=onepage&q=chemolithoheterotroph%20sulfur%20bacteria&f=false| isbn= 978-0-387-25492-0}}</ref><ref>{{cite book | last= Bergey| first= David Hendricks| last2= Holt| first2= John G.| title= Bergey's manual of determinative bacteriology| year= 1994| edition=9th| publisher= Lippincott Williams & Wilkins| page= 427| url= http://books.google.com/books?id=jtMLzaa5ONcC&pg=PA427&dq=chemolithotrophic+sulfur+bacteria&cd=1#v=onepage&q=chemolithotrophic%20sulfur%20bacteria&f=false| isbn= 978-0-683-00603-2}}</ref>
==Un exemplo: As bacterias oxidantes do ferro e manganeso==
In the deep oceans, iron-oxidizing bacteria derive their energy needs by oxidizing iron(II) to iron(III). The extra electron obtained from this reaction powers the cells, replacing or augmenting traditional [[phototrophism]].
*In general, iron-oxidizing bacteria can exist only in areas with high iron concentrations, such as new lava beds or areas of hydrothermal activity (where there is dissolved Fe). Most of the ocean is devoid of iron, due to both the oxidative effect of dissolved oxygen in the water and the tendency of [[prokaryotes]] to take up the iron.
*Lava beds supply bacteria with iron straight from the Earth's mantle, but only newly formed [[igneous]] rocks have high enough levels of unoxidized iron. In addition, because oxygen is necessary for the reaction, these bacteria are much more common in the upper ocean, where oxygen is more abundant.
*What is still unknown, though, is how exactly iron bacteria extract the iron out of the rock. It is accepted that some mechanism exists that eats away at the rock, perhaps through specialized [[enzyme]]s or compounds that bring more FeO to the surface. It has been long debated about how much of the weathering of the rock is due to [[biotic component]]s and how much can be attributed to [[abiotic component]]s.
*Hydrothermal vents also release large quantities of dissolved iron into the deep ocean, allowing bacteria to survive. In addition, the high thermal gradient around vent systems means a wide variety of bacteria can coexist, each with its own specialized temperature niche.
*Regardless of the [[catalytic]] method used, chemoautotrophic bacteria provide a significant but frequently overlooked food source for deep sea ecosystems - which otherwise receive limited sunlight and organic nutrients.
[[Manganese]]-oxidizing bacteria also make use of igneous lava rocks in much the same way—by oxidizing Mn<sup>2+</sup> into Mn<sup>4+</sup>. Manganese is much rarer than iron in oceanic crust, but is much easier for bacteria to extract from the igneous glass. In addition, each manganese oxidation yields around twice the energy as an iron oxidation due to the gain of twice the number of electrons. Much still remains unknown about manganese-oxidizing bacteria because they have not been cultured and documented to any great extent.
==Notas==
| 