Block C Flashcards
are fungi unicellular or multicellular
mostly multicellular, forming a network of hyphae
what can hyphae that extend above the surface produce
asexual spores called conidia
what are compact tufts of hyphae called
mycelia
what are most fungal cell walls made of
chitin
what do Mycorrhizae help plant roots obtain
phosphorus
what are fruiting bodies
macroscopic reproductive structure produced by fungi
what are examples of fruiting bodies
mushrooms and puffballs
what are the three forms of asexual fungi reproduction
growth snd spread of hyphal filaments, asexual production of spores, simple cell division
what can happen when fungi sexually reproduce
sexual spores can be produced which can originate from the fusion of two haploid cells to form a diploid cell. spores are resistant to drying, heating , freezing and chemicals
when did fungi and animals diverge
1.5 billion years ago
what are the key genera of chytridiomycetes
allomyces, batrachochytrium
what are the earliest diverging line of fungi
chytrids
what are the key genera of zygomycetes and glomeromycettes
rhizopus, encephalitozoon, glomus
what are zygomycetes primarily known for
food spoilage, commonly found in soil and decaying plant material. all are coenocytic and form zygospores
what are glomeromycetes
small group of fungi that have major ecological importance, reproduce asexually only, don’t grow independently
what are the key genera of ascomycetes
saccharomyces, candida, aspergillus
where are ascomycetes found
aquatic and terrestrial environments
saccharomyces cerevisae
cells are spiral to oval, cell division through budding, flourish in sugary environment, sexual reproduction through mating
mushrooms and basidiomycetes
key genera are agaricus and amanita, over 30,000 described species, undergo both negative and sexual reproduction
hyphal growth
unicellular organisms divide, exponential growth
how do fungi cause disease
inappropriate immune responses, toxins (mycotoxins), host infection (mycoses)
aspergillus spp
common saprophyte (leaf mould/grains) inappropriately stored dry foods. produce toxins, most commonly aflatoxin group. which are highly toxic and carcinogenic especially to birds.
in humans cause cirrhosis (liver damage) and asthma
what is superficial mycosis
superficial means the fungus only infects the surface layer of skin, hair or nails, mostly treatable with topical anti fungal creams or liquid aerosols
what are fungi that cause superficial mycoses called
dermatophytes
superficial mycoses caused by trichophyton spp
causes fungal infections of the feet and other moist skin surfaces, transmitted by spores
what are subcutaneous mycosis
subcutaneous means it infects the deeper layers of the skin, typically caused by different fungi than superficial infections, mostly treatable with topical drugs or oral administration of azole anti-fungal agents
what is sporotrichosis
caused by the saprophyte sporothrix schenckii, an occupational hazard for those working in close contact with soil
what is chromoblastomycosis caused by
fonsecaea pedrosoi, phiaphora verrucose, cladosporium carrionii, fonsecaea compacta
chromoblastomycosis
fungal growth by both subcutaneous and cutaneous surface, form crusty wart like lesions on hand or leg
what is systemic mycosis
Systemic is the most serious, fungal growth infects internal organs
Systemic fungal pathogens normally live in soil
Infection of humans due to inhaling airborne spores
Travels from lungs to other organs and skin
what is primary fungal disease
healthy individual infected
what is secondary fungal disease
predisposing condition making the individual more susceptible to infections
individual with predisposing conditions, e.g. antibiotic therapy or immunosuppression (therapy and HIV-AIDS)
what is histoplasmosis
caused by histoplamsa capsulatum, one of the most widespread primary fungal infections, inhaled spores germinate and grow in the lungs
what is coccidiodomycosis c
caused by coccidioides immitis, in desert regions of USA, saprophyte, soil –> airborne when rains. respiratory systems –> a cause of pneumonia
what is blastomycosis
caused by blastomyces dermatitdis, fungus lives in cotton wood and soil near bodies of water, slow lung infection, if untreated leads to skin lesions
what is paracoccidiodomycosis
caused by Paracoccidioides brasiliensis, initially pulmonary, lesions forming on the face or other extremities, azole treatment
what us cryptococcosis
caused by yeast form of Cryptococcus neoformans, can occur in virtually any organ of the body- initially pulmonary, seen in HIV/AIDs patients
what is Candida albicans
Dimorphic yeast often present as a minor component of human normal flora
Diseases include mild to serious infections in immunocompromised individuals
Genome highly dynamic – chromosomal rearrangements as means of generating genetic diversity
Biofilms (medical setting) – difficult to treat with antifungal agents
what is Pneomocytosis
Pneomocytosis pneumonia often caused by Pnemocytosis jirovecil
Opportunistic infection
ergosterol inhibitors
Analogue of cholesterol in fungal plasma membranes-
provides stability and shape maintenance
The two main classes of ergosterol inhibitors are
polyenes and azoles
Mode of Action: target the unique fungal plasma membrane component,
bind to ergosterol, destabilising fungal cell membranes, leading to cell death
what are polyenes
a molecule with multiple conjugated double bonds
what is the mechanism of action of polyenes
bind to sterols in the fungal cell membrane, principally ergosterol. This places the membrane in a less fluid more crystalline state, small organic molecules leak from the cell incl. monovalent ions (K+, Na+, H+, and Cl−) resulting in cell death
three main classes of azoles
imidazoles, triazoles, thiazoles
mechanism of action of azoles
inhibit the enzyme lanosterol 14 α-demethylase which converts lanosterol to ergosterol (except for abafungin)
Depletion of ergosterol in fungal membrane disrupts the structure + functions of fungal membranes/accumulation of toxic sterol intermediates, leading to inhibition of fungal growth
mechanism of action of echinocandins
inhibit the synthesis of glucan in the cell wall: via inhibition of the enzyme 1,3-β glucan synthase, this inhibition prevents fungal cell wall synthesis
Depletion of glycan polymers leads to weakened call wall and osmotic stress
DNA synthesis inhibitors
nucleic acid analogues which inhibit enzymes required for DNA synthesis
what are DNA synthesis inhibitor targets
Candida infections and Cryptococcus neoformans
used in combination with amphotericin B and/or azole antifungals such as fluconazole
relatively weak antifungal effects
fast development of resistance
mitosis inhibitors
interferes with fungal mitosis, Relatively nontoxic drug can be taken orally but passes through the bloodstream to the skin
Target: used to treat a number of types of dermatophytoses (ringworm)
includes fungal infections of the nails and skin when antifungal creams have not worked.
Source: derived from the fungus Penicillium griseofulvum
antibiotics
Fungal Natural Products – microbial metabolites produced by fungi
Antibacterial and/or antifungal activity
Semi-synthetic – modified natural products, drug-like
β-Lactam: Antibacterial
Source: natural + semi-synthetic
penicillins: fungus -> Pencillium chrysogenum
cephalosporins: fungus -> Cephalosporium sp.
Mode of Action: inhibitors of bacterial cell-wall synthesis
irreversible binding to PBPs to prevent transpeptidation (cross linking of peptidoglycan)
β-Lactam: penicillins
β-lactam and thaizolidine rings
1st antibacterial compound (Fleming)
Penicillin resistant to beta-lactamase – methicillin flucloxacillin – used to treat staphylococcal infections, but MRSA is not sensitive to it
penicillin G
Targets: most Gram-positive bacteria and some Gram-negative cocci
staphylococcal and pneumococcal infections
Mode of Action: inactivates the penicillin binding proteins (PBPs) located within the bacterial cell wall, Interferes with cross linking of peptidoglycan -> weakening -> cell lysis
Cepalosporins
Produced by the fungus Acremonium
Cefoxitin acts by interfering with cell wall synthesis
Its activity spectrum includes a broad range of Gram-negative and Gram-positive bacteria, including anaerobes
Echinocandins: Antifungal
Mode of Action: inhibit the synthesis of glucan in the cell wall via inhibition of the enzyme 1,3-β glucan synthase
This inhibition prevents fungal cell wall synthesis
Source: semi-synthetic from pnedmocandin Bo (natural cyclic lipopeptide)
Mitosis Inhibitors: Antifungal
Mode of Action: interfering with fungal mitosis (disruption of microtubule aggregation)
tubulin inhibiting agent
Target: used to treat a number of types of dermatophytoses (ringworm)
includes fungal infections of the nails and skin when antifungal creams have not worked.
Source: derived from the fungus Penicillium griseofulvum
