Decomposition

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Decomposition of strawberries played backwards.
A rotten apple after it fell from a tree Rotten apple under the tree.jpg
A rotten apple after it fell from a tree
Decomposing fallen nurse log in a forest Berge naturreservat omkullfallet liten tall.jpg
Decomposing fallen nurse log in a forest

Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere. Bodies of living organisms begin to decompose shortly after death. Animals, such as earthworms, also help decompose the organic materials. Organisms that do this are known as decomposers or detritivores. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy from the Greek word taphos, meaning tomb. Decomposition can also be a gradual process for organisms that have extended periods of dormancy. [1]

Contents

One can differentiate abiotic decomposition from biotic decomposition (biodegradation). The former means "the degradation of a substance by chemical or physical processes", e.g., hydrolysis; the latter means "the metabolic breakdown of materials into simpler components by living organisms", [2] typically by microorganisms.

Animal decomposition

Ants eating a dead snake Ants cleaning dead snake.jpg
Ants eating a dead snake

Decomposition begins at the moment of death, caused by two factors: autolysis, the breaking down of tissues by the body's own internal chemicals and enzymes, and putrefaction, the breakdown of tissues by bacteria. These processes release compounds such as cadaverine and putrescine, that are the chief source of the unmistakably putrid odor of decaying animal tissue. [3]

Prime decomposers are bacteria or fungi, though larger scavengers also play an important role in decomposition if the body is accessible to insects, mites and other animals. Additionally, [4] soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. The most important arthropods that are involved in the process include carrion beetles, mites, [5] [6] the flesh-flies (Sarcophagidae) and blow-flies (Calliphoridae), such as the green bottle flies seen in the summer. In North America, the most important non-insect animals that are typically involved in the process include mammal and bird scavengers, such as coyotes, dogs, wolves, foxes, rats, crows and vultures. [7] Some of these scavengers also remove and scatter bones, which they ingest at a later time. Aquatic and marine environments have break-down agents that include bacteria, fish, crustaceans, fly larvae [8] and other carrion scavengers.

Stages of decomposition

Five general stages are typically used to describe the process of decomposition in vertebrate animals: fresh, bloat, active decay, advanced decay, and dry/remains. [9] The general stages of decomposition are coupled with two stages of chemical decomposition: autolysis and putrefaction. [10] These two stages contribute to the chemical process of decomposition, which breaks down the main components of the body. With death the microbiome of the living organism collapses and is followed by the necrobiome that undergoes predictable changes over time. [11]

Fresh

Among those animals that have a heart, the fresh stage begins immediately after the heart stops beating. From the moment of death, the body begins cooling or warming to match the temperature of the ambient environment, during a stage called algor mortis. Shortly after death, within three to six hours, the muscular tissues become rigid and incapable of relaxing, during a stage called rigor mortis. Since blood is no longer being pumped through the body, gravity causes it to drain to the dependent portions of the body, creating an overall bluish-purple discoloration termed livor mortis or, more commonly, lividity. Depending on the position of the body, these parts would vary. For instance, if the person was flat on their back when they died, the blood would collect in the parts that are touching the ground. If the person was hanging, it would collect in their fingertips, toes and earlobes. [12]

Once the heart stops, the blood can no longer supply oxygen or remove carbon dioxide from the tissues. The resulting decrease in pH and other chemical changes cause cells to lose their structural integrity, bringing about the release of cellular enzymes capable of initiating the breakdown of surrounding cells and tissues. This process is known as autolysis. [13]

Visible changes caused by decomposition are limited during the fresh stage, although autolysis may cause blisters to appear at the surface of the skin. [14]

The small amount of oxygen remaining in the body is quickly depleted by cellular metabolism and aerobic microbes naturally present in respiratory and gastrointestinal tracts, creating an ideal environment for the proliferation of anaerobic organisms. These multiply, consuming the body's carbohydrates, lipids and proteins, to produce a variety of substances including propionic acid, lactic acid, methane, hydrogen sulfide and ammonia. The process of microbial proliferation within a body is referred to as putrefaction and leads to the second stage of decomposition known as bloat. [15]

Blowflies and flesh flies are the first carrion insects to arrive and they seek a suitable oviposition site. [9]

Bloat

The bloat stage provides the first clear visual sign that microbial proliferation is underway. In this stage, anaerobic metabolism takes place, leading to the accumulation of gases, such as hydrogen sulfide, carbon dioxide, methane and nitrogen. The accumulation of gases within the bodily cavity causes the distention of the abdomen and gives a cadaver its overall bloated appearance. [16] The gases produced also cause natural liquids and liquefying tissues to become frothy. [17] As the pressure of the gases within the body increases, fluids are forced to escape from natural orifices, such as the nose, mouth and anus, and enter the surrounding environment. The buildup of pressure combined with the loss of integrity of the skin may also cause the body to rupture. [16]

Intestinal anaerobic bacteria transform haemoglobin into sulfhemoglobin and other colored pigments. The associated gases which accumulate within the body at this time aid in the transport of sulfhemoglobin throughout the body via the circulatory and lymphatic systems, giving the body an overall marbled appearance. [18]

If insects have access, maggots hatch and begin to feed on the body's tissues. [9] Maggot activity, typically confined to natural orifices, and masses under the skin, causes the skin to slip, and hair to detach from the skin. [17] Maggot feeding, and the accumulation of gases within the body, eventually leads to post-mortem skin ruptures which will then further allow purging of gases and fluids into the surrounding environment. [15] Ruptures in the skin allow oxygen to re-enter the body and provide more surface area for the development of fly larvae and the activity of aerobic microorganisms. [16] The purging of gases and fluids results in the strong distinctive odors associated with decay. [9]

Active decay

Active decay is characterized by the period of greatest mass loss. This loss occurs as a result of both the voracious feeding of maggots and the purging of decomposition fluids into the surrounding environment. [16] The purged fluids accumulate around the body and create a cadaver decomposition island (CDI). [19] Liquefaction of tissues and disintegration become apparent during this time and strong odors persist. [9] The end of active decay is signaled by the migration of maggots away from the body to pupate. [15]

Advanced decay

Decomposition is largely inhibited during advanced decay due to the loss of readily available cadaveric material. [16] Insect activity is also reduced during this stage. [17] When the carcass is located on soil, the area surrounding it will show evidence of vegetation death. [16] The CDI surrounding the carcass will display an increase in soil carbon and nutrients such as phosphorus, potassium, calcium and magnesium; [15] changes in pH; and a significant increase in soil nitrogen. [20]

Dry/remains

As the ecosystem recovers from the disturbance, the CDI moves into the dry/remains stage, which is characterized by a decrease in the intensity of the disturbance and an increase in the amount of plant growth around the affected area. This is a sign that the nutrients and other ecological resources present in the surrounding soil have not yet returned to their normal levels.

During this stage, it is important to monitor the ecosystem for any signs of continued disturbance or ecological stress. The resurgence of plant growth is a positive sign, but it may take several years for the ecosystem to fully recover and return to its pre-disturbance state. [16] All that remains of the cadaver at this stage is dry skin, cartilage, and bones, [9] which will become dry and bleached if exposed to the elements. [17] If all soft tissue is removed from the cadaver, it is referred to as completely skeletonized, but if only portions of the bones are exposed, it is referred to as partially skeletonized. [21]

Pig carcass in the different stages of decomposition: fresh, bloat, active decay, advanced decay and dry remains Decomposition stages.jpg
Pig carcass in the different stages of decomposition: fresh, bloat, active decay, advanced decay and dry remains

Factors affecting decomposition of bodies

Exposure to the elements

A dead body that has been exposed to the open elements, such as water and air, will decompose more quickly and attract much more insect activity than a body that is buried [22] or confined in special protective gear or artifacts. [23] This is due, in part, to the limited number of insects that can penetrate soil [24] and the lower temperatures under the soil. [25]

The rate and manner of decomposition in an animal body are strongly affected by several factors. In roughly descending degrees of importance, [26] they are:

The speed at which decomposition occurs varies greatly. Factors such as temperature, humidity, and the season of death all determine how fast a fresh body will skeletonize or mummify. A basic guide for the effect of environment on decomposition is given as Casper's Law (or Ratio): if all other factors are equal, then, when there is free access of air a body decomposes twice as fast as if immersed in water and eight times faster than if buried in the earth. Ultimately, the rate of bacterial decomposition acting on the tissue will depend upon the temperature of the surroundings. Colder temperatures decrease the rate of decomposition while warmer temperatures increase it. A dry body will not decompose efficiently. Moisture helps the growth of microorganisms that decompose the organic matter, but too much moisture could lead to anaerobic conditions slowing down the decomposition process. [27]

The most important variable is the body's accessibility to insects, particularly flies. On the surface in tropical areas, invertebrates alone can easily reduce a fully fleshed corpse to clean bones in under two weeks. [28] The skeleton itself is not permanent; acids in soils can reduce it to unrecognizable components. [29] This is one reason given for the lack of human remains found in the wreckage of the Titanic, even in parts of the ship considered inaccessible to scavengers. [30] Freshly skeletonized bone is often called green bone and has a characteristic greasy feel. [31] Under certain conditions (underwater, but also cool, damp soil), bodies may undergo saponification and develop a waxy substance called adipocere, caused by the action of soil chemicals on the body's proteins and fats. The formation of adipocere slows decomposition by inhibiting the bacteria that cause putrefaction. [32]

In extremely dry or cold conditions, the normal process of decomposition is halted – by either lack of moisture or temperature controls on bacterial and enzymatic action – causing the body to be preserved as a mummy. Frozen mummies commonly restart the decomposition process when thawed (see Ötzi the Iceman), whilst heat-desiccated mummies remain so unless exposed to moisture. [33]

The bodies of newborns who never ingested food are an important exception to the normal process of decomposition. They lack the internal microbial flora that produces much of decomposition [34] and quite commonly mummify if kept in even moderately dry conditions. [35]

Anaerobic vs aerobic

Aerobic decomposition takes place in the presence of oxygen. This is most common to occur in nature. Living organisms that use oxygen to survive feed on the body. Anaerobic decomposition takes place in the absence of oxygen. This could be a place where the body is buried in organic material and oxygen cannot reach it. This process of putrefaction has a bad odor accompanied by it due to the hydrogen sulfide and organic matter containing sulfur. [36]

Artificial preservation

Embalming is the practice of delaying the decomposition of human and animal remains. Embalming slows decomposition somewhat but does not forestall it indefinitely. Embalmers typically pay great attention to parts of the body seen by mourners, such as the face and hands. The chemicals used in embalming repel most insects and slow down bacterial putrefaction by either killing existing bacteria in or on the body themselves [37] or by fixing cellular proteins, which means that they cannot act as a nutrient source for subsequent bacterial infections. [38] In sufficiently dry environments, an embalmed body may end up mummified and it is not uncommon for bodies to remain preserved to a viewable extent after decades. [39] Notable viewable embalmed bodies include those of:

Environmental preservation

A body buried in a sufficiently dry environment may be well preserved for decades. This was observed in the case for murdered civil rights activist Medgar Evers, who was found to be almost perfectly preserved over 30 years after his death, permitting an accurate autopsy when the case of his murder was re-opened in the 1990s. [43]


Bodies submerged in a peat bog may become naturally embalmed, arresting decomposition and resulting in a preserved specimen known as a bog body. The generally cool and anoxic conditions in these environments limits the rate of microbial activity, thus limiting the potential for decomposition. [44] The time for an embalmed body to be reduced to a skeleton varies greatly. Even when a body is decomposed, embalming treatment can still be achieved (the arterial system decays more slowly) but would not restore a natural appearance without extensive reconstruction and cosmetic work, and is largely used to control the foul odors due to decomposition. [38]

An animal can be preserved almost perfectly, for millions of years in a resin such as amber. [45]

There are some examples where bodies have been inexplicably preserved (with no human intervention) for decades or centuries and appear almost the same as when they died. In some religious groups, this is known as incorruptibility. It is not known whether or for how long a body can stay free of decay without artificial preservation. [46]

Importance to forensic sciences

Various sciences study the decomposition of bodies under the general rubric of forensic science because the usual motive for such studies is to determine the time and cause of death for legal purposes:

The University of Tennessee Anthropological Research Facility (better known as the Body Farm) in Knoxville, Tennessee, has several bodies laid out in various situations in a fenced-in plot near the medical center. Scientists at the Body Farm study how the human body decays in various circumstances to gain a better understanding of decomposition.

Plant decomposition

A decaying peach over a period of six days. Each frame is approximately 12 hours apart, as the fruit shrivels and becomes covered with mold. DecayingPeachSmall.gif
A decaying peach over a period of six days. Each frame is approximately 12 hours apart, as the fruit shrivels and becomes covered with mold.

Decomposition of plant matter occurs in many stages. It begins with leaching by water; the most easily lost and soluble carbon compounds are liberated in this process. Another early process is physical breakup or fragmentation of the plant material into smaller pieces, providing greater surface area for microbial colonization and attack. In smaller dead plants, this process is largely carried out by the soil invertebrate fauna, [51] [52] whereas in larger plants, primarily parasitic life-forms such as insects and fungi play a major role in breaking down matter, and are not assisted[ clarification needed ] by numerous detritivore species.

Following this, the plant detritus (consisting of cellulose, hemicellulose, microbial products, and lignin) undergoes chemical alteration by microbes. Different types of compounds decompose at different rates. This is dependent on their chemical structure. For instance, lignin is a component of wood, which is relatively resistant to decomposition and can in fact only be decomposed by certain fungi, such as the white-rot fungi.

Wood decomposition is a complex process involving fungi which transport nutrients to the nutritionally scarce wood from outside environment. [53] Because of this nutritional enrichment, the fauna of saproxylic insects may develop [54] and, in turn, affect dead wood, contributing to decomposition and nutrient cycling in the forest floor. [54] Lignin is one such remaining product of decomposing plants with a very complex chemical structure, causing the rate of microbial breakdown to slow. Warmth increases the speed of plant decay by roughly the same amount, regardless of the composition of the plant. [55]

In most grassland ecosystems, natural damage from fire, insects that feed on decaying matter, termites, grazing mammals, and the physical movement of animals through the grass are the primary agents of breakdown and nutrient cycling, while bacteria and fungi play the main roles in further decomposition.

The chemical aspects of plant decomposition always involve the release of carbon dioxide. In fact, decomposition contributes over 90 percent of carbon dioxide released each year. [55]

Food decomposition

A punnet of rotten peaches A punnet of rotten peaches.jpg
A punnet of rotten peaches

The decomposition of food, either plant or animal, called spoilage in this context, is an important field of study within food science. Food decomposition can be slowed down by conservation. The spoilage of meat occurs, if the meat is untreated, in a matter of hours or days and results in the meat becoming unappetizing, poisonous or infectious. Spoilage is caused by the practically unavoidable infection and subsequent decomposition of meat by bacteria and fungi, which are borne by the animal itself, by the people handling the meat, and by their implements. Meat can be kept edible for a much longer time – though not indefinitely – if proper hygiene is observed during production and processing, and if appropriate food safety, food preservation and food storage procedures are applied.

Spoilage of food is attributed to contamination from microorganisms such as bacteria, molds and yeasts, along with natural decay of the food. [56] These decomposition bacteria reproduce at rapid rates under conditions of moisture and preferred temperatures. When the proper conditions are lacking the bacteria may form spores which lurk until suitable conditions arise to continue reproduction. [56]

Rate of decomposition

The rate of decomposition is governed by three sets of factors—the physical environment (temperature, moisture and soil properties), the quantity and quality of the dead material available to decomposers, and the nature of the microbial community itself. [57]

Decomposition rates are low under very wet or very dry conditions. Decomposition rates are highest in damp, moist conditions with adequate levels of oxygen. Wet soils tend to become deficient in oxygen (this is especially true in wetlands), which slows microbial growth. In dry soils, decomposition slows as well, but bacteria continue to grow (albeit at a slower rate) even after soils become too dry to support plant growth. When the rains return and soils become wet, the osmotic gradient between the bacterial cells and the soil water causes the cells to gain water quickly. Under these conditions, many bacterial cells burst, releasing a pulse of nutrients. [57] Decomposition rates also tend to be slower in acidic soils. [57] Soils which are rich in clay minerals tend to have lower decomposition rates, and thus, higher levels of organic matter. [57] The smaller particles of clay result in a larger surface area that can hold water. The higher the water content of a soil, the lower the oxygen content [58] and consequently, the lower the rate of decomposition. Clay minerals also bind particles of organic material to their surface, making them less accessible to microbes. [57] Soil disturbance like tilling increases decomposition by increasing the amount of oxygen in the soil and by exposing new organic matter to soil microbes. [57]

The quality and quantity of the material available to decomposers is another major factor that influences the rate of decomposition. Substances like sugars and amino acids decompose readily and are considered labile. Cellulose and hemicellulose, which are broken down more slowly, are "moderately labile". Compounds which are more resistant to decay, like lignin or cutin, are considered recalcitrant. [57] Litter with a higher proportion of labile compounds decomposes much more rapidly than does litter with a higher proportion of recalcitrant material. Consequently, dead animals decompose more rapidly than dead leaves, which themselves decompose more rapidly than fallen branches. [57] As organic material in the soil ages, its quality decreases. The more labile compounds decompose quickly, leaving an increasing proportion of recalcitrant material. Microbial cell walls also contain recalcitrant materials like chitin, and these also accumulate as the microbes die, further reducing the quality of older soil organic matter. [57]

See also

Related Research Articles

<span class="mw-page-title-main">Forensic entomology</span> Application of insect and other arthropod biology to forensics

Forensic entomology is an science study of colonization of a dead body by arthropods. This includes the study of insect types commonly associated with cadavers, their respective life cycles, their ecological presences in a given environment, as well as the changes in insect assemblage with the progression of decomposition. Insect succession patterns are identified based on the time a given species of insect spends in a given developmental stage, and how many generations have been produced since the insects introduction to a given food source. Insect development alongside environmental data such as temperature and vapor density, can be used to estimate the time since death, due to the fact that flying insects are attracted to a body immediately after death. The identification of postmortem interval to aid in death investigations is the primary scope of this scientific field. However, forensic entomology is not limited to homicides, it has also been used in cases of neglect and abuse, in toxicology contexts to detect the presence of drugs, and in dry shelf food contamination incidents. Equally, insect assemblages present on a body, can be used to approximate a given location, as certain insects may be unique to certain areas. Therefore, forensic entomology can be divided into three subfields: urban, stored-product and medico-legal/medico-criminal entomology.

<span class="mw-page-title-main">Taphonomy</span> Study of decomposition and fossilization of organisms

Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term taphonomy was introduced to paleontology in 1940 by Soviet scientist Ivan Efremov to describe the study of the transition of remains, parts, or products of organisms from the biosphere to the lithosphere.

Putrefaction is the fifth stage of death, following pallor mortis, livor mortis, algor mortis, and rigor mortis. This process references the breaking down of a body of an animal post-mortem. In broad terms, it can be viewed as the decomposition of proteins, and the eventual breakdown of the cohesiveness between tissues, and the liquefaction of most organs. This is caused by the decomposition of organic matter by bacterial or fungal digestion, which causes the release of gases that infiltrate the body's tissues, and leads to the deterioration of the tissues and organs. The approximate time it takes putrefaction to occur is dependent on various factors. Internal factors that affect the rate of putrefaction include the age at which death has occurred, the overall structure and condition of the body, the cause of death, and external injuries arising before or after death. External factors include environmental temperature, moisture and air exposure, clothing, burial factors, and light exposure. Body farms are facilities that study the way various factors affect the putrefaction process.

Coffin birth, also known as postmortem fetal extrusion, is the expulsion of a nonviable fetus through the vaginal opening of the decomposing body of a deceased pregnant woman due to increasing pressure from intra-abdominal gases. This kind of postmortem delivery occurs very rarely during the decomposition of a body. The practice of chemical preservation, whereby chemical preservatives and disinfectant solutions are pumped into a body to replace natural body fluids, have made the occurrence of "coffin birth" so rare that the topic is rarely mentioned in international medical discourse.

<span class="mw-page-title-main">Detritivore</span> Animal that feeds on decomposing plant and animal parts as well as faeces

Detritivores are heterotrophs that obtain nutrients by consuming detritus. There are many kinds of invertebrates, vertebrates, and plants that carry out coprophagy. By doing so, all these detritivores contribute to decomposition and the nutrient cycles. Detritivores should be distinguished from other decomposers, such as many species of bacteria, fungi and protists, which are unable to ingest discrete lumps of matter. Instead, these other decomposers live by absorbing and metabolizing on a molecular scale. The terms detritivore and decomposer are often used interchangeably, but they describe different organisms. Detritivores are usually arthropods and help in the process of remineralization. Detritivores perform the first stage of remineralization, by fragmenting the dead plant matter, allowing decomposers to perform the second stage of remineralization.

<span class="mw-page-title-main">Post-mortem interval</span> Time that has elapsed since a person has died

The post-mortem interval (PMI) is the time that has elapsed since an individual's death. When the time of death is not known, the interval may be estimated, and so an approximate time of death established. Postmortem interval estimations can range from hours, to days or even years depending on the type of evidence present. There are standard medical and scientific techniques supporting such an estimation.

The pedosphere is the outermost layer of the Earth that is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, atmosphere, hydrosphere and biosphere. The pedosphere is the skin of the Earth and only develops when there is a dynamic interaction between the atmosphere, biosphere, lithosphere and the hydrosphere. The pedosphere is the foundation of terrestrial life on Earth.

Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come from the feces and remains of organisms such as plants and animals. Organic molecules can also be made by chemical reactions that do not involve life. Basic structures are created from cellulose, tannin, cutin, and lignin, along with other various proteins, lipids, and carbohydrates. Organic matter is very important in the movement of nutrients in the environment and plays a role in water retention on the surface of the planet.

<span class="mw-page-title-main">Soil biology</span> Study of living things in soil

Soil biology is the study of microbial and faunal activity and ecology in soil. Soil life, soil biota, soil fauna, or edaphon is a collective term that encompasses all organisms that spend a significant portion of their life cycle within a soil profile, or at the soil-litter interface. These organisms include earthworms, nematodes, protozoa, fungi, bacteria, different arthropods, as well as some reptiles, and species of burrowing mammals like gophers, moles and prairie dogs. Soil biology plays a vital role in determining many soil characteristics. The decomposition of organic matter by soil organisms has an immense influence on soil fertility, plant growth, soil structure, and carbon storage. As a relatively new science, much remains unknown about soil biology and its effect on soil ecosystems.

<span class="mw-page-title-main">Phosphorus cycle</span> Biogeochemical movement

The phosphorus cycle is the biogeochemical cycle that involves the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and phosphorus-based materials do not enter the gaseous phase readily. The production of phosphine gas occurs in isolated and specific conditions. Therefore, the phosphorus cycle is primarily examined studying the movement of orthophosphate (PO4)3-, the form of phosphorus that is most commonly seen in the environment, through terrestrial and aquatic ecosystems.

<span class="mw-page-title-main">Cadaver</span> Dead human body

A cadaver or corpse is a dead human body. Cadavers are used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Students in medical school study and dissect cadavers as a part of their education. Others who study cadavers include archaeologists and arts students. In addition, a cadaver may be used in the development and evaluation of surgical instruments.

Forensic entomological decomposition is how insects decompose and what that means for timing and information in criminal investigations. Medicolegal entomology is a branch of forensic entomology that applies the study of insects to criminal investigations, and is commonly used in death investigations for estimating the post-mortem interval (PMI). One method of obtaining this estimate uses the time and pattern of arthropod colonization. This method will provide an estimation of the period of insect activity, which may or may not correlate exactly with the time of death. While insect successional data may not provide as accurate an estimate during the early stages of decomposition as developmental data, it is applicable for later decompositional stages and can be accurate for periods up to a few years.

<span class="mw-page-title-main">Microbial mat</span> Multi-layered sheet of microorganisms

A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, or bacteria alone. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in deserts. A few are found as endosymbionts of animals.

<span class="mw-page-title-main">Microbiology of decomposition</span>

Microbiology of decomposition is the study of all microorganisms involved in decomposition, the chemical and physical processes during which organic matter is broken down and reduced to its original elements.

Decomposition in animals is a process that begins immediately after death and involves the destruction of soft tissue, leaving behind skeletonized remains. The chemical process of decomposition is complex and involves the breakdown of soft tissue, as the body passes through the sequential stages of decomposition. Autolysis and putrefaction also play major roles in the disintegration of cells and tissues.

The smell of death is a smell occurring during decomposition. It is made up of over 800 different chemicals. There have been efforts to synthesize the smell of death. It has also been used as evidence in court trials involving murder.

The necrobiome has been defined as the community of species associated with decaying corpse remains. The process of decomposition is complex. Microbes decompose cadavers, but other organisms including fungi, nematodes, insects, and larger scavenger animals also contribute. Once the immune system is no longer active, microbes colonizing the intestines and lungs decompose their respective tissues and then travel throughout the body via the blood and lymphatic systems to break down other tissue and bone. During this process, gases are released as a by-product and accumulate, causing bloating. Eventually, the gases seep through the body's wounds and natural openings, providing a way for some microbes to exit from the inside of the cadaver and inhabit the outside. The microbial communities colonizing the internal organs of a cadaver are referred to as the thanatomicrobiome. The region outside of the cadaver that is exposed to the external environment is referred to as the epinecrotic portion of the necrobiome, and is especially important when determining the time and location of death for an individual. Different microbes play specific roles during each stage of the decomposition process. The microbes that will colonize the cadaver and the rate of their activity are determined by the cadaver itself and the cadaver's surrounding environmental conditions.

<span class="mw-page-title-main">Corpse decomposition</span> Process in which animal bodies break down

Decomposition is the process in which the organs and complex molecules of animal and human bodies break down into simple organic matter over time. In vertebrates, five stages of decomposition are typically recognized: fresh, bloat, active decay, advanced decay, and dry/skeletonized. Knowing the different stages of decomposition can help investigators in determining the post-mortem interval (PMI). The rate of decomposition of human remains can vary due to environmental factors and other factors. Environmental factors include temperature, burning, humidity, and the availability of oxygen. Other factors include body size, clothing, and the cause of death.

The stages of death of a human being have medical, biochemical and legal aspects. The term taphonomy from palaeontology applies to the fate of all kinds of remains of organisms. Forensic taphonomy is concerned with remains of the human body.

<i>Necrodes littoralis</i> Species of beetle

Necrodes littoralis, also known as the short sexton beetle, is a species of carrion beetle of the genus Necrodes, found in countries across Europe. As a carrion beetle, it feeds on decaying vertebrate remains and maggots. This species' feeding behaviors make it an important asset to forensic entomology.

References

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