Geotrichum candidum

Geotrichum candidum
Scientific classification
Kingdom: Fungi
Phylum: Ascomycota
Class: Saccharomycetes
Subclass: Saccharomycetidae
Order: Saccharomycetales
Family: Endomycetaceae
Genus: Geotrichum
Species: G. candidum
Binomial name
Geotrichum candidum
Link (1809)

Geotrichum candidum is a plant pathogenic fungus that causes sour rot of citrus fruits, tomatoes, carrot and some vegetables.[1]

The fungus can also cause a disease of the lung or other organs in humans known as geotrichosis.

This species also used widely in the production of certain dairy products including rind cheeses such as Camembert, Saint-Nectaire, Reblochon and others. The fungus can also be also found in a Nordic yogurt-like product known as viili where it is responsible for the product's velvety texture.[2]

History

Taxonomy

The genus Geotrichum was described by Johann Heinrich Friedrich Link in 1809 to accommodate the species G. candidum found on decaying leaves. Since then, over 130 taxa have been described in the genus, and hundreds of synonyms have been generated.[3] For example, G. candidum was misclassified as the Oidium lactis in much early literature.[4] Species of Geotrichum resemble the genera Trichosporon and Protendomycopsis; however, Geotrichum is of ascomycetous affiliation whereas the latter are members of the Basidiomycota. Species of Geotrichum are occasionally mistaken for fast growing members of the genus Dipodascus, which are characterized by irregularly branched, 10-14 μm wide hyphae and the production of single-spored asci. However, unlike Geotrichum, members of the genus Dipodascus lack dichotomous branching of the peripheral hyphae and their growth rates are generally less than 3 mm per day.[5]

Phylogeny

Galactomyces candidus, formerly thought to be a distinct taxon, was found to be the sexual state of G. candidum using sequence-based methods[6][7] Geotrichum candidum in the broad sense comprises 3 clades, corresponding to the species G. candidum, G. clavatum and G. fici, all of which are thought to have pathogenic potential.[2][8][9] Species of Geotrichum can be differentiated by sequence analysis of the nuclear ribosomal large subunit (18S ribosomal RNA) or the internal transcribed spacer region of the nuclear ribosomal RNA gene.[6]

Morphology

Anamorph

Geotrichum candidum colonies are thin, spreading, soft, creamy and white in the anamorph state.[10] The fungus G. candidum is characterized by hyphae that appear creeping, mostly submerged and septate.[5][11] The hyphae colour appears to be hyaline or lightly pigmented.[12] When the hyphae becomes airborne it changes shape from arthrocondia to cylindrical or barrel-shaped or ellipsoidal.[5] Chlamydospores are subglobose, solitary, borne on undifferentiated hyphae.[5][11] Blastoconidia sometimes develop on hyphae laterally.[5] Conidia appear arthrosporous, terminal or intercalary, aerial on an agar surface. The conidia size ranges from 4.8–12.5 μm x 2.4–2.5 μm.

Teleomorph

Geotrichum candidum is thought to be homothallic but most isolates are self-sterile.[5] Sexual reproduction was first observed in strains isolated from soils in Puerto Rico.[13] The fungus produces globose asci that contain a single, thick walled, uninucleated, globose to oval ascospore measuring 6–7 μm by 7–10 μm.[5] The ascospores have a smooth inner wall and a furrowed outer wall.[13] The septa are perforated by microspores, arranged in a ring structure. The colonies appear to be growing faster in the sexual stage than the asexual stage. Colonies grow at a rate of 5–7 mm daily at 24 °C (75 °F).[5]

Growth

Geotrichum candidum is fast growing colony that can grow 5–6 cm diameter at 5 days on Sabouraud-glucose agar, wort agar and synthetic media. Microscopically, the growth is characterized by the production of dichotomously branched hyphae that resemble tuning forks along the colony margin. The condia chains become aerial, erect or decumbent and measures 6–12(–20) x 3–6(–9) μm. The fungus can grow on a variety of citrus fruits and cause rotting. It tends to cause rotting in fruits that are stored at 0–5 °C (32–41 °F). The conidia are colourless and have a slimy texture.[14] Geotrichum candidum is also found occasionally in the human gut, feces, sputum and on skin. The fungus grows in soil, water, sewage, various plant substrates, baker’s dough, husks of fermentation, bread, milk and milk products[5] The optimal temperature for growth is 25 °C (77 °F) with a pH range of 5.0–5.5.[4] The temperature range changes depending on the surface that the fungus grows on. For example, in plants the optimum temperature ranges from 25–27 °C (77–81 °F). In animals the optimum temperature ranges from 30–31 °C (86–88 °F).[15] The maximum temperature for growth is 35–38 °C (95–100 °F).[5][10] Fungal growth can be supported by D-glucose, D-mannose, D-xylose, L-sorbose, D-fructose, D-galactose, sucrose, D-mannitol, D-sorbital, ethanol and glycerol. Sporulation often requires balance of carbon and nitrogen.[5]

Distribution

Geotrichum candidum is extremely common in soil and has been isolated from substrates in Canada, United States, Britain, Germany, Austria, India, South Africa, Japan, Brazil and Peru.[5] It is also found as a causal agent in sour rot in citrus fruits— a soft rot associated with the emission of a fruity odour.[16] The fungus is also known as a post-harvest spoilage agent of muskmelon, squash and cucumber. It plays a role in tomato fruit rot when it is stored at 0–5 °C (32–41 °F).[5] It is a naturally occurring colonist of certain dairy products particularly cheeses and is sometime used to inoculate wash-rind and bloomy rind cheeses.[4][6][17]

Human colonization and disease

Geotrichum candidum is also a frequent member of the human microbiome, notably associated with skin, sputum and feces where it occurs in 25-30% of specimens.[5][8] The fungus can cause an infection known as geotrichosis, affecting the oral, bronchial, skin and bronchopulmonary epithelia.[5] The inoculum may arise from endogenous or exogenous sources.

In 1847 Bennett described Geotrichum candidum causing a superinfection in the tuberculous cavity.[18][19] Bennett was able to differentiate infection by Geotrichum candidum from candidiasis, and diagnose the first case of geotrichosis. Other early medical case reports in 1916 and 1928 also described lung infections.[18] Most cases affect the bronchopulmonary tree, although other sites can be involved, such as oral mucosa and vagina.[18] Skin and gut infections are also known.[18] Reported cases of geotrichosis have been characterized with symptoms of chronic or acute bronchitis. Exogenous geotrichosis may arise from contact with contaminated soil, fruits or dairy products.[4]

Diagnosis

Laboratory culture

The diagnoses of geotrichosis cannot be determined without using culture or microscopic measurements.[19] The laboratory diagnosis of geotrichosis involves collected fungi samples areas of infections without contamination.[4] Scraping of the mouth lesions and the ulcers can provide a sample of G. candidum. Samples can also be collected from pus and mucus can be obtained from the feces.[19] Sputum can be searched for the mucoid-like white flakes for further examination.[4][19] Culturing the cylindrical barrel-shaped or elliptical fungi in considerable numbers in oral lesions is an indicator that a patient may have geotrichosis.[4] Under the microscope the fungi appears yeast-like and septate branching hyphae that can be broken down into chains or individual arthrospores. Arthrospores appear rectangular with flat or rounded ends.[8][19] Under the microscope the arthroconidia size range from 6-12μm x 3-6μm. Arthroconidia and coarse true hyphae can be observed can be observed under the microscope.[8] Another identification method for G. candidum is selective isolation method. A selection isolation method based on the fungi tolerance to novobiocin and carbon dioxide can determine if G. candidum is the cause of illness.[5]

Diagnostic imaging

X-rays can be used to examine the lung tissue, however it can not be used to positively diagnose geotrichosis. X-rays may show cavitation that is located the walls of the lungs tissues. The lung tissue resemble the early signs of tuberculosis.[19] The results of an x-ray examination of pulmonary geotrichosis presents smooth, dense patchy infiltrations and some cavities. Bronchial geotrichosis shows peribronchial thickening with fine mottling may be present on middle or basilar pulmonary fields.[18] Bronchial geotrichosis usually present itself as non-specific diffuse peribronchical infiltration.[20]

Treatment

Geotrichosis generally has a good prognosis and patients generally have successful recovery.[13] However, there is not a standard treatment for geotrichosis.[8] There are several types of antimicrobial or antifungal compounds that can be used for geotrichosis treatment.[23] One type of treatment of geotrichosis can involve miconazole and ketoconazole, which has shown to improve cutaneous, branchopulmonary, intestinal and joint conditions.[24] Another method of treatment involves symptomatic care, bed rest, iodine therapy,[19] aerosol nystatin and amphotericin B.[18] Azole drugs including isoconazole and clotrimazole are used for geotrichosis treatment.[23] Associated treatment for pulmonary geotrichosis includes the use of potassium iodide, sulfonamides or colistin.[13] The associated asthma can be treated with desensitization and prednisolone.[13][18] Amphotericin B, clotrimazole and S-fluorocytosine have become more susceptible to G. candidum. Antimycotic resistance can appear due to repeated treatment.[23]

Commercial uses

Geotrichum candidum can be used commercially to inoculate wash-rinds and bloomy rind cheeses.[4][6][17] Cultures can be added to milk, brine or sprayed onto cheese surface. The optimum pH range for growth on cheese ranges from 4.4 to 6.7. The fungus colonizes nearly the entire surface of the cheese during the early stages of ripening. It is found on soft cheeses like Camembert cheese and semi-hard cheese Saint-Nectaire and Reblochon.[4] For the Camembert cheese the fungi grows on the outside of the cheese forming a rind.[17] The fungus is responsible for the uniform, white, velvety coat on Saint-Marcellin cheese.[4] Lipases and proteases from G. candidum release fatty acids and peptides that provide the cheese with distinctive flavors. Geotrichum candidum reduces the bitterness in Camembert cheese through the activity of the aminopeptidases that hydrolyze low molecular weight hydrophobic peptides. Aminopeptidases also contributes an aroma in traditional Norman Camembert. The fungus also neutralize the curd by catabolizing lactic acid produced by bacteria. Geotrichum candidum prepares the cheese for colonization of other acid sensitive bacteria such as Brevibacterium. The fungus inhibits growth of the bacteria Listeria monocytogenes.[25] Commercial strains of G. candidum are available for cheese ripening.[4]

External links

Further reading

References

  1. ↑ Thornton, C.R.; Slaughter, C.D.; Davis, R.M. (2010). "Detection of the Sour-Rot Pathogen Geotrichum candidum in Tomatoes Fruit and Juice by Using a Highly Specific Monoclonal Antibody-Based ELISA". International Journal of Food Microbiology. 143: 166–172. doi:10.1016/j.ijfoodmicro.2010.08.012.
  2. 1 2 Etienne A, Datry A, Gaspar N, et al. (May 2008). "Successful Treatment of Disseminated Geotrichum capitatum Infection with a Combination of Caspofungin and Voriconazole in an Immunocompromised Patient". Mycoses. 51 (3): 270–2. doi:10.1111/j.1439-0507.2007.01484.x. PMID 18399909.
  3. ↑ Anonymous. "Geotrichum". MycoBank.
  4. 1 2 3 4 5 6 7 8 9 10 11 Boutrou, R; Gueguen, M (2005). "Interests in Geotrichum candidum for Cheese Technology". International Journal of Food Microbiology. 102: 1–20. doi:10.1016/j.ijfoodmicro.2004.12.028.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Domsch, K.H.; W. Gams, W.; Andersen, T.H. (1980). Compendium of soil fungi (2nd ed.). London, UK: Academic Press. ISBN 9780122204029.
  6. 1 2 3 4 Alper, I; Michel, F; Labrie, S (2011). "Ribosomal DNA Polymorphisms in the Yeast Geotrichum candidum". Fungal Biology. 115: 1259–1269. doi:10.1016/j.funbio.2011.09.002.
  7. ↑ Sybren de Hoog, G; Smith, M. T (2004). "Ribosomal Phylogeny and Species Delimitation in Geotrichum and its Teleomorphs". Studies in Mycology. 50: 489–515.
  8. 1 2 3 4 5 "Geotrichum spp.". Doctor Fungus. Retrieved 27 October 2014.
  9. ↑ Mycology Online, The University of Adelaide, South Australia
  10. 1 2 Onions, A.H.S.; Allsopp, D.; Eggins, H.O.W. (1981). Smith's Introduction to Industrial Mycology (7th ed.). London, UK: Arnold. ISBN 0-7131-2811-9.
  11. 1 2 Watanabe, Tsuneo. (2010). Pictorial Atlas of Soil and seed Fungi (3rd ed.). Baca Raton, FL: CRC Press. ISBN 9781439804193.
  12. ↑ Barron, G.L. (1968). The Genera of Hyphomycetes from Soil. Baltimore, MD: Williams & Wilkins. ISBN 9780882750040.
  13. 1 2 3 4 5 Kwon-Chung, K.J.; Bennett, J.E.; Bennett, John E. (1992). Medical mycology. Philadelphia: Lea & Febiger. ISBN 0812114639.
  14. ↑ Malloch, David (1981). Moulds: Their Isolation, Cultivation and Identification. Toronto, ON: University of Toronto Press. ISBN 978-0802024183.
  15. ↑ Samson, R.A.; Hoekstra, E.S.; Oorschot, C.A.N (1984). Introduction to Food-borne Fungi (2nd ed.). The Netherlands: Centraalbureau voor Schimmelcultures: Institute of the Royal Netherlands Academy of Arts and Sciences.
  16. ↑ Mdaini, N; Gargo, M; Hammami, M; Monser, L; Hamdi, M (2006). "Production of Natural Fruity Aroma by Geotrichum candidum". Applied Biochemistry and Biotechnology. 128: 127–136. doi:10.1385/abab:128:3:227.
  17. 1 2 3 Moore-Landecke, Elizabeth (1972). Fundamentals of the Fungi. Englewood Cliffs, N.J.: Prentice-Hall Incorporated. ISBN 0-13-339267-8.
  18. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Rippon, John Willard (1988). Medical Mycology : The Pathogenic Fungi and the Pathogenic Actinomycetes (3rd ed.). Philadelphia, PA: Saunders. ISBN 0721624448.
  19. 1 2 3 4 5 6 7 Moss, Emma Sadler; A.L McQuown (1969). Atlas of Medical Mycology (3rd ed.). Baltimore,Md: The Williams & Wilkins Company. ISBN 978-0683060867.
  20. 1 2 3 4 5 6 Webser, B. H. (1 March 1959). "Bronchopulmonary Geotrichosis: A Review with Report of Four Cases". CHEST Journal. 35 (3): 273–281. doi:10.1378/chest.35.3.273.
  21. ↑ Bell, D; Brodie, J; Henderson, A (1962). "A Case of Pulmonary Geotrichosis". Chest. 56 (26): 26–29. doi:10.1016/s0007-0971(62)80031-x.
  22. 1 2 Vázquez-González, Denisse; Perusquía-Ortiz, Ana María; Hundeiker, Max; Bonifaz, Alexandro (2013). "Opportunistic Yeast Infections: Candidiasis, Cryptococcosis, Trichosporonosis and Geotrichosis". JDDG: Journal der Deutschen Dermatologischen Gesellschaft. 11 (5): 381–394. doi:10.1111/ddg.12097.
  23. 1 2 3 Pottier, I.; Gente, S.; Vernoux, J. P.; Gueguen, M. (2008). "Safety Assessment of Dairy Microorganisms: Geotrichum candidum". International Journal of Food Microbiology. 126: 327–332. doi:10.1016/j.ijfoodmicro.2007.08.021.
  24. ↑ Pal, M.; Sejra, S.; Sejra, A.; Tesfaye, S. (2013). "Geotrichosis: An Opportunistic Mycosis of Humans and Animals". International Journal of Livestock Research. 3 (2): 38–44. doi:10.5455/ijlr.20130525092525.
  25. ↑ Marcellino, N; Beuvier, E; Grappin, R; Gueguen, M; Benson, D.R (2001). "Diversity of Geotrichum candidum Strains Isolated From Traditional Cheesemaking Fabrications in France". Applied and Environmental Microbiology. 67 (10): 4752–4659. doi:10.1128/aem.67.10.4752-4759.2001.

Structure based design of novel inhibitors for histidinol dehydrogenase from Geotrichum candidum.Pahwa S, Kaur S, Jain R, Roy N.,Bioorg Med Chem Lett. 2010 Jul 1;20(13):3972-6, PMID 20488699

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