Chemotroph

A black smoker in the Atlantic Ocean providing energy and nutrients

Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototrophs, which utilize solar energy. Chemotrophs can be either autotrophic or heterotrophic.

Chemoautotroph

Chemoautotrophs (or chemotrophic autotroph) (Greek: Chemo (χημία) = chemical, auto (αὐτός) = self, troph (τροφιά) = nourishment), in addition to deriving energy from chemical reactions, synthesize all necessary organic compounds from carbon dioxide. Chemoautotrophs use inorganic energy sources, such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia. Most are bacteria or archaea that live in hostile environments such as deep sea vents and are the primary producers in such ecosystems. Chemoautotrophs generally fall into several groups: methanogens, halophiles, sulfur oxidizers and reducers, nitrifiers, anammox bacteria, and thermoacidophiles. Chemolithotrophic growth could be dramatically fast, such as Thiomicrospira crunogena with a doubling time around one hour.[1]

Chemoheterotroph

Chemoheterotrophs (or chemotrophic heterotrophs) (Gr: Chemo (χημία) = chemical, hetero (ἕτερος) = (an)other, troph (τροφιά) = nourishment) are unable to fix carbon to form their own organic compounds. Chemoheterotrophs can be chemolithoheterotrophs, utilizing inorganic energy sources such as sulfur or chemoorganoheterotrophs, utilizing organic energy sources such as carbohydrates, lipids, and proteins.[2][3][4][5]

Iron- and manganese-oxidizing bacteria

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.

Manganese-oxidizing bacteria also make use of igneous lava rocks in much the same way; by oxidizing Mn2+ into Mn4+. Manganese is much rarer than iron in oceanic crust, but is much easier for bacteria to extract from igneous glass. In addition, each manganese oxidation yields approximately 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.

Flowchart

Flowchart to determine if a species is autotroph, heterotroph, or a subtype

See also

Notes

  1. The Carbon-Concentrating Mechanism of the Hydrothermal Vent Chemolithoautotroph Thiomicrospira crunogena J Bacteriol. 2005 August; 187(16): 5761–5766
  2. Davis, Mackenzie Leo; et al. (2004). Principles of environmental engineering and science. 清华大学出版社. p. 133. ISBN 978-7-302-09724-2.
  3. Lengeler, Joseph W.; Drews, Gerhart; Schlegel, Hans Günter (1999). Biology of the Prokaryotes. Georg Thieme Verlag. p. 238. ISBN 978-3-13-108411-8.
  4. Dworkin, Martin (2006). The Prokaryotes: Ecophysiology and biochemistry (3rd ed.). Springer. p. 989. ISBN 978-0-387-25492-0.
  5. Bergey, David Hendricks; Holt, John G. (1994). Bergey's manual of determinative bacteriology (9th ed.). Lippincott Williams & Wilkins. p. 427. ISBN 978-0-683-00603-2.

References

1. Katrina Edwards. Microbiology of a Sediment Pond and the Underlying Young, Cold, Hydrologically Active Ridge Flank. Woods Hole Oceanographic Institution.

2. Coupled Photochemical and Enzymatic Mn(II) Oxidation Pathways of a Planktonic Roseobacter-Like Bacterium Colleen M. Hansel and Chris A. Francis* Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115 Received 28 September 2005/ Accepted 17 February 2006

This article is issued from Wikipedia - version of the Thursday, January 21, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.