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Microbiota On Mucosal > C1/2 Intro And Mycoses > Flashcards

C1/2 Intro And Mycoses Flashcards

1
Q

Give some examples of fungi

A

Yeast, mushroom, moulds

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2
Q

What does heterotrophic mean

A

External digestion
They secrete enzymes breaking down organic material to feed on

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3
Q

Explain the use of fungi in biotech for isobutanol

A

Sach cerevisiae easily manipulated and can clone bacterial genes into it in media and grow on media to isolate isobutanol used for other chemicals or fuels

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4
Q

Fungi are often saprophytes. What does this mean

A

They live on dead material

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5
Q

What 3 relationships can they have with others

A

Parasitic (eg blastocystis)
Commensal - candida Al
Symbiotic relationship eg lichens live with Cyanobacteria

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6
Q

What is yeast morphology and give 3 model organism examples

A

Oval/round shape
Single cell
Haploid or diploid if it mates with MATa for example with MATalpha

Candida , s cerevisiae or cryptococcus neoformans

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7
Q

How do they divide

A

By budding (from mother cell)

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8
Q

What morphology do most fungi take which isn’t single cell and give characteristics

A

Filamentous
Either septated or aseptate
Also haploid or diploid or dikaryote

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9
Q

What are dikaryote

A

When they’ve mated but nucleus hasn’t fused

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10
Q

Most are dimorphic eg yeast to hyphae for candida for virulence. In response to what sorts of things can they change morphology to eg pseudohyphae or hyphae

A

Temp,co2, nutrients,ph

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11
Q

Explain how in nitrogen limiting sacharomyces cerevisiae can form paeudohyphae cells

A

Low N source causes lack of daughter budding off, instead the budding cells form long chains and no longer oval

elongating at one side moving away from the site of low N source in hopes to find more sources

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12
Q

Why would this happen

A

N can’t support rapid budding anymore

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13
Q

How does ceyptococcus (usually yeast) otoh respond to LOW nh4 aswell to form filaments (2 potential reasons why)

A

In low ammonia only it will filament if they mate with opposite group ie mata and matalpha (in replete revert back to yeast cells)

Form diploid filaments

Reason 1- filaments might be moving away to find more nitrogen

Reason 2- forming spores when diploid organisms form which are stress resistant

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14
Q

Why would spores form

A

Resistant to environmental stress

Filaments will start to form aerial hyphae and also basidium where spores form

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15
Q

What other things can they Sense to allow change from yeast and how

A

Sucrose, glucose , fructose

Have transporters eg mep2 for nitrogen which sense how much is coming in from host metabolism

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16
Q

Explain the evolution of receptors in yeast

A

Some will act act both transporters and signal inducers intracellularly

Some will only bind ligand and produce signal but no transport occurs

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17
Q

What senses ammonia in yeast

A

Mep2 transporter and signalling inducer (2 diff functions)

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18
Q

What does signalling in low ammonia allow through mep2 (not present in mutants)

A

Filamentation

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19
Q

What is suggested of the mechanism that brings about this change

A

A conformational change like in gpcr

Where usually pore closed and the CTD away from it

In these conditions brings CTD closer by phosphorylation and opens pore for nh4 signalling and transport

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20
Q

How can asexual division occur (many ways)

A

Cell divides into daughter cells and formation of new cell wall around
Eg budding or fragmentation

Or

can asexually undergo spore production (conidia are asexual spores)

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21
Q

Sexual reproduction can also occur through Union of compatible nucleus/fusion of haploid hyphae. What types of spores

A

Ascospores (form in the ascus)
Basidospores (form in the basidia)
Zygospores

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22
Q

Give examples of ascomycetes phylum and basidiomycetes

A

Candida, yeast, aspergillus

Basidia = cryptococcus

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23
Q

Explain both haploid and diploid life cycles/ vision (example of yeast/ascomycetes)

A

Haploid cell can undergo haploid life cycle of budding (asexually)

Or can mate with other MAT type to
Form a diploid a/alpha zygote with fused nucleus
Which can either undergo diploid cell cycle of budding OR Can undergo meiosis

THIS MEIOSIS FORMS 4 haploid spores (2a 2alpha) combine within an ascus eg under low nutrients

Can then germinate/release and mate with others again as haploid

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24
Q

How is it different in basidiomycetes like c neoformans

A

spores will form outside of basidium after meiosis

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25
Q

Explain the sexual reproduction of cryptococcus neoformans

A

Haploid yeast with fuse of diff mat types
To form hyphal dikaryons (where nucleus hasn’t fused yet)
Basidium formation and nuclei fusion will then occur
Can undergo meiosis after nuclei fusion, allowing sporulation process and then germination releasing haploids

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26
Q

Can some ceyptoccus unisexually mate (without need of 2 cells to diff mating types and form monokaryon) - homothallic monokaryotic fruiting

A

Yes

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27
Q

What carries the genes for mating (sequence determines type)

A

The mat locus

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28
Q

How many copies of mat and mat alpha loci do you have

A

2 but one of each is silenced by chromatin

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29
Q

What happens when spores germinate to determine mat a or mat alpha / switch In homothallic mating (cells capable of self fertilisation) - this is not present in heterophallic mating where need 2 compatible mycelia

A

Germinate, undergo 1 round of replication and produce an endonuclease which can cleave mat locus allowing a gene conversion event

Eg 1 cell mat a will give rise to both mat a and mat alpha for mating
(Only in homothallic yeast eg cryptococcus are able to do this)

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30
Q

What do 2 cells mating (heterothallic outcrossing between compatible mycelia) produce sensed by the other gpcr

A

Alpha and a-factor pheromones which bind gpcr and allow protrusions to fuse the cells

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31
Q

What does binding of this to gpcr do

A

Activate signaling proteins within a ste5 scaffold needed to stop cell cycle and this allows production of protrusions called shmoo which then interact with eachother for fusion

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32
Q

What are the only 2 things separating other euk cells from fungi

A

Cell wall and polysaccharide capsule

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33
Q

Why would polysach capsule be formed by some eg c neoformans

A

In response to environmental stresses to prevent dessication

Or in the body to stop phagocytosis

34
Q

What defines the cell wall (both immunogenic and adherant properties eg b glucans)

A

Mostly Polysaccharides like chitin, b1,3 and b1,6 glucans ,Mannoproteins

With manno on the outest part , b glucans then under is chitin

Then inner :
Other gp, pigments and enzymes also for organic degradation (inner structures)

35
Q

What attaches to mannan forming gp

A

Manno proteins

36
Q

What is below cell wall

A

Cell membrane lipid bilayer

37
Q

What is the difference between mycology and mycoses

A

Mycology is study of fungi

Mycoses is the fungal disease

38
Q

Why is it suggested they are accidental human pathogens unlike plant pathogens which require host for life cycle

A

Prefer to live environmentally eg cryptocccus

They don’t need host for life cycle

39
Q

What is an example of a superficial, non life threatening fungal mycoses which affects skin or hair usually

A

Malassezia furfur which is saprophytic whcih can cause both a skin infection called pytiriasis versicolor and dandruff

Can be due to humidity, oily skin or inherited predisposition

40
Q

What are cutaneous infections called and what they grow on

A

Dermatophytoses of the keratin in skin, hair or nails

41
Q

Give examples

A

Tinea pedis (athletes foot)
Tinea barbae (beard)
Tinea unguium (nails)

42
Q

What can these skin be treated with

A

Silver given topically or imadazole anti fungal

43
Q

What needs to be treated systemically eg with itraconizole

A

Nail infection

44
Q

Where can you get them from

A

Anthropgillic eg from showers/humans
Zoophilic - from animals
Geophilic-soil

45
Q

What are subcutaneous infections usually from

A

Accidental soil agents

46
Q

What are subcutaneous infections

A

Deep infection within dermis, tissue or bone - often chronic and slow growing infection

Which can then form skin lesions or masses under skin

hard to treat and can need surgery

47
Q

Give example

A

Mycetoma eg some aspergillus

48
Q

How do systemic pathogens usually infect

A

Inhalation of spores which can germinate and if they escape macrophages eg too many spores inhaled they can cause flu like symptoms

But

eg if immunocomrpomised through cancer treatment can be a deeper issue as not cleared and disseminate throughout body

49
Q

If not cleared what can systemic form in lung like tb

A

Granulomas (aggregation of macrophages)

50
Q

Give 3 examples of true systemic pathogens accidental

A

Histoplasma capsulatum

Paracoccidioides brasiliensis

Blastomyces dermatitidis

51
Q

What do all 3 form in 25 degrees / environment vs in tissue 37c - systemic ‘true’ dimorphic pathogens

A

Hyphae in environment

Yeast in body

52
Q

Where is histoplasma found

A

Soil and avian/bat habitats

In Ohio USA for example causes endemics

53
Q

In most it is completely asymptomatic with clearance through phagocytosis when inhaled conidia. What is common in 5% of cases or alternatively immunocomrpomised

A

They form flu like symptoms like fever and coughing in 5%

Immunocompromised either chronic granulomas (yeast replication within macrophages)

or can even disseminate eg to spleen, liver and bm

54
Q

What is used to treat them

A

Azoles

55
Q

What is suggested they do to stop acidification and death within macrophages

A

Potentially block h+ ATPase

56
Q

Which 2 factors needed for colonisation of lung and survival but unsure why

A

A 1,3 glucans (potentially hide b glucans)

Calcium binding protein CBP1

57
Q

Where is paracoccidiodes brasileinses found

A

Central and South America eg Brazil

58
Q

Inhalation of conidia spores can cause what with this infection

A

Mucosal lesions eg around mouth, nose
Skin ulcerations
Pulmonary infection eg fever /flu

Rarely ever disseminate

59
Q

How is it treated

A

Amphotericin B and azoles

60
Q

Where is blastomyces found

A

Same area as histoplasma some USA states like Ohio

Soil or wood

61
Q

What is the progression of disease

A

50% are asymptomatic but some get fever like symptoms

If unresolved can lead to acute pneumonia

62
Q

How is it treated like paracocc

A

Amphotericin b and Azoles

63
Q

Which rare opportunist (need to have a dysfunctional host unlike systemic) beginning with z is associated with severe disease

A

Zygomycetes

64
Q

What are zygomycetes and give example

A

Saprophytic mould fungi (filamentous)
Eg rhizopus in decaying fruit/veg

65
Q

How can it cause necrosis of the brain - and subsequent death if untreated (rhinocerebral necrosis)

A

Can extend from nasal mucosa through nasal sinuses to the brain

66
Q

Invasion to other sites also occurs. Where and what sort of patients

A

Lung- in neutropenic/ pulmonary disorder patients

gi tract - if someone is severely malnutritioned

67
Q

What conditions associated with zyogmycetes infection - opportunistic so needs these dysfunctions

A

Lung diseases, lymphoma and leukaemia

68
Q

What is the most common air and soil derived opportunist of aspergillus spp

A

Fumigatus

69
Q

Is it dimorphic

A

No. Only forms hyphae within the lung if spores inhaled

70
Q

What does it cause particularly in those with previous lung complications eg previous tuberculosis or immunodeficiency

A

Can reside in lung to either cause no issues or coughing etc, forming a ‘aspergilloma’ - from previous cavities from tuberculosis for example

In severe cases/ when immunocompromised can become systemic spreading to other tissues which is fatal

or the aspergilloma can cause heamorrhage if gets access to major blood vessels in hyphae form

71
Q

What lung conditions is it associated with

A

Allergic aspergillosis (over hyper immune common in asthma patients to exposure of aspergillus conidia) which can lead to excacerbation of asthma

72
Q

Give 4 sero types of worldwide opportunist cryptocccus (saprophytic)

A

Serotype A and D neoformans

B and C are c. Gatti in subtropical climates like Australia

73
Q

What issues can it cause in immunockmrposed compared to primary infections asymptomatic in healthy

A

Pneumonia, dissemination to the meninges where it crosses bbb and proliferate within brain = 100% death if not treated (by neoformans)

74
Q

Explain the strain down Canadian coast/Vancouver island growing concern

A

Back in 2002 death endemic between humans / strains causing severe disease in heathy
Found years before gatti from Australian trees imported and mated with local neoformal strain which now causes disease in healthy not just immunocomrpomised

75
Q

How is candida different to asp and cryptocccus opportunists

A

Because it is a commensal in 80% of people in ugt, gi and oral cavity

76
Q

Give some examples which are rare in which candida becomes systemic

A

Meningitis and septicemia and endocarditis

77
Q

What sort of people can it commonly cause infections in

A

Elderly or newborns

78
Q

How many women will experience candidiasis in their life

A

75%

79
Q

What is common anti fungal zinc pyrithione used for

A

Malassezia furfur or globosa commonly

Eg when you have dandruff

80
Q

How was it found toxic to fungi

A

The zinc ion is replaced by cu which then is imported into the cell and can displace fe from fe-s in proteins like aconitase required for tca cycle = death

81
Q

How did they find this out

A

When studying sensitive fungi to zpt they found they acted as if they were being poisoned with cu eg downregulated ctr1 cu importer exp

Suggesting cu was being imported

Microbiota On Mucosal (22 decks)

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