block C - fungi Flashcards
what are some characteristics of fungi?
theyre mostly multicellular
theyre eukaryotic
spores or resting bodies can sometimes be produced
what are hyphae?
they’re the ends of branching filaments and hyphae that extend above the surface can produce asexual spores called candida
hyphae form compact tufts called mycelia
what are most fungal cell walls made of?
chitin, the second most abundant biopolymer on the planet
what does mycorrhizae help with?
it helps plant roots obtain phosphorous
what are candida resistant to?
they’re often resistant to drying and are often pigmented
why do fungal cells produce spores?
they produce them in response to cell density or to search for nutrients
theyre really dispersal agents and allow the organim to disperse and spread
why do fungal cells often have hydrophobic outsides and grow from the tip?
it allows them to forage and branch in order to achieve exponential growth and form a network of hyphae
what are fruiting bodies?
theyre macroscopic reproductive structures and examples include mushrooms and puffballs
what is an example of a disease caused by fungi?
mycoses in humans causes athletes foot in the least serious cases and histoplasmosis in the most serious cases
what type of infection will 40% of people on life support die from?
candida infections
why do fruit bodies exist?
theyre a dispersal mechanism to release spores into the enviroment
what way do most fungi reproduce?
asexually
what are the three ways fungi can asexually reproduce?
- growth + spread of hyphal filaments
- asexual production of spores
- simple cell division (budding yeasts)
what ways can fungi reproduce sexually?
- sexual spores can originate from the fusion of 2 haploid cells to form a diploid cell
- spores (are resistant to drying, heating, freezing and chemicals)
what happens in a budding yeast cell when it reproduces?
the mother cell replicates its genome then the daughter cell closes off and grows until its almost the same size as the mother cell, where it buds off
how can you estimate the age of a yeast cell?
by how many bud scars it has
why are yeast a good model organism for ageing and gene research?
theyre very easy to introduce DNA into and theyre eukaryotic
fungi and animals diverged the latest from other eukaryotic cells, how long ago did they diverge form one another?
1.5 billion years ago
what are the key genera of chytridiomycetes?
allomyces and batrachochtrium
where are chytridiomyces commonly found?
in moist soil and freshwater
what problems with wildlife have chytridiomycetes caused?
theyve been implicated in massive die-offs of amphibians
what can all zygomycetes form?
zygospores
what do microspirida often infect?
they often infect immune-compromised individuals e.g. immune comromised individuals
what do all known species of glomeromycetes form with the roots of herbaceous plants?
endomycorrhizae
in some cases theyre also formed with woody plants and theyre essential for plant growth
why are glomeromycetes thought to have played an important role in the ability of early vascular plants to colonise the land?
they can solubilise phosphate and other nutrients and are able to utilise the carbon that plants have
what are the key genera of ascomycetes?
saccharomyces
candida
aspergillus
how can yeast cells switch from one mating type to another?
by a genetic switch mechanism
what are silent versions of yeast cells?
it means they have no promoter
what does the mating type switch facilitate in yeast cells?
it facilitates genetic interaction and swapping genes between organisms
what are the key genera of basidiomyces and what are they often described as?
agaricus, amanita
they’re often described as mushrooms or toadstools
there are over 30,000 described species
what type(s) of reproduction do basidiomycetes undergo?
vegetative and sexual
what is hyphal growth?
its basically the only way to grow exponentially through branching by more branches branching fom the newly formed branches
what is the spitsenkorper?
its the end of the branch
why are fungi important?
they’re one of the most important groups of organisms for nutrient cycling on a global scale
significant human and animal pathogens are fungal
biotechnologically and industrially important
what are the uses of fungi in medicine?
- antifungal drugs
- antibacterial drugs
what are microbial natural products?
theyre chemicals produced by microorganisms in nature as they give the microorganisms an adaptive advantage for resources and/or space
what is the problem with antifungal agents?
they target cellular processes that universally affect both humans and fungi because both of them are eukaryotic so this can lead to toxicity issues
what are primary metabolites?
theye stuff essential for life e.g. amino acids
what are secondary metabolites?
theyre stuff that help the cells in competition like antimicrobials
can fungi be pathogenic and cause disease?
yes
what does mycosis mean?
it means any infection caused by a fungus/ growth of a fungus on/in the body
who is most likely to get fungal infections?
immunocompromised people, normal healthy people arent likely to develop fungal infections
what are the range of seriousness that fungal infections can become?
they range from superficial, mild or self limiting infections like athletes foot all the way to systemic infections that reach the deepest of internal tissues and can become life threatening
how many species of fungi can cause disease in humans?
about 50
how can you detect that you have a fungal infection?
by studying the morphology of spores under the microscope for identification/ diagnosis along with molecular and immunological tools
what are the three main ways fungi can cause disease?
- inappropriate immune response (exposure to fungi causing allergic responses
- toxins (this is called myotoxins)
- host infection (this is called mycoses)
name a toxin produced by fungi and what does it do?
aspergillus produces toxins, the alphatoxin group is the most common, its highly toxic and carcenogenic, especially to birds
it also causes human diseases including cirrhosis (liver damage)
what does superficial mycosis affect?
it means the fungus only affects the surface layer of skin, hair and nails
why is superficial mycosis mostly treatable?
its mostly treatable with topical antifungal creams or liquid aerosols because fungi are eukaryotes and so are we so if you’re targeting other eukaryotes, youre also targeting your own cells
what are fungi that cause superficial mycoses collectively called?
dermatophytes
what does richophyton spp. cause?
fungal; infections of the feet and other moist surfaces
transmission is by spores that can be released by flaking and itching of skin
what is subcutaneous mycosis?
its a fungal infection that affects the deeper layers of skin
what are subcutaneous mycosis commonly caused by?
they’re caused by different fungi than superficial infections and sometimes the fungi can get under the skin through a cut
what can subcutaneous mycosis be treated by?
topical drugs
theyre often treated with oral administration of azole antifungal agents
what is Sporotrichosis caused by?
caused by the saprophyte Sporothrix schenckii
how can you get infected with sporotichosis?
occupational hazard of those working in close content with soil agriculture workers, miners, gardeners (spores can enter through cut skin)
what is chromoblastomycosis caused by?
caused by several species (Fonsecaea pedrosoi, Phialophora verrucose, Cladosporium carrionii, Fonsecaea compacta)
what are the symptoms of chromobastomycosis?
Fungal growth both subcutaneous and cutaneous (surface)
Form crusty wart like lesions on hand or leg
Tropical / subtropical conditions – fungus infection from puncture wound
what is systemic mycosis?
its fungal growth that affects internal organs
how are you usually infected with systemic mycosis?
the pathogens normally live in soil and the nfcetion of humans is due to them inhaling spores
then it travels from the lungs to other organs and skin
who does systemic mycosis primarily affect?
people going through chemotherapy, the elderly and the otherwise immunocomprimised
the older you get, the more cell mediated immunity declines
immune system impared/ destroyed- HIV/ AIDS
what does it mean by ‘systemic mycoses are diseases of oppturnistic pathogens’?
it means they only cause disease in those whose immune defense can no longer fight off the fungi
what are primary fungal diseases?
they happen when healthy individuals are infected
what are secondary fungal diseases?
they happen when a predisposing condition makes the individual more susceptible to infections such as antibiotic therapy or immunosupression (therapy and HIV-AIDS)
what are some examples of systemic mycosis?
- histoplasmosis
- coccidioidomycosis
- blastomycosis
what is histoplasmosis?
its a fungal infection caused by histoplasma capsulatum
its one of the most widespread primary fungal infections and is found in midwest US
its spread by inhaled spores that germinate and then grow in the lung
what is coccidioidomycosis?
its caused by coccidioides immitis and is found in desert regions of south west US
it causes respiratory symptoms and is a cause of pneumonia
what is blastomycosis?
its a fungal disease caused by blastomyces dernatitides and is endemic to areas in north america
the fungus lives in rotten wood and soil near bodies of water and causes a lung infection
if left untreated, very late in the disease, it causes skin lesions
what is paracoccidioidomycosis?
its caused by Paracoccidioides brasiliensis and is primarilt a subtropical disease and is potentially aquatic
initially its a pulmonary infection then lesions form on the face
what is azole treatment?
its a type of antifungal that can be used to treat fungal infections of the body and skin, including athlete’s foot, onychomycosis (fungal nail infections), ringworm, and vaginal candidiasis.
what is cryptococcosis?
its caused by the yeast form of Cryptococcus neoformans and can occur anywhere in the body and is an opportunistic pathogen so it is seen a lot in HIV-AIDS patients
what is candida albicans?
its a dimorphic yeast often present as a minor component of human normal flora
it can form biofilms which can be difficult to treat with antifungal agents
they can form mild to serious infections, depending on the immune levels in the patient
what is pneomocytosis?
- pneomocytosis pneumonia is often caused by pnemocytosis jiorvecil
- is an oppturnistic infection in immunoupressed people (like chemotherapy+ AIDS patients, premature + severely malnourished children, elderly and infants with hyper IgM syndrome, an x-linked or autosomal recessive trait)
what are ergosterol inhibitors?
theyre basically the only type of antifungal treatment and they target the analogue of cholesterol in fungal plasma membranes which provide stability and shape maintenance
what are the two main classes of ergosterol inhibitors?
polyenes
azoles
what is the mode of action for ergosterol inhibitors?
they target the unique fungal plasma membrane component, bind to ergosterol and destabilise fungal cell membranes to lead to cell death
what is the structure of polyenes?
they are molecules with multiple conjougated double bonds which contain at least three alternating double and single carbon-carbon bonds
what is the mechanism of action of polyenes?
they bind to sterols in the fungal cell membrane, principally ergosterol
this takes place in the membrane in a less fluid, more crystaline state
small organic molecules leak from the cell include noncovalent ions resulting in cell death
what are the three main classes of azoles?
imidazoles
triazoles
thiazoles
what is the mode of action for azoles?
they inhibit the enzyme lanosterol 14-alpha-demethylase which converts lanosterol to ergosterol
depletion of ergosterol in fungal membrane disrupts the structure and many functions of fungal membranes/ accumulation of toxic sterol intermediated leading to inhibition of fungal growth
why, if there’s a limited supply of ergosterol precursor does the cell break down?
if theres a limited supply of the precursor becuase of the azole, you cant make much ergosterol which means the cell membrane rigidity breaks down and the cell dies
what are echinocandins?
theyre a new class of antifungal drugs that inhibit the synthesis of glucan in the cell wall
what is the mechanism of action for echinocandins?
they inhibit the synthesis of glucan in the cell wall via inhibition of the enzyme 1,3-beta-glucan synthease
beta-glucans are carbohydrate polymers that are cross-linked with other fungal cell wall components, this inhibition prevents fungal wall synthesis
depletion of glycan polymers leads to weakened cell wall and osmotic stress
what are DNA synthesis inhibitors?
theyre nucleic acid analogues that mimic cellular nucleotides
what is the mechanism of action for DNA synthesis inhibitors?
they inhibit enzymes required for DNA synthesis
what types of infections can be treated with DNA synthesis inhibitors?
minor infections like candidial cystits
if it was flucytosine, candida infections and crytococcus neoformans- they would be used in combination with amphotericin B and/or azole antifungals such as fluconazole, relatively weak antifungal effects and fast development of resistance
what are mitosis inhibitors’ modes of action?
interfering with fungal mitosis (disruption of microtubule aggregation)
what is an example of a mitosis inhibitor?
griseofluvin is a relatively non-toxic drug that can be taken orally but passes through thr bloodstream to the skin
what are the beneficial applications of fungi?
- antibiotics
- food industry
- agriculture
- bioremediation
- research
- other bioactive metabolites
what are natural products?
they’re things that are produced by cells ect naturally
what does the term ‘semi-synthetic’ mean?
it is stuff that is made by bacteria and then is slightly modified by scientisits
what are fungal natural products?
they’re microbial metabolites produced by fungi
why is anti-microbial resistance important?
its naturally inherent and drives new chemical discovery
what is beta-lactam?
it comes from natural and semi-synthetic sources
and its one of the most important groups of antibiotics
what is the mode of action for beta-lactams?
theyre inhibitors of bacterial cell-wall synthesis and irreversible binding to PBPs to prevent transpeptidation (the cross-linking of peptidoglycan)
what is the name of the ring structure in beta lactams that causes them to work effectively?
thaizolidine ring
what is the name of the ring structure in beta lactams that causes them to work effectively?
thaizolidine ring
what is penicillin resistant to beta-lactamase-methicillin flucloxacillin used to treat?
staphylococcal infections but not MRSA as its not sensitive
what does penicillin G target?
it targets most gram-positive bacteria and some gram-negative cocci such as staphylococcal and pneumococcal infections
what is the mode of action for penicillin G?
it inactivates the penicillin binding proteins (PBPs) located within the bacterial cell wall and interferes with cross linking of peptidoglycan, causing weakening and cell lysis in the end
what are narrow spectrum antibiotics?
they’re antibiotics that only target a specific type of bacteria
what is cepalosporins produced by?
theyre produced by the fungus acremoium
how does cefoxitin work and what does its activity spectrum include?
it acts by interfering with cell wall synthesis and its activity spectrum includes a broad range of gram-negative and gram positive bacteria including anaerobes
what are echinocandins?
theyre a new class of antigungals which inhibit the synthesis of glucan in the cell wall
how do echinocandins work?
they inhibit the synthesis if glucan in the cell wall via inhibition of the enzyme 1,3-beta-glucan synthase. beta glucans are carbohydrate polymers that are cross-linked with other fungal cell wall components
this inhibition prevents fungal cell wall synthesis
where do echinocandins come from?
they come from semi-synthetic from pneumocandin Bo (natural cyclic lipopeptide)
where does caspofungin come from?
its a semi-synthetic antifungal that is derivative from a fermentation product of the fungus glarea lozoyensis
what is the structure of a caspofungin and what are their clinical applications due to?
its a lipopeptide - an acetate salt of an antimycotic echinocandin lipopeptide
their clinical applications are due to their solubility, antifungal spectrum and pharmacokinetic properties, its administered intravenously
what is the target of a caspofungin?
their targets are fungal infections caused by aspergillus and candida sp.
what is the target of micafungin?
its the treatment of candidemia , candida peritonitis, abcesses and esophageal candidiasis
what is the genral structure of micafungin?
its a cyclic lipopeptide
how is micafungin administered?
intravenously
what is the source of micafungin?
it is a semi-synthetic compound derived firm a natural product of the fungus coleophama empedri
what is the mode of action for micafungin?
it non-comptitively inhibits the fungal specific enzyme 1,3-beta-D-glucan synthase (this controls cell wall synthesis)
what is the target if andiulafungin?
candida and aspergillus
what is the general structure of an anidulafungin?
its a cyclic lipopeptide echocandin derivative
what is the mode of action for anidulafungin?
it inhibits 1,3-beta-D-glucan synthase (this controls fungal cell wall synthesis)
what is the source of aniulafungin?
its a semi-synthetic compound called achocandin B (a lipopeptide fermentation product of aspergillus nidulans and undergoes decylation by the action of deacylase enzyme from the bacterium actinoplanes utahensis)
i think the only part you actually need to know is that its semi-synthetic
what is the mode of action for mitosis inhibitor antifungals?
they interfere with fungal mitosis (disruption of the microtublule aggregation)
what is the target of mitosis inhibitor antifungals?
they’re used to treat a number of different types of dermatophytosis (ringworms)
this includes fungal infections of the skin and nails when antifungal creams don’t work
what is the source of mitosis inhibitor antifungals?
they come from the fungus penicillium Griseofulvin
what are some other bioactive metabolites?
statins, immunosupressants and drugs
what microorganisms produce statins?
Aspergillus terreus and oyster mushroom produce lovastatin
Penicillium citrinum produces mevastatin
Both statins lower blood cholesterol levels preventing problems of the circulatory system (e.g. atherosclerosis)
what microorganism produces immunosupressants?
Tolypocladium inflatum produces cyclosporine
Used for rheumatoid arthritis, psoriasis, Crohn’s disease, nephrotic syndrome, and in organ transplants to prevent rejection
how are fungi involved in cheese production?
fungi from the genus penicillium ripen many cheeses
they originate in the natural enviroment and are responsible for the taste and the veins
Penicillium roqueforti or Penicilliun glaucum are used for the production of blue cheese: Roquefort, blue stilton, Lanark blue
Penicillium candidum and Penicillium camemberti are used for the production of brie and camembert
what fungus is quorn made form?
Fusarium venenatum
what is yeast extract made from?
saccharomyces cerevisiae
what is bakers yeast?
its saccharomyces cerevisiae and it undergoes fermentation to produce CO2 and helps dough rise
what does yeast do in alcohol production?
it turns sugar into alcohol
what id citric acid made from?
aspergillius sp.
its widely used as an acidifier as a flavoiuring and a chelating agent
what is acetic acid?
its a food additive made by various species of yeast
its also an important chemical reagent and inducstial chemical
what are examples of things made with acetic acid?
vinegar
production of cellulose acetate for photographic film
polyvinyl acetate for wood glue
synthetic fibres and fabrics
diluted acetic acid is often in descaling agents
what is bioenthanol?
its an alternative energy source to petroleum-based fuels
its made by saccharomyces cerevisiae which has been genetically engineered to ferment xylose, one of the major fermentable sugars in cellulosic biomasses such as agriculture residues, paper wastes and wood chips
how are fungi used in biological control?
they naturally produce microbial insecticides and help to control the population of damaging pests, theyre very specific to the insect/ mite/ nematode they attack and dont infect other animals or plants. this also means synthetic chemical use is reduced
what are some examples of biological control fungi?
The fungusBeauveria bassianaproduces a pesticide against emerald ash borer
Metarhizium spp., Hirsutella spp., Paecilomyces (Isaria) spp., and Lecanicillium lecanii.
how do fungi help with soil fertility?
they live in the roots of plants and help to transfer water and nutrients
its a mycorrhixal relationship and is essential for the productivity of farm land, without this, 80-90% of trees and grasses would die
what is bioremediation?
uses micro-organisms to reduce pollution through the biological degradation of pollutants into non-toxic substances
what do white and brown rot fungi do?
white - they digest moist wood
brown - they digest dead wood
these fungi can be used for alternative production of energy from cellulosic biomass and enzymes that are involved in these processes are considered very interesting for the bioenergy industry
what is biodegradation?
its the removal of oil spills and heavy fuels in the sea
fungi can utilise their long chain hydrocarbons
what toxic chemicals can fungi remove from the soil or water?
insecticides
heribcides
uranium oxidies
why have yeast been studied as model microorganisms?
they’re simple eukaryotic organisms and saccharomyces served as the starting point to discovering analogues of human genes
they produce and modify proteins in a similar way to human cells and make a good organism for being used in recombinant DNA technology experiments
they’re also easy to culture and have a short half life
how have yeast cells been used in gene libraries?
they were originally the cells used in the human genome project because of their artificial chromosomes but they were then replaced by bacterial cells as they had plasmids
why are yeast cells used in drug testing?
- share many genes with humans, so thye can be used for screening if drugs can reverse mutation effects
- theyre fast growing
- cheap
