Lithoautotroph

Lithoautotroph

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Encyclopedia
A lithoautotroph is a microbe which derives energy from reduced
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 compounds of mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 origin. They may also be referred to as chemolithoautotrophs, a type of lithotrophs
Lithotroph
A lithotroph is an organism that uses an inorganic substrate to obtain reducing equivalents for use in biosynthesis or energy conservation via aerobic or anaerobic respiration. Known chemolithotrophs are exclusively microbes; No known macrofauna possesses the ability to utilize inorganic...

, reflecting their autotrophic  metabolic pathways. Lithoautotrophs are exclusively microbes; macrofauna do not possess the capability to utilize mineral sources of energy. For lithoautotrophic bacteria, only inorganic molecules can be used as energy sources. Most lithoautotrophs belong to the domain Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

. The term "Lithotroph" is created from the terms 'lithos' (rock) and 'troph' (consumer); literally, it may be read "eaters of rock." Many lithoautotrophs are extremophiles, but this is not universally so.

Geological processes


Lithoautotrophs participate in many geological processes, such as the weathering
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

 of parent material
Parent material
In soil science, parent material is the underlying geological material in which soil horizons form...

 (bedrock) to form soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, as well as biogeochemical cycling of sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

, potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

, and other elements. They may be present in the deep terrestrial subsurface (they have been found well over 3km below the surface of the planet), in soils, and in endolith
Endolith
An endolith is an organism that lives inside rock, coral, animal shells, or in the pores between mineral grains of a rock. Many are extremophiles, living in places previously thought inhospitable to life...

 communities. As they are responsible for the liberation of many crucial nutrients, and participate in the formation of soil
Pedogenesis
Pedogenesis is the science and study of the processes that lead to the formation of soil ' and first explored by the Russian geologist Vasily Dokuchaev , the so called grandfather of soil science, who determined that soil formed over time as a consequence of...

, lithoautotrophs play a crucial role in the maintenance of life on Earth.

Acid mine drainage


Lithoautotrophic microbial consortia are responsible for the phenomenon known as acid mine drainage
Acid mine drainage
Acid mine drainage , or acid rock drainage , refers to the outflow of acidic water from metal mines or coal mines. However, other areas where the earth has been disturbed may also contribute acid rock drainage to the environment...

, whereby energy-rich pyrite present in mine tailing heaps and in exposed rock faces is metabolized to form sulfites, which form potentially toxic sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

 when dissolved in water. Acid mine drainage drastically alters the acidity and chemistry of groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 and stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

s, and may endanger plant and animal populations. Activity similar to acid mine drainage, but on a much lower scale, is also found in natural conditions such as the rocky beds of glaciers, in soil and talus
Scree
Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles...

, and in the deep subsurface.

Lithoautotrophs are extremely specific in using their energy source. Thus, despite the diversity in using inorganic molecules in order to obtain energy that lithoautotrophs exhibit as a group, one particular lithoautotroph would use only one type of inorganic molecules to get its energy.