Lithotroph
Encyclopedia
A lithotroph is an organism
that uses an inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis
(e.g., carbon dioxide fixation) or energy
conservation via aerobic or anaerobic respiration
. Known chemolithotrophs are exclusively microbes; No known macrofauna
possesses the ability to utilize inorganic compounds as energy sources. Macrofauna and lithotrophs can form symbiotic relationships, in which case the lithotrophs are called "prokaryotic symbionts." An example of this is chemolithotrophic bacteria in deep sea worms or plastids, which are organelles within plant cells that may have evolved from photolithotrophic cyanobacteria-like organisms. Lithotrophs belong to either the domain Bacteria
or the domain Archaea
. The term "Lithotroph" is created from the terms 'lithos' (rock) and 'troph' (consumer), meaning the "eaters of rock." Many lithoautotrophs are extremophiles, but this is not universally so.
Different from a lithotroph is an organotroph
, an organism which gets its reducing agents from the catabolism
of organic compounds.
compounds (rich in electron
s).
s - are oxidized in the cell
, and the electrons are channeled into respiratory chains, ultimately producing ATP
. The electron acceptor can be oxygen
(in aerobic
bacteria), but a variety of other electron acceptors, organic
and inorganic, are also used by various species
. Unlike water, the hydrogen compounds used in chemosynthesis are high in energy. Other lithotrophs are able to directly utilize inorganic substances, e.g., iron, hydrogen sulfide, elemental sulfur, or thiosulfate, for some or all of their energy needs.
Here are a few examples of chemolithotrophic pathways, any of which may use oxygen, sulfur or other molecules as electron acceptors:
source for the synthesis of their cells. They choose one of three options:
, nitrogen
, and other elements
. They may be present in the deep terrestrial subsurface (they have been found well over 3 km below the surface of the planet), in soils, and in endolith
communities. As they are responsible for the liberation of many crucial nutrients, and participate in the formation of soil, lithotrophs play a critical role in the maintenance of life on Earth.
Lithotrophic microbial consortia are responsible for the phenomenon known as acid mine drainage
, whereby energy-rich pyrites and other reduced sulfur compounds present in mine tailing heaps and in exposed rock faces is metabolized to form sulfates, thereby forming potentially toxic sulfuric acid
. Acid mine drainage drastically alters the acidity and chemistry of groundwater and streams, and may endanger plant and animal populations. Activities similar to acid mine drainage, but on a much lower scale, are also found in natural conditions such as the rocky beds of glaciers, in soil and talus, on stone monuments and buildings and in the deep subsurface.
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
that uses an inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
(e.g., carbon dioxide fixation) or energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
conservation via aerobic or anaerobic respiration
Cellular respiration
Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products. The reactions involved in respiration are catabolic reactions that involve...
. Known chemolithotrophs are exclusively microbes; No known macrofauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
possesses the ability to utilize inorganic compounds as energy sources. Macrofauna and lithotrophs can form symbiotic relationships, in which case the lithotrophs are called "prokaryotic symbionts." An example of this is chemolithotrophic bacteria in deep sea worms or plastids, which are organelles within plant cells that may have evolved from photolithotrophic cyanobacteria-like organisms. Lithotrophs belong to either 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...
or the domain Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...
. The term "Lithotroph" is created from the terms 'lithos' (rock) and 'troph' (consumer), meaning the "eaters of rock." Many lithoautotrophs are extremophiles, but this is not universally so.
Different from a lithotroph is an organotroph
Organotroph
An organotroph is an organism that obtains hydrogen or electrons from organic substrates . Antonym: Lithotroph- See also :* Lithotroph* Heterotroph* Primary nutritional groups...
, an organism which gets its reducing agents from the catabolism
Catabolism
Catabolism is the set of metabolic pathways that break down molecules into smaller units and release energy. In catabolism, large molecules such as polysaccharides, lipids, nucleic acids and proteins are broken down into smaller units such as monosaccharides, fatty acids, nucleotides, and amino...
of organic compounds.
Biochemistry
Lithotrophs consume reducedRedox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
compounds (rich in electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s).
Chemolithotrophs
In chemolithotrophs, the compounds - the electron donorElectron donor
An electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process....
s - are oxidized in the cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
, and the electrons are channeled into respiratory chains, ultimately producing ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
. The electron acceptor can be oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
(in aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...
bacteria), but a variety of other electron acceptors, organic
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
and inorganic, are also used by various species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. Unlike water, the hydrogen compounds used in chemosynthesis are high in energy. Other lithotrophs are able to directly utilize inorganic substances, e.g., iron, hydrogen sulfide, elemental sulfur, or thiosulfate, for some or all of their energy needs.
Here are a few examples of chemolithotrophic pathways, any of which may use oxygen, sulfur or other molecules as electron acceptors:
| Name | Examples | Source of energy and electrons | Respiration electron acceptor |
|---|---|---|---|
| Iron bacteria Iron bacteria In the management of water-supply wells, iron bacteria are bacteria that derive the energy they need to live and multiply by oxidizing dissolved ferrous iron . The resulting ferric oxide is insoluble, and appears as brown gelatinous slime that will stain plumbing fixtures, and clothing or utensils... |
Acidithiobacillus ferrooxidans | Fe2+ (ferrous Ferrous Ferrous , in chemistry, indicates a divalent iron compound , as opposed to ferric, which indicates a trivalent iron compound .... iron) → Fe3+ (ferric Ferric Ferric refers to iron-containing materials or compounds. In chemistry the term is reserved for iron with an oxidation number of +3, also denoted iron or Fe3+. On the other hand, ferrous refers to iron with oxidation number of +2, denoted iron or Fe2+... iron) + e- |
O (oxygen) → HO (water) |
| Nitrosifying bacteria | Nitrosomonas Nitrosomonas Nitrosomonas is a genus comprising rod shaped chemoautotrophic bacteria.This rare bacteria oxidizes ammonia into nitrite as a metabolic process. Nitrosomonas are useful in treatment of industrial and sewage waste and in the process of bioremediation. They are important in the nitrogen cycle by... |
NH3 (ammonia Ammonia Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or... ) → NO (nitrite Nitrite The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent... ) + e- |
O (oxygen) → HO (water) |
| Nitrifying bacteria Nitrifying bacteria Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera bacteria that grow by consuming inorganic nitrogen compounds... |
Nitrobacter Nitrobacter Nitrobacter is genus of mostly rod-shaped, gram-negative, and chemoautotrophic bacteria.Nitrobacter plays an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil... |
NO (nitrite) → NO (nitrate Nitrate The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a... ) + e- |
O (oxygen) → HO (water) |
| Chemotrophic purple sulfur bacteria Purple sulfur bacteria The purple sulfur bacteria are a group of Proteobacteria capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in hot springs or stagnant water. Unlike plants, algae, and cyanobacteria, they do not use water as their... |
Halothiobacillaceae | S (sulfide Sulfide A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :... ) → S (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... ) + e- |
O (oxygen) → HO (water) |
| Sulfur-oxidizing bacteria | Chemotrophic Rhodobacteraceae Rhodobacteraceae The Rhodobacteraceae are a family of proteobacteria, given their own order within the alpha subgroup. Like all proteobaceria, they are gram-negative. It contains chemoorganotrophs and photoheterotrophs bacteria. Many occur in aquatic habitats.... and Thiotrichaceae Thiotrichaceae The Thiotrichaceae are a family of Proteobacteria, including Thiomargarita namibiensis, the largest known bacterium.... |
S (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... ) → SO (sulfate Sulfate In inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:... ) + e- |
O (oxygen) → HO (water) |
| Aerobic Aerobic Aerobic is a word that means "requiring air", where "air" usually means oxygen.Aerobic may also refer to:* Aerobic exercise, prolonged exercise of moderate intensity* Aerobics, a form of aerobic exercise... hydrogen bacteria |
Cupriavidus metallidurans Cupriavidus metallidurans Cupriavidus metallidurans strain CH34, is a non-spore-forming bacillus which is adapted to survive several forms of heavy metal stress. Therefore, it is an ideal subject to study heavy metal disturbance of cellular processes... |
H2 (hydrogen Hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly... ) → H2O (water Water Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a... ) + e- |
O (oxygen) → HO (water) |
| Anammox Anammox Anammox, an abbreviation for ANaerobic AMMonium OXidation, is a globally important microbial process of the nitrogen cycle . The bacteria mediating this process were identified in 1991, and at the time were a great surprise for the scientific community... bacteria |
Planctomycetes Planctomycetes Planctomycetes are a phylum of aquatic bacteria and are found in samples of brackish, and marine and fresh water. They reproduce by budding. In structure, the organisms of this group are ovoid and have a holdfast, called the stalk, at the nonreproductive end that helps them to attach to each other... |
NH3 (ammonia Ammonia Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or... ) → N (nitrogen) + e- |
NO (nitrite) |
| Thiobacillus denitrificans | Thiobacillus denitrificans | S (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... ) → SO (sulfate) + e- |
NO (nitrate) |
| Sulfate-reducing bacteria Sulfate-reducing bacteria Sulfate-reducing bacteria are those bacteria and archaea that can obtain energy by oxidizing organic compounds or molecular hydrogen while reducing sulfate to hydrogen sulfide... : Hydrogen bacteria |
H2 (hydrogen Hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly... ) → H2O (water Water Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a... ) + e- |
Sulfate (SO) | |
| Sulfate-reducing bacteria Sulfate-reducing bacteria Sulfate-reducing bacteria are those bacteria and archaea that can obtain energy by oxidizing organic compounds or molecular hydrogen while reducing sulfate to hydrogen sulfide... : Phosphite bacteria |
Desulfotignum phosphitoxidans | PO (phosphite Phosphite A phosphite is a salt of phosphorous acid. The phosphite ion is a polyatomic ion with a phosphorus central atom where phosphorus has an oxidation state of +3... ) → PO (phosphate Phosphate A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in... ) + e- |
Sulfate (SO) |
| Methanogens | Archaea Archaea The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon... |
H2 (hydrogen Hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly... ) → H2O (water Water Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a... ) + e- |
CO2 (carbon dioxide Carbon dioxide Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom... ) |
| Carboxydotrophic bacteria | Carboxydothermus hydrogenoformans Carboxydothermus hydrogenoformans Carboxydothermus hydrogenoformans is an extremely thermophilic anaerobic Gram-positive bacterium that has the interesting property of producing hydrogen as a waste product while feeding on carbon monoxide and water.... |
carbon monoxide Carbon monoxide Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal... (CO) → carbon dioxide Carbon dioxide Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom... (CO2) + e- |
HO (water) → H (hydrogen) |
Photolithotrophs
Photolithotrophs obtain energy from light and therefore use inorganic electron donors only to fuel biosynthetic reactions (e. g., carbon dioxide fixation in lithoautotrophs). (See navigation box below)Lithoheterotrophs versus lithoautotrophs
Lithotrophic bacteria cannot use, of course, their inorganic energy source as a carbonCarbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
source for the synthesis of their cells. They choose one of three options:
- Lithoheterotrophs do not have the possibility to fix carbon dioxideCarbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and must consume additional organic compounds in order to break them apart and use their carbon. Only few bacteria are fully heterolithotrophic. - LithoautotrophLithoautotrophA lithoautotroph is a microbe which derives energy from reduced compounds of mineral origin. They may also be referred to as chemolithoautotrophs, a type of lithotrophs, reflecting their autotrophic metabolic pathways. Lithoautotrophs are exclusively microbes; macrofauna do not possess the...
s are able to use carbon dioxideCarbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
from the air as carbon source, the same way plantPlantPlants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s do. - MixotrophMixotrophA mixotroph is a microorganism that can use a mix of different sources of energy and carbon. Possible are alternations between photo- and chemotrophy, between litho- and organotrophy, between auto- and heterotrophy or a combination of it...
s will take up and utilise organic material to complement their carbon dioxide fixation source (mix between autotrophy and heterotrophy). Many lithotrophs are recognised as mixotrophic in regard of their C-metabolism.
Chemolithotrophs versus photolithotrophs
In addition to this division, lithotrophs differ in the initial energy source which initiates ATP production:- Chemolithotrophs use the above-mentioned inorganic compounds for aerobic or anaerobic respiration. The energy produced by the oxidation of these compounds is enough for ATP production. Some of the electrons derived from the inorganic donors also need to be channeled into biosynthesis. Mostly, additional energy has to be invested to transform these reducing equivalents to the forms and redox potentials needed (mostly NADH or NADPH), which occurs by reverse electron transfer reactions.
- Photolithotrophs use lightLightLight or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
as energy source. These bacteria are photosyntheticPhotosynthesisPhotosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
; photolithotrophic bacteria are found in the purple bacteriaPurple bacteriaPurple bacteria or purple photosynthetic bacteria are proteobacteria that are phototrophic, that is capable of producing energy through photosynthesis...
(e. g., ChromatiaceaeChromatiaceaeThe Chromatiaceae are the main family of purple sulfur bacteria. They are distinguished by producing sulfur globules within their cells. These are an intermediate in the oxidization of sulfide, which is ultimately converted into sulfate, and may serve as a reserve. Members are found in both...
), green bacteria (Chlorobiaceae and ChloroflexiChloroflexiChloroflexi is one of four classes of bacteria in the phylum Chloroflexi, known as filamentous green non-sulfur bacteria. They produce energy from light and are named for their green pigment, usually found in photosynthetic bodies called chlorosomes....
) and Cyanobacteria. The electrons obtained from the electron donors (purple and green bacteria oxidize sulfide, sulfur, sulfite, iron or hydrogen; cyanobacteria extract reducing equivalents from water, i. e., oxidise water to oxygen) are not used for ATP production (as long as there is light); they are used in biosynthetic reactions. Some photolithotrophs shift over to chemolithotrophic metabolism in the dark.
Geological significance
Lithotrophs participate in many geological processes, such as the weathering of parent material (bedrock) to form soil, as well as biogeochemical cycling of sulfurSulfur
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...
, nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, and other elements
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
. They may be present in the deep terrestrial subsurface (they have been found well over 3 km 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, lithotrophs play a critical role in the maintenance of life on Earth.
Lithotrophic 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 pyrites and other reduced sulfur compounds present in mine tailing heaps and in exposed rock faces is metabolized to form sulfates, thereby forming 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...
. Acid mine drainage drastically alters the acidity and chemistry of groundwater and streams, and may endanger plant and animal populations. Activities similar to acid mine drainage, but on a much lower scale, are also found in natural conditions such as the rocky beds of glaciers, in soil and talus, on stone monuments and buildings and in the deep subsurface.