Aspergillus giganteus | |
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Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Eurotiomycetes |
Order: | Eurotiales |
Family: | Aspergillaceae |
Genus: | Aspergillus |
Species: | A. giganteus |
Binomial name | |
Aspergillus giganteus Wehmer (1901) [1] | |
Aspergillus giganteus is a species of fungus in the genus Aspergillus (from Latin "aspergillum," meaning "holy water sprinkler") that grows as a mold. [2] It was first described in 1901 by Wehmer, [1] and is one of six Aspergillus species from the Clavati section of the subgenus Fumigati. [3] Its closest taxonomic relatives are Aspergillus rhizopodus (Rai et al., 1975) [4] [3] and Aspergillus longivescia (Huang and Raper, 1971). [5] [3]
Like the majority of Aspergillus species, [6] A. giganteus reproduces asexually, and has not been observed in a sexual state. [3] Similar to other species in Clavati, A. giganteus produces numerous conidiophores that are characterized by glassy and translucent stem-like structures called stipes and club-shaped aspergilla that taper towards the tips. [3] Blue-green colored asexual spores called conidia form on these tips. [3]
On a macroscopic level, A. giganteus colonies are characterized by their velvety texture. [3] Colonies are often white at first, turning a pale blue-green color when exposed to light. [3]
On a microscopic level, A. giganteus produces two types of conidiophores that have distinct stipes and vesicles. The first of these conidiophores are typically 2-3 mm tall, including stipe length. [3] These shorter conidiophores produces clavate vesicles that are 100-250 μm long and 30-50 μm wide. [3] The second type of conidiophores are much larger, approximately 1-5 cm long. [3] Most of this length is due to elongated stipes. [3] These more elongated conidiophores are phototropic, meaning that they are only able to develop and grow in the presence of light. [3] The vesicles produced by the long conidiophores are 400-600 μm long and 120-180 μm wide, more than double the size of the vesicles produced by their shorter counterparts. [3]
Together the vesicle and phialides form the conidial head. In A. giganteus, these heads are blue-green in color, and split into two or more columns as the mold matures. [3] Conidia form from these conidial heads. The conidia of A. giganteus are relatively thick-walled, and are distinguishable by their smooth, elliptical appearance as well as their size (3.5-4.5 x 2.4-3.0 μm). These traits are characteristic of both types of conidiophore. [3] A. giganteus can be distinguished form other Aspergillus species placed within the Clavati section by its microscopic morphology and by its unique combination of extrolites, which are compounds synthesized by and then excreted by cells in defense against bacteria and other fungi. [3] [8] Morphologically, A. giganteus lacks the rhizoidal foot cells present in A. rhizopodus, and has clavate vesicles that stand in contrast to the elongated vesicles of A. longivesica. [3] In terms of extrolite synthesis, although A. giganteus produces mycotoxins and antibiotics that are characteristic of all Clavati section species (such as patulin, [8] tryptoquivalines and tryptoquivalones, [3] and alpha-sarcins), [9] it also produces extrolites not synthesized by its closest relatives. These include several different carotinoids [10] and penicillin-like clavinformin. [11]
A. giganteus is found worldwide, and has been officially documented in Nigeria, the United States, Egypt, Mexico, Panama, Germany, Suriname, the Netherlands, and Poland. [3] It is most often dung-borne, but will grow in alkaline soil and wood substrates. [3] As a saprotrophic mold, [2] A. giganteus gets its energy by absorbing nutrients from the substrates it grows in. Although many other Aspergillus and Clavati section species are known pathogens of humans, A. giganteus does not have any reported pathogenic effects. [3]
In the lab, A. giganteus has been cultivated on both Czapek yeast extract agar (CYA) plates and Malt Extract Agar Oxoid® (MEAOX) plates, [3] as shown below.
A. giganteus produces an antifungal protein (AFP) that has potential applications for preventing fungal infection in both pharmaceutical and agricultural settings. AFP has been shown to restrict the growth of numerous economically-important filamentous fungi. [12] These include Aspergillus fumigatus , the main cause of aspergillosis in humans, [12] and other Aspergillus species; [13] Fusarium oxysporum and related Fusarium species, [12] common pathogens of tomato, bean, banana, melon, cotton, and chickpea plants; [14] Magnaporthe grisea , a pathogen of rice and cereal crops; [2] and Botrytis cineara, pathogenic to geranium and other economically important ornamental plants. [15] Additionally, AFP may restrict the growth of the oomycete Phytopthera infestans , [2] the pathogen infamous for causing late blight in potatoes (the main cause of the Great Famine of Ireland) and tomatoes. [16]
In additional to having high potential for success in combatting the infections listed above, AFP does not inhibit the viability of yeast, bacteria, mammalian, [17] or plant cells. [18] Because there are many filamentous fungal species that do not respond to AFP, it is likely that the protein's detrimental effects are species-specific. [13] [19] As such, AFP could be used to treat and prevent infection by very specific pathogens without harm to patients or host plants. Furthermore, the protein can be easily synthesized through fermentation of A. giganteus and is resistant to hear. In comparison to other antifungal treatments, small amounts of the protein are needed to prevent the growth of harmful pathogens. [20] In combination with the fact that AFP almost completely blocks growth of sensitive, pathogenic fungi (unlike the ozone, hydrogen peroxide, and chlorine dioxide antifungal treatments currently used in agricultural systems,) [18] these factors highlight AFP's potential as a cheap, mass-producible, and extremely effective solution to pathogen infection.
The cysteine-rich, [20] amphipathic [13] protein inhibits the growth of AFP-senstivie pathogens through multiple pathways. First, AFP may inhibit cell growth by inhibiting chitin synthesis. [12] In sensitive fungi, AFP activates the cell wall integrity pathway, thereby enhancing the expression of the α-1,3-glucan synthase A gene responsible for remodeling cell walls and inhibiting the formation of chitin. [21] AFP may also alter the cell membrane permeability of sensitive fungi, [19] particularly of Aspergillus niger, [13] or cause an immediate, sustained increase in calcium cation cell resting potential that often results in programmed cell death. [21] Each of these pathways ultimately results in the death of the AFP-sensitive pathogen. Although more research is needed to identify how these pathways work in consort, the wide variety of AFP modes of action highlights that the protein may interact with sensitive pathogens in different ways, that these pathogens vary in their susceptibility to AFP. [13]
In preliminary studies on the pharmaceutical and agricultural applications of AFP, researchers used AFP to halt the growth of Phytopthera infestans [2] and Aspergillus species [12] [13] [19] in culture. In applying AFP solutions to plant leaves and roots, infections by Botrytis cineara in geranium plants [15] and Magnaporthe grisea in rice plants were eliminated. [2] In each of these cases, AFP caused deformations in the hyphae of the sensitive fungi, resulting in reduced hyphal elongation and inability of the pathogen to grow. [2] [15] In addition to direct application to plant structures, the AFP-encoding gene can be edited into the genomes of the plants affected by the AFP-sensitive fungi such that the plants are able to synthesize the protein on their own. [22] [23] [24] This technique has been successfully used to decrease infection by Puccinia substriata, the main cause of rust disease, and Sclerospora graminicola, a causal agent of downy mildew, in pearl millet plants, [22] as well as infection by Magnaporthe grisea in rice plants. [23] [24] Although genetic enhancement halted infection in laboratory and greenhouse settings, researchers continue to debate about the scalability of plant genome editing and the ability of plants themselves to synthesize enough AFP to fight off pathogen infection in the field. [23] [24]
Aspergillus flavus is a saprotrophic and pathogenic fungus with a cosmopolitan distribution. It is best known for its colonization of cereal grains, legumes, and tree nuts. Postharvest rot typically develops during harvest, storage, and/or transit. Its specific name flavus derives from the Latin meaning yellow, a reference to the frequently observed colour of the spores. A. flavus infections can occur while hosts are still in the field (preharvest), but often show no symptoms (dormancy) until postharvest storage or transport. In addition to causing preharvest and postharvest infections, many strains produce significant quantities of toxic compounds known as mycotoxins, which, when consumed, are toxic to mammals. A. flavus is also an opportunistic human and animal pathogen, causing aspergillosis in immunocompromised individuals.
Magnaporthe grisea, also known as rice blast fungus, rice rotten neck, rice seedling blight, blast of rice, oval leaf spot of graminea, pitting disease, ryegrass blast, Johnson spot, neck blast, wheat blast and Imochi (稲熱), is a plant-pathogenic fungus and model organism that causes a serious disease affecting rice. It is now known that M. grisea consists of a cryptic species complex containing at least two biological species that have clear genetic differences and do not interbreed. Complex members isolated from Digitaria have been more narrowly defined as M. grisea. The remaining members of the complex isolated from rice and a variety of other hosts have been renamed Magnaporthe oryzae, within the same M. grisea complex. Confusion on which of these two names to use for the rice blast pathogen remains, as both are now used by different authors.
An appressorium is a specialized cell typical of many fungal plant pathogens that is used to infect host plants. It is a flattened, hyphal "pressing" organ, from which a minute infection peg grows and enters the host, using turgor pressure capable of punching through even Mylar.
Echinocandins are a class of antifungal drugs that inhibit the synthesis of β-glucan in the fungal cell wall via noncompetitive inhibition of the enzyme 1,3-β glucan synthase. The class has been termed the "penicillin of antifungals," along with the related papulacandins, as their mechanism of action resembles that of penicillin in bacteria. β-glucans are carbohydrate polymers that are cross-linked with other fungal cell wall components, the fungal equivalent to bacterial peptidoglycan. Caspofungin, micafungin, and anidulafungin are semisynthetic echinocandin derivatives with limited clinical use due to their solubility, antifungal spectrum, and pharmacokinetic properties.
Aspergillus terreus, also known as Aspergillus terrestris, is a fungus (mold) found worldwide in soil. Although thought to be strictly asexual until recently, A. terreus is now known to be capable of sexual reproduction. This saprotrophic fungus is prevalent in warmer climates such as tropical and subtropical regions. Aside from being located in soil, A. terreus has also been found in habitats such as decomposing vegetation and dust. A. terreus is commonly used in industry to produce important organic acids, such as itaconic acid and cis-aconitic acid, as well as enzymes, like xylanase. It was also the initial source for the drug mevinolin (lovastatin), a drug for lowering serum cholesterol.
Fusarium solani is a species complex of at least 26 closely related filamentous fungi in the division Ascomycota, family Nectriaceae. It is the anamorph of Nectria haematococca. It is a common soil fungus and colonist of plant materials. Fusarium solani is implicated in plant disease as well as human disease notably infection of the cornea of the eye.
Pathogenic fungi are fungi that cause disease in humans or other organisms. Although fungi are eukaryotic, many pathogenic fungi are microorganisms. Approximately 300 fungi are known to be pathogenic to humans; their study is called "medical mycology". Fungal infections kill more people than either tuberculosis or malaria—about 2 million people per year.
Chaetomium cupreum is a fungus in the family Chaetomiaceae. It is able to decay in manufactured cellulosic materials, and is known to antagonize a wide range of soil microorganisms. This species is component of the biocontrol agent, Ketomium, a commercial biofungicide. It has also been investigated for use in the production of natural dyes. Chaetomium cupreum is mesophilic and known to occur in harsh environments and can rapidly colonize organic substrates in soil. Laboratory cultures of C. cupreum can be propagated on a range of common growth media including potato dextrose at ambient or higher than ambient temperature producing cottony white colonies with a reddish reverse.
The antifungal proteinfamily is a protein family, with members sharing a structure consisting of five antiparallel beta strands which are highly twisted creating a beta barrel stabilised by four internal disulphide bridges. A cationic site adjacent to a hydrophobic stretch on the protein surface may constitute a phospholipid binding site.
Aspergillus ochraceus is a mold species in the genus Aspergillus known to produce the toxin ochratoxin A, one of the most abundant food-contaminating mycotoxins, and citrinin. It also produces the dihydroisocoumarin mellein. It is a filamentous fungus in nature and has characteristic biseriate conidiophores. Traditionally a soil fungus, has now began to adapt to varied ecological niches, like agricultural commodities, farmed animal and marine species. In humans and animals the consumption of this fungus produces chronic neurotoxic, immunosuppressive, genotoxic, carcinogenic and teratogenic effects. Its airborne spores are one of the potential causes of asthma in children and lung diseases in humans. The pig and chicken populations in the farms are the most affected by this fungus and its mycotoxins. Certain fungicides like mancozeb, copper oxychloride, and sulfur have inhibitory effects on the growth of this fungus and its mycotoxin producing capacities.
Aspergillus versicolor is a slow-growing species of filamentous fungus commonly found in damp indoor environments and on food products. It has a characteristic musty odor associated with moldy homes and is a major producer of the hepatotoxic and carcinogenic mycotoxin sterigmatocystin. Like other Aspergillus species, A. versicolor is an eye, nose, and throat irritant.
Nicholas José Talbot FRS FRSB is Group Leader and Executive Director at The Sainsbury Laboratory in Norwich.
Penicillium digitatum is a mesophilic fungus found in the soil of citrus-producing areas. It is a major source of post-harvest decay in fruits and is responsible for the widespread post-harvest disease in Citrus fruit known as green rot or green mould. In nature, this necrotrophic wound pathogen grows in filaments and reproduces asexually through the production of conidiophores and conidia. However, P. digitatum can also be cultivated in the laboratory setting. Alongside its pathogenic life cycle, P. digitatum is also involved in other human, animal and plant interactions and is currently being used in the production of immunologically based mycological detection assays for the food industry.
Aspergillus unguis is a species of fungus in the genus Aspergillus, and the asexual state (anamorph) of Emericella unguis. Aspergillus unguis is a filamentous soil-borne fungus found on decomposing plant matter and other moist substrates including with building materials and household dust. Aspergillus unguis occurs mainly in tropical and subtropical soils but has also been isolated from various marine and aquatic habitats. The species was first isolated in 1935 by Weill and L. Gaudin. Historically, A. unguis was assigned to the A. nidulans group, a common group of soil-borne fungi due to the resemblance of its ascospores and cleistothecia to those of Emericella nidulans. Aspergillus unguis is distinctive, however, in possessing spicular hyphae. A number of synonyms have been collapsed into this species, including Sterigmatocystis unguis, Aspergillus laokiashanensis and Aspergillus mellinus.
Cladosporium cladosporioides is a darkly pigmented mold that occurs world-wide on a wide range of materials both outdoors and indoors. It is one of the most common fungi in outdoor air where its spores are important in seasonal allergic disease. While this species rarely causes invasive disease in animals, it is an important agent of plant disease, attacking both the leaves and fruits of many plants. This species produces asexual spores in delicate, branched chains that break apart readily and drift in the air. It is able to grow under low water conditions and at very low temperatures.
Madurella mycetomatis is a fungus primarily reported in Central Africa as a cause of mycetoma in humans. It has been misclassified for many years, but with improvement of molecular techniques, its phylogenetic classification has been established. Many methods exist to identify M. mycetomatis, both in lesions and in culture. Histological examination is especially useful, as it has many unique morphological features. Strain-level differences in response to antifungal agents is informative for treatment and laboratory isolation of cultures.
Aspergillus clavatus is a species of fungus in the genus Aspergillus with conidia dimensions 3–4.5 x 2.5–4.5 μm. It is found in soil and animal manure. The fungus was first described scientifically in 1834 by the French mycologist John Baptiste Henri Joseph Desmazières.
Aspergillus alabamensis is a soil fungus in the division Ascomycota first described in 2009 as a segregated taxon of A. terreus. Originally thought to be a variant of A. terreus, A. alabamensis is situated in a distinctive clade identified by genetic analysis. While A. alabamensis has been found to be morphologically similar to Aspergillus terreus by morphological studies, the two differ significantly in active metabolic pathways, with A. alabamensis producing the mycotoxins citrinin and citreoviridin but lacking mevinolin.
Chaetomium elatum is a very common and widely distributed saprotrophic fungus of the Chaetomiaceae family of molds which has been found to grow on many different substances all over the world. It was first established by Gustav Kunze after he observed it growing on dead leaves. Its defining features that distinguish it from other Chaetomium species are its extremely coarse terminal hairs and the lemon-shaped morphology of its ascospores. It produces many metabolites with potential biotechnology uses including one with promise against the rice blast disease fungus, Magnaporthe grisea. It shows very little pathogenic ability causing confirmed disease in only a few plant species.
Microascus manginii is a filamentous fungal species in the genus Microascus. It produces both sexual (teleomorph) and asexual (anamorph) reproductive stages known as M. manginii and Scopulariopsis candida, respectively. Several synonyms appear in the literature because of taxonomic revisions and re-isolation of the species by different researchers. M. manginii is saprotrophic and commonly inhabits soil, indoor environments and decaying plant material. It is distinguishable from closely related species by its light colored and heart-shaped ascospores used for sexual reproduction. Scopulariopsis candida has been identified as the cause of some invasive infections, often in immunocompromised hosts, but is not considered a common human pathogen. There is concern about amphotericin B resistance in S. candida.