Aspergillus parasiticus

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Aspergillus parasiticus
Aspergillus parasiticus UAMH3108.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Eurotiomycetes
Order: Eurotiales
Family: Aspergillaceae
Genus: Aspergillus
Species:
A. parasiticus
Binomial name
Aspergillus parasiticus
Speare (1912)
Type strain
UAMH 9603
Synonyms
  • Aspergillus flavus subsp. parasiticus(Speare) Kurtzman, M.J. Smiley, Robnett & Wicklow (1986)
  • Petromyces parasiticusPetromyces parasiticus (2009)
  • Aspergillus chungiiY.K. Shih, Lingnan (1936)

Aspergillus parasiticus is a fungus belonging to the genus Aspergillus . [1] This species is an unspecialized saprophytic mold, mostly found outdoors in areas of rich soil with decaying plant material as well as in dry grain storage facilities. [2] Often confused with the closely related species, A. flavus, A. parasiticus has defined morphological and molecular differences. [3] Aspergillus parasiticus is one of three fungi able to produce the mycotoxin, aflatoxin, one of the most carcinogenic naturally occurring substances. [3] Environmental stress can upregulate aflatoxin production by the fungus, which can occur when the fungus is growing on plants that become damaged due to exposure to poor weather conditions, during drought, by insects, or by birds. [2] In humans, exposure to A. parasiticus toxins can cause delayed development in children and produce serious liver diseases and/or hepatic carcinoma in adults. [3] The fungus can also cause the infection known as aspergillosis in humans and other animals. A. parasiticus is of agricultural importance due to its ability to cause disease in corn, peanut, and cottonseed. [2] [4]

Contents

History and taxonomy

Aspergillus parasiticus was first discovered in 1912 by pathopathologist, A.T Speare from dead mealy bugs collected on Hawaiian sugarcane plantations. [4] The species epithet, "parasiticus" is derived from the Latin word meaning "parasite" and was selected due to the ability of the fungus to parasitize other organisms. [5] The fungus was originally classified as a subspecies of A. flavus called Aspergillus flavus subsp. parasiticus (Speare) due to its strong resemblance to A. flavus. Indeed, this fungus is very closely related to A. flavus [3] and is often misidentified as the latter. [3] However, the two species are separable based on morphological features. [3] A. parasiticus also exhibits physiological differences from A. flavus such as the inability to produce cyclopiazonic acid and the production of aflatoxin G. [6]

Growth and morphology

Aspergillus parasiticus UAMH5727b.jpg
Aspergillus parasiticus UAMH5727a.jpg
Conidia (left) and conidiophores (right) of A. parasiticus grown in slide culture for 6 days

The conidia of A. parasiticus have rough, thick walls, are spherical in shape, have short conidiophores (~400 μm) [5] with small vesicles averaging 30 μm in size to which the phialides are directly attached. [3] A. parasiticus is further distinguished by its dark green colony colour. [2] [1] [7] Aspergillus parasiticus colonies are dark green. The average growth temperature for this fungus ranges between 12 and 42 °C with the optimum temperature for growth is at 32 °C and no growth reported at 5 °C. [3] Growth pH ranges from 2.4 to 10.5 with the optimum growth ranging between 3.5–8. [3] For the best growth of the fungus the carbon and nitrogen content in the soil is 1:1 and the pH 5.5. [8] A. parasiticus normally reproduces asexually [2] however, the presence of single mating genes MAT1-1 or MAT1-2 in different strains of the fungus suggests it has a heterothallic mating system and may have a hitherto unrecognized teleomorph. [2] [4] [7] A. parasiticus grows on cereal agar, Czapek agar, malt extract agar, malt salt agar, and potato dextrose agar. The sclerotia and stromata transform from white to pink, dark brown and black. [2] When grown on "Aspergillus flavus and parasiticus" agar (AFPA), colonies show an orange yellow reverse colouration. [3] [9] The conidia are pink when grown on media containing anisaldehyde. [5]

A. parasiticus has been cultivated on both Czapek yeast extract agar (CYA) plates and Malt Extract Agar Oxoid (MEAOX) plates. The growth morphology of the colonies can be seen in the pictures below.

Physiology

A. parasiticus produces aflatoxins B1, B2, G1, and G2, named for the colours emitted under UV light on thin-layer chromatography plates—either blue and green. The numbers refer to the type of compound with 1 being major and 2 being minor. [3] These aflatoxins are carcinogenic mycotoxins which have detrimental effects to humans and livestock. [4] A. parasiticus also has the ability to produce kojic acid, aspergillic acid, nitropropionic acid and aspertoxin [1] as secondary antimicrobial metabolites in response to different environments, all of which can be useful in identification. [10] A. parasiticus also differs in sclerotia quantity number, volume, and shape. [11] This fungus can be reliably identified using molecular methods. [3]

A. parasiticus produces aflatoxins at higher concentrations than A. flavus in temperatures ranging from 12–42 °C (54–108 °F) with pH ranging from 3 to greater than 8. [3] Light exposure, oxidative growth conditions, fungal volatiles and nutrient availability (sugars and zinc) affect the production of these toxins. Greater zinc availability increases aflatoxin output. [12] Environmental stress caused by drought and/or high temperatures during the latter part of the growing season of crops increases the likelihood of fungal growth. [13] The aflatoxins produced by A. parasiticus are hazardous under normal food handling conditions and are especially stable when absorbed by starch or protein on the surfaces of seeds. [5]

Signs and symptoms

Often, food illnesses are not attributed to A. parasiticus because it is mistaken for A. flavus. [3] Serious symptoms of aflatoxin exposure by either ingestion or inhalation of spores, or through direct skin contact, can occur amongst humans and animals. Signs and symptoms of exposure in humans may include delayed development and stunted growth among children, while adults may experience teratogenic effects, [3] lung damage, ulcers, skin irritation, fever, and acute liver disease, which can later lead to liver carcinoma and death. [2]

Control and management

Most countries put low limits on how much aflatoxin is allowed to be in food. [3] This fungus has low resistance to heat, [3] so in order to reduce [aflatoxin] levels and its toxic effects, foods such as peanuts, hazelnuts, walnuts, pistachios, and pecans [3] can be roasted, can be treated with an alkali such as ammonia, or the crops can be given a microbial treatment. [2] The growth of this fungus can be prevented by proper water management and dust reduction. [2] Corn contaminated by A. parasiticus can be pasteurized by exposure to radio frequency (although any mycotoxins produced in situ will remain intact). [14] Exposure of the fungus to phenolic compounds destabilizes the cellular lipoprotein membrane by increasing hydrophobicity, resulting in a lengthened lag phase, reduction of growth rate and diminished aflatoxin production. [15] Similarly, exposure to phytochemicals such as ascorbic acid, gallic acid, caffeine, and quercetin reduces the growth rate of A. parasiticus. [16]

Habitat and ecology

Aspergillus parasiticus can be found outdoors commonly within an agricultural setting of soil on fields and through the improper handling, drying, transportation and storage of grains and fresh produce. [2] [17] This fungus is also commonly found on the stems and roots of peanuts and other plants. [18]

A. parasiticus is a tropical and subtropical species found in the United States, Latin America, South Africa, India and Australia. This species has rarely been reported from Southeast Asia and cool temperate zones. [3]

Fungal spores can be distributed with the wind as well as through moist soil via contact with nuts and kernels, and can survive over the winter months on plant material on the soil. [2]

Related Research Articles

<span class="mw-page-title-main">Aflatoxin</span> Group of poisons produced by moulds

Aflatoxins are various poisonous carcinogens and mutagens that are produced by certain molds, particularly Aspergillus species. The fungi grow in soil, decaying vegetation and various staple foodstuffs and commodities such as hay, sweetcorn, wheat, millet, sorghum, cassava, rice, chili peppers, cottonseed, peanuts, tree nuts, sesame seeds, sunflower seeds, and various spices. In short, the relevant fungi grow on almost any crop or food. When such contaminated food is processed or consumed, the aflatoxins enter the general food supply. They have been found in both pet and human foods, as well as in feedstocks for agricultural animals. Animals fed contaminated food can pass aflatoxin transformation products into eggs, milk products, and meat. For example, contaminated poultry feed is the suspected source of aflatoxin-contaminated chicken meat and eggs in Pakistan.

<i>Aspergillus niger</i> Species of fungus

Aspergillus niger is a mold classified within the Nigri section of the Aspergillus genus. The Aspergillus genus consists of common molds found throughout the environment within soil and water, on vegetation, in fecal matter, on decomposing matter, and suspended in the air. Species within this genus often grow quickly and can sporulate within a few days of germination. A combination of characteristics unique to A. niger makes the microbe invaluable to the production of many acids, proteins and bioactive compounds. Characteristics including extensive metabolic diversity, high production yield, secretion capability, and the ability to conduct post-translational modifications are responsible for A. niger's robust production of secondary metabolites. A. niger's capability to withstand extremely acidic conditions makes it especially important to the industrial production of citric acid.

A mycotoxin is a toxic secondary metabolite produced by fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops.

<i>Aspergillus flavus</i> Species of fungus

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.

<i>Aspergillus</i> Genus of fungi

Aspergillus is a genus consisting of several hundred mould species found in various climates worldwide.

<i>Aspergillus oryzae</i> Filamentous fungus

Aspergillus oryzae, also known as kōji mold, is a filamentous fungus used in East Asia to saccharify rice, sweet potato, and barley in the making of alcoholic beverages such as sake and shōchū, and also to ferment soybeans for making soy sauce and miso. However, in the production of fermented foods of soybeans such as soy sauce and miso, Aspergillus sojae is sometimes used instead of A. oryzae. Incidentally, in China and Korea, the fungi used for fermented foods for a long time in the production of traditional alcoholic beverages were not A. oryzae but fungi belonging to Rhizopus and Mucor. A. oryzae is also used for the production of rice vinegars. Barley kōji (麦麹) or rice kōji (米麹) are made by fermenting the grains with A. oryzae hyphae.

<i>Rhizopus oligosporus</i> Species of fungus

Rhizopus oligosporus is a fungus of the family Mucoraceae and is a widely used starter culture for the production of tempeh at home and industrially. As the mold grows it produces fluffy, white mycelia, binding the beans together to create an edible "cake" of partly catabolized soybeans. The domestication of the microbe is thought to have occurred in Indonesia several centuries ago.

Mycotoxicology is the branch of mycology that focuses on analyzing and studying the toxins produced by fungi, known as mycotoxins. In the food industry it is important to adopt measures that keep mycotoxin levels as low as practicable, especially those that are heat-stable. These chemical compounds are the result of secondary metabolism initiated in response to specific developmental or environmental signals. This includes biological stress from the environment, such as lower nutrients or competition for those available. Under this secondary path the fungus produces a wide array of compounds in order to gain some level of advantage, such as incrementing the efficiency of metabolic processes to gain more energy from less food, or attacking other microorganisms and being able to use their remains as a food source.

<span class="mw-page-title-main">Sterigmatocystin</span> Chemical compound

Sterigmatocystin is a polyketide mycotoxin produced by certain species of Aspergillus. The toxin is naturally found in some cheeses.

<i>Aspergillus terreus</i> Species of fungus

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.

Aflatoxin B<sub>1</sub> Chemical compound

Aflatoxin B1 is an aflatoxin produced by Aspergillus flavus and A. parasiticus. It is a very potent carcinogen with a TD50 3.2 μg/kg/day in rats. This carcinogenic potency varies across species with some, such as rats and monkeys, seemingly much more susceptible than others. Aflatoxin B1 is a common contaminant in a variety of foods including peanuts, cottonseed meal, corn, and other grains; as well as animal feeds. Aflatoxin B1 is considered the most toxic aflatoxin and it is highly implicated in hepatocellular carcinoma (HCC) in humans. In animals, aflatoxin B1 has also been shown to be mutagenic, teratogenic, and to cause immunosuppression. Several sampling and analytical methods including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectrometry, and enzyme-linked immunosorbent assay (ELISA), among others, have been used to test for aflatoxin B1 contamination in foods. According to the Food and Agriculture Organization (FAO), a division of the United Nations, the worldwide maximum tolerated levels of aflatoxin B1 was reported to be in the range of 1–20 μg/kg (or .001 ppm - 1 part-per-billion) in food, and 5–50 μg/kg (.005 ppm) in dietary cattle feed in 2003.

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 penicillioides is a species of fungus in the genus Aspergillus, and is among the most xerophilic fungi.

<i>Aspergillus versicolor</i> Species of fungus

Aspergillus versicolor is a slow-growing 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.

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.

<i>Aspergillus tubingensis</i> Species of fungus

Aspergillus tubingensis is a darkly pigmented species of fungus in the genus Aspergillus section Nigri. It is often confused with Aspergillus niger due to their similar morphology and habitat. A. tubingensis is often involved in food spoilage of fruits and wheat, and industrial fermentation. This species is a rare agent of opportunistic infection.

Aspergillus leporis is an anamorph species of fungus in the genus Aspergillus. It is from the Flavi section. The species was first described in 1979. It has been isolated from the dung of Lepus townsendii. Aspergillus leporis produces leporin A and leporin B. It has also been reported to produce antibiotic Y, kojic acid, and pseurotin.

Aspergillus nomius is a species of fungus in the genus Aspergillus. It is from the Flavi section. The species was first described in 1987. It has been reported to produce aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, aspergillic acid, kojic acid, nominine, paspaline, pseurotin, and tenuazonic acid. A. nomius has been identified as the cause of human infections.

Aspergillus wentii is an asexual, filamentous, endosymbiotic fungus belonging to the mold genus, Aspergillus. It is a common soil fungus with a cosmopolitan distribution, although it is primarily found in subtropical regions. Found on a variety of organic materials, A. wentii is known to colonize corn, cereals, moist grains, peanuts and other ground nut crops. It is also used in the manufacture of biodiesel from lipids and is known for its ability to produce enzymes used in the food industry.

John Ingram Pitt was an Australian mycologist, known as a leading expert on the role of fungi in food spoilage. He gained an international reputation as a pioneering researcher on the ecology of spoilage moulds in extreme environments and of dried fruits and other dried foodstuffs.

References

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  2. 1 2 3 4 5 6 7 8 9 10 11 12 Sobel, Lanette. "Aspergillus parasiticus". Bugwood Wiki. Retrieved 21 November 2017.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Pitt, J.I.; Hocking, A.D. (1999). Fungi and food spoilage (2nd ed.). Gaithersburg, Md.: Aspen Publications. ISBN   978-0834213067.
  4. 1 2 3 4 Horn, Bruce W.; Ramirez-Prado, Jorge H.; Carbone, Ignazio (20 January 2017). "The sexual state of". Mycologia. 101 (2): 275–280. doi:10.3852/08-205. JSTOR   20619175. PMID   19397202. S2CID   28375699.
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  6. ↑ Rodrigues, P.; Santos, C.; Venâncio, A.; Lima, N. (October 2011). "Species identification of Aspergillus section Flavi isolates from Portuguese almonds using phenotypic, including MALDI-TOF ICMS, and molecular approaches". Journal of Applied Microbiology. 111 (4): 877–892. doi: 10.1111/j.1365-2672.2011.05116.x . PMID   21790915.
  7. 1 2 Ramirez-Prado, Jorge H.; Moore, Geromy G.; Horn, Bruce W.; Carbone, Ignazio (September 2008). "Characterization and population analysis of the mating-type genes in Aspergillus flavus and Aspergillus parasiticus". Fungal Genetics and Biology. 45 (9): 1292–1299. doi:10.1016/j.fgb.2008.06.007. PMID   18652906.
  8. ↑ Al-Gabr, H; Ye, C; Zhang, Y; Khan, S; Lin, H; Zheng, T (April 2013). "Effects of carbon, nitrogen and pH on the growth of aspergillum parasiticus and aflatoxins production in water". Journal of Environmental Biology. 34 (2): 353–358. ProQuest   1355249650.
  9. ↑ Corey, JEL; Curtis, GDW; Baird, RM (2003). Aspergillus flavus and parasiticus agar (AFPA). Progress in Industrial Microbiology. Vol. 37. pp. 397–399. doi:10.1016/S0079-6352(03)80029-2. ISBN   9780444510846.
  10. ↑ Bracarense, Adriana A.P.; Takahashi, Jacqueline A. (2014). "Modulation of antimicrobial metabolites production by the fungus Aspergillus parasiticus". Brazilian Journal of Microbiology. 45 (1): 313–321. doi:10.1590/S1517-83822014000100045. PMC   4059316 . PMID   24948950.
  11. ↑ Horn, B. W.; Greene, R. L.; Sobolev, V. S.; Dorner, J. W.; Powell, J. H.; Layton, R. C. (1996). "Association of Morphology and Mycotoxin Production with Vegetative Compatibility Groups in Aspergillus flavus, A. parasiticus, and A. tamarii". Mycologia. 88 (4): 574–587. doi:10.2307/3761151. JSTOR   3761151.
  12. ↑ Wee, Josephine; Day, Devin; Linz, John (2 June 2016). "Effects of Zinc Chelators on Aflatoxin Production in Aspergillus parasiticus". Toxins. 8 (6): 171. doi: 10.3390/toxins8060171 . PMC   4926138 . PMID   27271668.
  13. ↑ Guo, Baozhu; Chen, Xiaoping; Dang, Phat; Scully, Brian T; Liang, Xuanqiang; Holbrook, C Corley; Yu, Jiujiang; Culbreath, Albert K (2008). "Peanut gene expression profiling in developing seeds at different reproduction stages during Aspergillus parasiticus infection". BMC Developmental Biology. 8 (1): 12. doi: 10.1186/1471-213X-8-12 . PMC   2257936 . PMID   18248674.
  14. ↑ Zheng, Ajuan; Zhang, Lihui; Wang, Shaojin (May 2017). "Verification of radio frequency pasteurization treatment for controlling Aspergillus parasiticus on corn grains". International Journal of Food Microbiology. 249: 27–34. doi:10.1016/j.ijfoodmicro.2017.02.017. PMID   28271854.
  15. ↑ Pizzolitto, Romina P.; Barberis, Carla L.; Dambolena, José S.; Herrera, Jimena M.; Zunino, María P.; Magnoli, Carina E.; Rubinstein, Héctor R.; Zygadlo, Julio A.; Dalcero, Ana M. (2015). "Inhibitory Effect of Natural Phenolic Compounds on Growth". Journal of Chemistry. 2015: 1–7. doi: 10.1155/2015/547925 . hdl: 11336/15759 .
  16. ↑ Tiwari, Shraddha; Gupta, Nupur; Malairaman, Udayabanu; Shankar, Jata (9 September 2017). "Anti-aspergillus Properties of Phytochemicals Against Aflatoxin Producing Aspergillus flavus and Aspergillus parasiticus". National Academy Science Letters. 40 (4): 267–271. doi:10.1007/s40009-017-0569-y. S2CID   256341844.
  17. ↑ Jantapan, K; Poapolathep, A; Imsilp, K; Poapolathep, S; Tanhan, P; Kumagai, S; Jermnak, U (9 June 2016). "Inhibitory Effects of Thai Essential Oils on Potentially Aflatoxigenic Aspergillus parasiticus and Aspergillus flavus". Biocontrol Science. 22 (1): 31–40. doi: 10.4265/bio.22.31 . PMID   28367868.
  18. ↑ KLICH, MAREN A. (November 2007). "Aspergillus flavus: the major producer of aflatoxin". Molecular Plant Pathology. 8 (6): 713–722. doi: 10.1111/j.1364-3703.2007.00436.x . PMID   20507532.
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