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Sakinaka3/sandbox
Scientific classification
Kingdom:
Fungi
Division:
Ascomycota
Subdivision:
Pezizomycotina
Class:
Sordariomycetes
Subclass:
Sordariomycetidae
Order:
Sordariales
Family:
Cephalothecaceae
Genus:
Phialemonium
Species:
P. obovatum
Binomial name
Phialemonium obovatum
Gams, W. & McGinnis, M.R. (1983)

Phialemonium obovatum is a saprotrophic filamentous fungus able to infect humans, especially those with weakened immune systems.[1][2][3] Phialemonium species are widespread throughout the environment, occuring commonly in sewage, soil, air and water.[1][2] Walter Gams and Michael McGinnis described the genus Phialemonium to accommodate species intermediate between the genera Acremonium and Phialophora.[2][4][5][6] Currently three species of Phialemonium are recognized of which P. obovatum is the only one to produce green colonies and obovate conidia.[7]

Growth and morphology

In culture, colonies of P. obovatum begin as white or off-white in colour becoming pale green and centrally darkened with age.[8][1] The green pigments diffuse in the growth medium ultimately becoming blackish-green in colour.[1] Although the hyphae of the fungus are typically colourless (hyaline), the presence of these dark pigments has cause this and other species of Phialemonium to be considered amongst the dematiaceous fungi.[8] This placement may be further justified by the confirmation of melanin pignments in hyphal walls and septa as demonstrated by Fontana-Masson's staining procedure.[6][2] These pigments of melanin in cell walls of hyphae and conidia were found to be the reason for the dark colours seen in the center of the colonies.[8]

Gams and McGinnis described P. obovatum as having a flat, smooth colony texture with hyphal strands that radiate outwards described as floccose (fluffy or cottony).[4] Colonies of this species appear moist and lack a distinctive odour.[4] The fungus produces droplets of smooth-walled, obovate conidia with a narrow base. Their shape is similar to a tear drop or an egg-like shape.[1][6][7] Phialemonium obovatum conidia arise from adelophialides (phialides lacking a a basal septum) which do not have collarettes.[4][7][6] Conidia are typically produced only at the interface of the medium surface and the air, and are rarely present on submerged hyphae or aerial hyphae.[4][7] Phialemonium obovatum grows optimally between 24–33 °C (75–91 °F) although it can grow at temperatures as low as 15 °C (59 °F) and as high as 40 °C (104 °F).[4]

Pathogenicity

Saprophytic species are generally pathogenic to plants, as the name implies. However, more and more of these species are seen as causes of human infections. Phialemonium obovatum is a type of saprophytic dematiaceous fungi that can cause infections in the human hosts it invades [6] [1] [2] [9]. While there may be some animals that are infected, most cases of infections have been reported in humans [6] [1] [2] [9]. Some of these infections include (fatal) endocarditis, keratitis, peritonitis, osteomyelitis, subcutaneous infections, and infections caused by burns [6] [1] [2] [9]. The commonality this fungi shows when causing infections is that it does not infect all humans but majorly those who are immunocompromised (i.e. those with weak immune systems). Thus it is labelled as an opportunistic fungi however, it can also target immunocompetent hosts as well (i.e. those with normal immune systems)[2] [1] [6] [7]. And for this reason, it is said that as numbers of immunocompromised patients increase, there is set to be an increase in the emergence of pathogenic fungi as well [6]. More specifically, it has been shown that dematiaceous fungi such as Phialemonium obovatum are becoming a greater cause of infections in people who receive transplants because these people have to suppress their immune systems for the body to accept transplanted organs[9] [6]. This allows species such as Phialemonium obovatum an opportunity to develop infections. Therefore, it can be deduced that Phialemonium species in particular may develop into a more common pathogenic fungi.[6]

Phialemonium obovatum’s ability to infect humans is due to its ability to grow at body temperature which makes it pathogenic. Generally, pathogenicity tests are completed by measuring the temperatures fungi can withstand.  Dematiaceous species can withstand temperatures at 35°C which means they can be invasive to human tissue and are likely to spread as it is near body temperature [6]. Furthermore, it has been shown that Phialemonium obovatum species can grow at temperatures as low as 15°C and as high as 40°C, with their optimum growth being in between 24°C-33°C [4]. Since this species has shown that their ability to grow at temperatures of up to 40°C, they can easily be an invasive pathogenic fungi. Additionally, this ability also allows them to infect the central nervous system [6].

Being able to grow in the body is only one aspect of being infectious; the other aspects include how it spreads and what factors it has that cause it to be virulent rather than harmless. Some research suggests that melanin pigments found in cells walls have antioxidant properties which can serve as virulence factors[6] . In case studies involving infections following severe burns, researchers have found that Phialemonium obovatum's hyphae have the ability to invade into blood vessels and tissues[7]. Other case studies revealed yeast-like cells in the blood of infected individuals. Therefore, once invaded, Phialemonium obovatum can disseminate, colonize, and infect different places [6]. Some cases have proven to be fatal [6].

Potential uses

The aging process of wine in wooden barrels is a traditional process used to enhance the richness of wine. However, this method is expensive for winemakers as preparing wine barrels is a costly and time consuming process. The wooden barrels undergo biochemical changes and develop mycotic infections in order to produce compounds to create a rich taste in wine. This entire process is a preparation of wooden barrels which takes upwards of 36 months alone. Wine makers have considered the use of wood chips an alternative to barrels to produce the wine’s flavour and aroma. Using this method can also speed up the aging of the wood[10][11]. This therefore led researchers to consider the use of oak chips inoculated with fungi including Phialemonium obovatum in order to observe their effects on the composition of wine[10]. If the oak chips are inoculated with certain fungi, researchers can control what enzymes the wood is exposed to thus they are capable of manipulating its effect on wine. Additionally, this process can increase the aging process of the wood with the enzymes that the inoculated fungi produces.[10]

Furthermore, researchers inoculated oak chips with different fungi. They used oak chips of different sizes, and in different types of environments in order to favour the fungus. Those chips were then used to age the wine and then concentrations from different compounds that are present in wine were extracted and measured. The results showed that the species of fungi they used and different treatment conditions of the oak chips affected the presence and concentrations of different phenolic and volatile compounds in wine.[10][11]

The wine which contained oak chips treated with Phialemonium obovatum as well as other fungi showed an increase in the concentrations of syringol and guaiacol compounds. Syringol is a compound that is produced when the wood is toasted thus it indicating the degree to which the wood is toasted. Guaiacol, on the other hand, is synthesized when wood is being toasted and lignin is breaking down. It produces a burnt-like aroma in the wine. Guaiacol has a greater effect than syringol on the flavour of wine.[10][11]

This research has shown that the presence of fungi can affect the flavour and composition of wine. Furthermore, with the use of inoculated oak chips one can speed up the aging process but more importantly, the use of inoculated oak chips allow one to customize the composition of wine to one’s taste[10] [11].  This research is still in its early stages even though it seems promising in its potential applications. Although researchers mentioned that they used non-mycotoxigenic fungi throughout their paper, this method does raise controversial issues regarding the toxicity of some fungi[10].

References

  1. ^ a b c d e f g h i Hong, Kwon Ho; Ryoo, Nam Hee; Chang, Sung Dong. "Phialemonium obovatum Keratitis after Penetration Injury of the Cornea". Korean Journal of Ophthalmology. 26 (6). doi:10.3341/kjo.2012.26.6.465. PMC 3506823. PMID 23204804.
  2. ^ a b c d e f g h Perdomo, H.; Sutton, D. A.; García, D.; Fothergill, A. W.; Gené, J.; Cano, J.; Summerbell, R. C.; Rinaldi, M. G.; Guarro, J. (2011-04-01). "Molecular and Phenotypic Characterization of Phialemonium and Lecythophora Isolates from Clinical Samples". Journal of Clinical Microbiology. 49 (4): 1209–1216. doi:10.1128/JCM.01979-10. ISSN 0095-1137. PMC 3122869. PMID 21270235.
  3. ^ "Phialemonium obovatum". www.cbs.knaw.nl. Retrieved 2015-10-17.
  4. ^ a b c d e f g Gams, Walter; McGinnis, Michael R. (1983-11-01). "Phialemonium, a New Anamorph Genus Intermediate between Phialophora and Acremonium". Mycologia. 75 (6): 977–987. doi:10.2307/3792653.
  5. ^ "Phialemonium obovatum". www.mycobank.org. Retrieved 2015-11-17.
  6. ^ a b c d e f g h i j k l m n o p Gavin, Patrick J.; Sutton, Deanna A.; Katz, Ben Z. (2002-06-01). "Fatal Endocarditis in a Neonate Caused by the Dematiaceous Fungus Phialemonium obovatum: Case Report and Review of the Literature". Journal of Clinical Microbiology. 40 (6): 2207–2212. doi:10.1128/JCM.40.6.2207-2212.2002. ISSN 0095-1137. PMC 130710. PMID 12037088.
  7. ^ a b c d e f McGinnis, Michael R.; Gams, Walter; Goodwin, Malcolm N. (1986-01-01). "Phialemonium obovatum infection in a burned child". Journal of Medical and Veterinary Mycology. 24 (1): 51–55. doi:10.1080/02681218680000061. ISSN 0268-1218.
  8. ^ a b c Brandt, M.e.; Warnock, D.w. (2003-01-01). "Epidemiology, Clinical Manifestations, and Therapy of Infections Caused by Dematiaceous Fungi". Journal of Chemotherapy. 15 (Supplement-2): 36–47. doi:10.1179/joc.2003.15.Supplement-2.36. ISSN 1120-009X.
  9. ^ a b c d Thomas Clark, MD; Gregory D. Huhn, MD; Craig Conover, MD; Salvatore Cali, MPH; Matthew J. Arduino, DrPH; Rana Hajjeh, MD; Mary E. Brandt, PhD; Scott K. Fridkin, MD (2006-11-01). "Outbreak of Bloodstream Infection With the Mold Phialemonium Among Patients Receiving Dialysis at a Hemodialysis Unit •". Infection Control and Hospital Epidemiology. 27 (11): 1164–1170. doi:10.1086/508822.
  10. ^ a b c d e f g Petruzzi, Leonardo; Bevilacqua, Antonio; Ciccarone, Claudio; Gambacorta, Giuseppe; Irlante, Giuseppina; Pati, Sandra; Sinigaglia, Milena (2010-12-01). "Use of microfungi in the treatment of oak chips: possible effects on wine". Journal of the Science of Food and Agriculture. 90 (15): 2617–2626. doi:10.1002/jsfa.4130. ISSN 1097-0010.
  11. ^ a b c d "Using Fungi-Treated Oak Chips to Increase the Extraction of Oak Character into Aging Wines". The Academic Wino. Retrieved 2015-11-17.
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