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BM211 microbiology > Block C > Flashcards

Block C Flashcards

1
Q

are fungi unicellular or multicellular

A

mostly multicellular, forming a network of hyphae

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2
Q

what can hyphae that extend above the surface produce

A

asexual spores called conidia

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3
Q

what are compact tufts of hyphae called

A

mycelia

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4
Q

what are most fungal cell walls made of

A

chitin

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5
Q

what do Mycorrhizae help plant roots obtain

A

phosphorus

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6
Q

what are fruiting bodies

A

macroscopic reproductive structure produced by fungi

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7
Q

what are examples of fruiting bodies

A

mushrooms and puffballs

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8
Q

what are the three forms of asexual fungi reproduction

A

growth snd spread of hyphal filaments, asexual production of spores, simple cell division

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9
Q

what can happen when fungi sexually reproduce

A

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

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10
Q

when did fungi and animals diverge

A

1.5 billion years ago

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11
Q

what are the key genera of chytridiomycetes

A

allomyces, batrachochytrium

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12
Q

what are the earliest diverging line of fungi

A

chytrids

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13
Q

what are the key genera of zygomycetes and glomeromycettes

A

rhizopus, encephalitozoon, glomus

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14
Q

what are zygomycetes primarily known for

A

food spoilage, commonly found in soil and decaying plant material. all are coenocytic and form zygospores

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15
Q

what are glomeromycetes

A

small group of fungi that have major ecological importance, reproduce asexually only, don’t grow independently

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16
Q

what are the key genera of ascomycetes

A

saccharomyces, candida, aspergillus

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17
Q

where are ascomycetes found

A

aquatic and terrestrial environments

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18
Q

saccharomyces cerevisae

A

cells are spiral to oval, cell division through budding, flourish in sugary environment, sexual reproduction through mating

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19
Q

mushrooms and basidiomycetes

A

key genera are agaricus and amanita, over 30,000 described species, undergo both negative and sexual reproduction

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20
Q

hyphal growth

A

unicellular organisms divide, exponential growth

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21
Q

how do fungi cause disease

A

inappropriate immune responses, toxins (mycotoxins), host infection (mycoses)

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22
Q

aspergillus spp

A

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

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23
Q

what is superficial mycosis

A

superficial means the fungus only infects the surface layer of skin, hair or nails, mostly treatable with topical anti fungal creams or liquid aerosols

24
Q

what are fungi that cause superficial mycoses called

A

dermatophytes

25
Q

superficial mycoses caused by trichophyton spp

A

causes fungal infections of the feet and other moist skin surfaces, transmitted by spores

26
Q

what are subcutaneous mycosis

A

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

27
Q

what is sporotrichosis

A

caused by the saprophyte sporothrix schenckii, an occupational hazard for those working in close contact with soil

28
Q

what is chromoblastomycosis caused by

A

fonsecaea pedrosoi, phiaphora verrucose, cladosporium carrionii, fonsecaea compacta

29
Q

chromoblastomycosis

A

fungal growth by both subcutaneous and cutaneous surface, form crusty wart like lesions on hand or leg

30
Q

what is systemic mycosis

A

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

31
Q

what is primary fungal disease

A

healthy individual infected

32
Q

what is secondary fungal disease

A

predisposing condition making the individual more susceptible to infections
individual with predisposing conditions, e.g. antibiotic therapy or immunosuppression (therapy and HIV-AIDS)

33
Q

what is histoplasmosis

A

caused by histoplamsa capsulatum, one of the most widespread primary fungal infections, inhaled spores germinate and grow in the lungs

34
Q

what is coccidiodomycosis c

A

caused by coccidioides immitis, in desert regions of USA, saprophyte, soil –> airborne when rains. respiratory systems –> a cause of pneumonia

35
Q

what is blastomycosis

A

caused by blastomyces dermatitdis, fungus lives in cotton wood and soil near bodies of water, slow lung infection, if untreated leads to skin lesions

36
Q

what is paracoccidiodomycosis

A

caused by Paracoccidioides brasiliensis, initially pulmonary, lesions forming on the face or other extremities, azole treatment

37
Q

what us cryptococcosis

A

caused by yeast form of Cryptococcus neoformans, can occur in virtually any organ of the body- initially pulmonary, seen in HIV/AIDs patients

38
Q

what is Candida albicans

A

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

39
Q

what is Pneomocytosis

A

Pneomocytosis pneumonia often caused by Pnemocytosis jirovecil
Opportunistic infection

40
Q

ergosterol inhibitors

A

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

41
Q

what are polyenes

A

a molecule with multiple conjugated double bonds

42
Q

what is the mechanism of action of polyenes

A

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

43
Q

three main classes of azoles

A

imidazoles, triazoles, thiazoles

44
Q

mechanism of action of azoles

A

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

45
Q

mechanism of action of echinocandins

A

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

46
Q

DNA synthesis inhibitors

A

nucleic acid analogues which inhibit enzymes required for DNA synthesis

47
Q

what are DNA synthesis inhibitor targets

A

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

48
Q

mitosis inhibitors

A

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

49
Q

antibiotics

A

Fungal Natural Products – microbial metabolites produced by fungi
Antibacterial and/or antifungal activity
Semi-synthetic – modified natural products, drug-like

50
Q

β-Lactam: Antibacterial

A

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)

51
Q

β-Lactam: penicillins

A

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

52
Q

penicillin G

A

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

53
Q

Cepalosporins

A

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

54
Q

Echinocandins: Antifungal

A

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)

55
Q

Mitosis Inhibitors: Antifungal

A

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

BM211 microbiology (5 decks)

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