Fungi examples Flashcards
humongous fungi
Amillaria species.
true pathogen
biomass under soil and attacks roots of tree.
100tonnes of biomass
over15000 years old.
Yeast
Saccharomyces cerevisae (balers yeast)
Schizosaccharomyces pombe (a model laboratory organism)
agent that causes thrush
Candida albicans
Ascomycetes examples
‘Saccharomyces cerevisiae’ was the first eukaryotic genome to be sequenced and work performed using ‘Neurospora crassa’ was awarded the Noble prize for the proposal of “one gene one protein” hypothesis
plant pathogens in this group; for example, ‘Claviceps’ and ‘Erysiphie’ species.
basidiomycetes examples
lignin decomposes (Serpula lacrymans is dry rot). They are important food sources in the form of mushrooms
(Agaricus bisporus is the common mushroom found in the UK).
They are also important crop pathogens including Puccinia species which causes rust disease – the brown marks are necrosis of cells which gives the appearance of rust.
deuteromycetes examples
important food spoilers (Aspergillus flavus) and the industrial workhorse, ‘Aspergillus niger’ for the production of medicines and foodstuffs
What is aflatoxin produced by
Aspergillus flavus) to protect its food source
true pathogen disease and pathogen example
Histoplasmosis
pathogen is Histoplasma capsulatum
Most common in the USA and leads to less than 50 deaths per year. In the filamentous form, it appears as a brown colony on the growth plate and at 37 Celsius it converts to a white waxy yeast form. The spores (from the filamentous form) have small appendages on them that help them to be dispersed by the wind.
The infection cycle starts mainly from bird droppings, the spores are easily inhaled and the infection is local to the lung. In the lung, the spore grows as a yeast which then forms endospores and the cycle of infection continues. In most cases the phagocytes are able to limit and remove the infection however, if the infection spreads it can affect the heart lung and liver tissues and become fatal.
True pathogen example and pathogen alkaline example.
coccidiodiomycosis caused by Coccidioides immitis.
It is most common in alkaline soils of the southwest of the USA. Most cases are asymptomatic but it can lead to fever in approximately 40% of infections. It produces arthrospores and these are the infectious agent. In the body, they grow as sporangia and release spores in the lung and leads to infection which is usually cleared by the immune system.
If the host is immunocompromised then it can cause complication leading to meningitis and rashes. However, it is generally well controlled by the host cell.
Examples of opportunistic pathogen.
Aspergillus fumigatus, they are isolated from compost heaps which are very warm and of course the host is running at high temperature and Aspergillus fumigatus is adapted to that temperature from its natural environment. They can cause a range of severity of infection up to chronic systemic infection and the prognosis (likely course uncertain) in this case is very poor! The mortality rate is high. Causes aspergillosis.
produces mycelium in the lung called an aspergilloma.
Candida albicans that causes candidiasis or thrush(common in babies).
(20% of us carry it as a commensal organism)
dermatophytes example
ring worm caused by the Trichophyta species which also cause athletes foot
pathogens of immature tissue example
Pythium and Phytothphora genera which are actually oomycetes – they were originally classed as fungi but with modern molecular techniques they are more closely related to algae and have been reclassified as protists). They aggressively invade the roots tips (the new cells have weaker cell walls and are the site of infection) and are associated with water-logged soils and they are known as damping-off diseases. The infection cause necrosis of the root tip and stunt growth
necrotrophic pathogen of mature tissue example
necrotrophic pathogen of mature tissue is the honey fungus (Amillaria mellea). It is a major root pathogen of broad leaved trees. It uses rhizomorphs to attack the plant and target the phloem tissue
biotrophic pathogen of mature tissue example.
Ersyphie graminis and Puccinia graminis that infect wheat species
maintain the host cell viability – they do not kill the plant but compromise the growth of the plant. They have limited tissue invasion and the infection does not evoke a resistance mechanism (i.e. the plant is not aware of the infection!)
Erysiphie, the infection is in the epidermis of the leave and they produce these haustoria in these cells. In both cases the infection hyphae “punch” a hole in the cell wall of the infected cell!
controlling insect pests examples
Mycotal (for whitefly and thrips) and Vertalec (for aphids) and they are different formulations of the same fungal species spores.
fungus is Verticllium lecanii and the difference between the formulations is the addition of oil to Vertalec, which enables more efficient infection of aphids
can produce spores in liquid fermenter
spores are produced at the ends of specialised hyphal cells
germinate in high relative humidity and at a strict temperature range making suitable for glasshouses only.
fungi that parasites other fungi examples
oomycete, Pythium oligandrum. It targets the host cell Botrytis cinerea (which is a prominent infection on grapes)
Trichoderma species have been marketed for this approach. They produce toxins (e.g. gliotoxin) which is effective against other fungal species and thus can be used to control phytopathogenic fungi. It is currently marketed as Trianum by Koppert. The approach here is that bran is used in the formulation to act as a food source for Trichoderma and the Trichoderma produces antibiotics to protect the food source and thus is effective at controlling growth of fungi that parasitize the plant.
example of using competition between fungi to control a fungal infection that causes butt rot.
pathogenic fungus is Heterobasidium annosum and it infects the stumps from a felled tree and using this as a platform to attack and parasitize surrounding tree
stump is infected with a saprophytic fungus, Phlebiopsis gigantea. The Phlebiopsis species growth and is effective in out competing the parasitic fungus for nutrient and thus prevents the infection of the stump and the growth of Heterobasidium from attacking surrounding trees and producing more spores.
prominent yeast used in the brewing and baking industries
Saccharomyces cerevisiae
fungi helps produce soy sauce
beans are fermented using Aspergillus oryzae which releases nutrients which are then available for human digestion
beans are soaked and then cooked for 16 hours before fermentation with Aspergillus oryzae (the time of fermentation is an issue of quality) and then salt is added to 20% before a further anaerobic fermentation by the halotolerant yeast, Zygosaccharomyces rouxii. The time spent fermenting is an issue of quality. So two fungi are used in this process. The end product is filtered and bottled
quorn is a mycoprotein
hyphae of Fusarium graminearium (reclassified as venenatum)
grows cheaply on glucose syrup and ammonia and then the filaments are spun to resemble muscle fibers
work house of fungal world
Aspergillus niger
production of pectinases: these enzymes breakdown pectins in the plant cell wall. These enzymes clarify fruit juices. Glucose oxidases are used in food preservation: it oxidises glucose to gluconate and hydrogen peroxide and the removal of oxygen and the production of hydrogen peroxide in the reaction are the basis of food preservation. The enzyme is also very specific for glucose and this property is used to detect glucose in urine (used as a dipstick test on urine samples by the doctor) – the colorimetric test relies on the production of hydrogen peroxide and if positive it indicates a kidney problem! Finally, the phytases are used to improve animal feed. Plants store phytic acid in their vacuole as a source of phosphate. This is not easily digested and so pretreatment of the animal feed with phytases helps to release nutrients
produce glucoamylases which are enzymes used to convert starch to an edible high glucose syrup which is used in the food industry
almost all citric acid comes from Aspergillus niger cultures
production is based on the citric acid cycle and in this cycle there is a conversion of citrate to aconitate by the enzyme aconitase
fungi examples to produce drugs
penicillin
fungus is Penicillium notatum
synthetic forms of penicillin to day (e.g. methicillin and ampicillin)
