''Mucor plumbeus'' is a

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

in the family

Mucoraceae The Mucoraceae are a family of fungi of the order Mucorales, characterized by having the thallus not segmented or ramified. Pathogenic genera include ''Absidia'', '' Apophysomyces'', '' Mucor'', '' Rhizomucor'', and '' Rhizopus''. According to a ...

(subphylum

Mucoromycotina Mucoromycotina is a subphylum of uncertain placement in Fungi. It was considered part of the phylum Zygomycota, but recent phylogenetic studies have shown that it was polyphyletic and thus split into several groups, it is now thought to be a para ...

) that is very common, abundant and distributed worldwide. ''Mucor plumbeus'' is not known to be a plant or animal pathogen; however it is able to elicit an

immune response An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellula ...

in humans by activating the

complement system The complement system, also known as complement cascade, is a part of the humoral, innate immune system and enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inf ...

. This species is commonly found in various types of soils over a range of pH, although alkaline soils seem more conducive to its growth. It is also known from the roots of wheat, oat and barley. In addition, ''M. plumbeus'' is a common fungal contaminant of indoor built environments. This species shares many similarities with '' M. racemosus'', another fungus that belongs to the family Mucoraceae which is known to cause

mucormycosis Mucormycosis, also known as black fungus, is a severe fungal infection that comes under fulminant fungal sinusitis, usually in people who are immunocompromised. It is curable only when diagnosed early. Symptoms depend on where in the body the ...

. ''Mucor plumbeus'' is a common spoilage agent of cheese, apples, apple cider and yogurt.

Morphology and reproduction

''Mucor plumbeus'' produces columella with distinctive, darkly pigmented, finger-like apical projections. Sporangiophores (structures bearing asexual spores) exhibit sympodial and monopodial branching. The appearance of sporangia of ''M. plumbeus'' changes throughout development from hyaline at first becoming dark brown colour at maturity. Sporangiospores are spherical, ranging from 5–7 to 8–10 μm in diameter. Zygospores are also darkly coloured, though much larger than sporangiospores with an average diameter of approximately 85 μm. Zygospores are ornamented with short star-shaped spines (length of 3 μm). The mating system is

heterothallic Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable ...

. Growth on Czapek Yeast Extract Agar (CYA) and Malt Extract Agar (MEA) produces colonies at least 50 mm in diameter, often spreading across the petri dish. The mycelium appear colourless with an overall colour of pale to deep grey from the sporangia. Growth on G25N medium produces colonies 20–35 mm in diameter, which appear white to pale yellow brown. ''Mucor plumbeus'' spores are commonly airborne, which could explain their vast distribution. Chlamydospores have at times been found within sporangiophores.

Physiology

''Mucor plumbeus'' colonies grown in culture were found to develop in the presence of ammonium chloride, L-histidine and urea, suggesting that these compounds are utilised as a nitrogen source. ''Mucor plumbeus'' can also use sucrose, D-mannose, D-sorbitol and citric acid as sources of carbon. Zygospores were found to be unable to grow in culture. ''Mucor plumbeus'' is capable of growing from to . The optimal temperature range for growth and sporulation to occur at was found to be . It does not grow at . Primary growth of ''M. plumbeus'' was found to be greatly suppressed by garlic extract in in-vivo growth studies. Sporulation can be suppressed by rubratoxin B. ''Mucor plumbeus'' can cause self inhibition of its germinating spores with the production of certain factors such as nonanoic acid. In a study conducted to determine the antifungal capabilities of different mixtures of cinnamon and clove oil against various important spoilage microorganisms, ''M. plumbeus'' was discovered to be amongst the most resistant organisms. This study also revealed that

thymol Thymol (also known as 2-isopropyl-5-methylphenol, IPMP), , is a toxic monoterpenoid phenol derivative of ''p''-Cymene, isomeric with carvacrol. It occurs naturally in the oil of thyme, and it is extracted from ''Thymus vulgaris'' (common thy ...

has effective inhibitory action against ''M. plumbeus''. In nature, ''M. plumbeus'' can be found in soils with a wide range in pH - particularly into the alkaline range. The minimum

water activity In food science, water activity (''aw'') of a food is the ratio of its vapor pressure to the vapor pressure of water at the same temperature, both taken at equilibrium. Pure water has a water activity of one. Put another way, ''aw'' is the equi ...

(aw) for growth was reported to be 0.93. The growth of ''M. plumbeus'' varied with different gas concentrations. Growth in N was 80% of that in air. Growth also occurred in an atmosphere of more than 97% CO with trace amounts of O. Growth on cheddar cheese in an atmosphere of: 20% CO and 5% O was 50% of that in air; 20% CO and 1% O was 40% of that in air; 40% CO and 5% O was 50% of that in air; 40% CO and 1% O was 30% of that in air.

Symbiotic interactions

Hyphae of ''Mucor plumbeus'' have been found to be invaded by the hyperparasitic fungi ''Trichoderma viride'' and ''Synchephalis californica''. In addition, ''Mucor plumbeus'' produces a gas that stimulates the growth of ''Phytophthora citrophthora'', a plant pathogen. The presence of ''M. plumbeus'' stimulates the fruiting of ''Pilobolus kleinii'' due to the production of

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

Health implications

As of yet, there have not been any reported cases of mycosis associated with ''M. plumbeus''. However, studies have revealed that the spores of ''M. plumbeus'' have the ability to activate the complement system in humans via the alternative pathway. In addition, studies involving various complement proteins on fungal surfaces suggest that ''M. plumbeus'' spores can activate all pathways of the complement system. ''Mucor plumbeus'' is not known to produce any mycotoxins.

Distribution

''Mucor plumbeus'' is distributed worldwide. Samples of ''M. plumbeus'' have been collected in numerous countries: as far north as

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

; as far east as

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

; as far west as

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

and far south as

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

. It is found in dust, soil and hypersaline water. ''Mucor plumbeus'' tolerates many soil types: including grassland, desert soils and heathland and has been isolated from the roots of

alfalfa Alfalfa () (''Medicago sativa''), also called lucerne, is a perennial plant, perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, ...

oats The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural). Oats appear to have been domesticated as a secondary crop, as their seed ...

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

, '' Holcus mollis'' and other Australian

heathland A heath () is a shrubland habitat found mainly on free-draining infertile, acidic soils and is characterised by open, low-growing woody vegetation. Moorland is generally related to high-ground heaths with—especially in Great Britain—a coole ...

plants. In addition, it has been isolated from bird feathers, hay, decomposing plant debris, dung from different animals, fresh water, wood pulp, beech bark, wood timbers used in a copper mine, seeds of wheat and oat, and

pecan The pecan ( , , ; ''Carya illinoinensis'') is a species of hickory native to the Southern United States and northern Mexico in the region of the Mississippi River. The tree is cultivated for its seed primarily in the U.S. states of Georgia ( ...

s. In the indoor built environment, ''M. plumbeus'' has been isolated from HVAC filters and has been detected in hospital air. In addition, ''M. plumbeus'' has been found to be associated with mould growth on concrete and other floor related materials and house dust. It is also known from foods such as meat, nuts and cereals, and has been isolated in low levels from black rice in Thailand,

soybean The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean. Soy is a staple crop, the world's most grown legume, and an important animal feed. Soy is a key source o ...

s in the Philippines and from

coriander Coriander (), whose leaves are known as cilantro () in the U.S. and parts of Canada, and dhania in parts of South Asia and Africa, is an annual plant, annual herb (''Coriandrum sativum'') in the family Apiaceae. Most people perceive the ...

in Indonesia.

Chemistry

A range of polysaccharides have been found in the extracellular and intracellular compartments of ''M. plumbeus'' including

fucose Fucose is a hexose deoxy sugar with the chemical formula C6H12O5. It is found on ''N''-linked glycans on the mammalian, insect and plant cell surface. Fucose is the fundamental sub-unit of the seaweed polysaccharide fucoidan. The α(1→3) l ...

glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...

galactose Galactose (, ''wikt:galacto-, galacto-'' + ''wikt:-ose#Suffix 2, -ose'', ), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweetness, sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epime ...

and

mannose Mannose is a sugar with the formula , which sometimes is abbreviated Man. It is one of the monomers of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylatio ...

Glucuronic acid Glucuronic acid (GCA, from ) is a uronic acid that was first isolated from urine (hence the name "uronic acid"). It is found in many natural gum, gums such as gum arabic ( 18%), xanthan, and kombucha tea and is important for the metabolism of ...

, a carbohydrate with a similar structure to glucose, is located specifically in the extracellular region of ''M. plumbeus''. The monosaccharide

glucosamine Glucosamine (C6H13NO5) is an amino sugar and a prominent precursor in the biochemical synthesis of glycosylated proteins and lipids. Glucosamine is part of the structure of two polysaccharides, chitosan and chitin. Glucosamine is one of the mo ...

was found only in the intracellular regions of ''M. plumbeus''. ''Mucor plumbeus'' has the ability to detoxify

pentachlorophenol Pentachlorophenol (PCP) is an organochlorine compound used as a pesticide and a disinfectant. First produced in the 1930s, it is marketed under many trade names. It can be found as pure PCP, or as the sodium salt of PCP, the latter of which disso ...

and has been used in the biotransformation of other products. Incubation of ''M. plumbeus'' with the natural product maalioxide produces three metabolites (1,7 and 9 β-hydroxymaalioxide). ''Mucor plumbeus'' activity towards camphorquinone is stereoselective. Extracts of ''Mucor plumbeus'' have shown acetylcholinesterase enzyme inhibition activity. ''Mucor plumbeus'' is able to biocatalyze the hydroxylation of

terpenes Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n ≥ 2. Terpenes are major biosynthetic building blocks. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predomi ...

and

steroids A steroid is an organic compound with four fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter mem ...

by cytochrome p450 enzymes in the presence of O and cofactor

NADPH Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require N ...

. ''Mucor plumbeus'' also transforms sesquiterpene into a series of 12 degradation products of 10,15-epoxidation. As well, squamulosone (aromadendr-1(10)-en-9-one) is biotransformed by ''M. plumbeus'' to yield an array of terpenes.

References

External links

Index Fungorum

USDA ARS Fungal Database
{{Taxonbar, from=Q10589909 Fungi described in 1878 Mucoraceae Fungus species Taxa named by Hermann Friedrich Bonorden