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Sem 2: Microbiology > Week 4 > Flashcards

Week 4 Flashcards

1
Q

What is the overview of Amanita phalloides?

A

Death cap – very toxic can kill adult human
Attaches to oak (and beech) aiding nutrient absorption

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2
Q

What is the overview of Phallus impudicus?

A

Stinkhorn
Smell of faeces, which attracts insects

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3
Q

What are the two main groups of prokaryotes?

A

Bacteria – unicellular microorganisms which have cell walls but lack organelles and an organized nucleus.
Archaea - microorganisms which are similar to bacteria in size and simplicity of structure but different in molecular organization

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4
Q

What are the overview of fungi?

A

Non-motile, cell wall-bound, spore-bearing eukaryotes with a saprophytic or parasitic mode of heterotrophic nutrition

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5
Q

What are the overview of protists?

A

Eukaryotes that are not plants animals or fungi. Microorganisms and their immediate descendants, protozoa, slime molds, water molds

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6
Q

What are the similarities and differences between fungi and other eukaryotes?

A

Fungal mitochondria are elongated. All of the organelles associated with other (non-photsynthetic) eukaryotes are present

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7
Q

What is a unique biochemical process in fungi?

A

Unique method for lysine synthesis (AAA pathway, aminoadipic acid pathway)

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8
Q

What are some key enzymes in the fungal aminoadipic acid pathway?

A

Homocitrate synthase EC 4.1.3.21
Aminoadipate reductase EC 1.2.1.31
Homoisocitrate dehydrogenase EC 1.1.1.87
Aminoadipate aminotransferase EC 2.6.1.39

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9
Q

What is a unique physical trait of fungal?

A

Ridged cell wall composed of ß-1,3 and ß-1,6 linked glucans, mannan and chitin

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10
Q

What is key feature of fungi used to differentiate them from other eukaryotes?

A

Fungal cell membranes contain the sterol ergosterol (animals have cholesterol and plants have sitosterol)

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11
Q

What are the applications in medicine of fungi having ergosterol?

A

Fungal infections are hard to treat, and treatments tend to target unique aspects of fungi, including ergosterol biosynthesis

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12
Q

What is the function of ergosterol?

A

Ergosterol similar functions that cholesterol serves in animal cells, including modulating membrane fluidity

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13
Q

What are the 5 major fungal phyla?

A

Chytridiomycota
Zygomycota
Glomeromycota
Ascomycota
Basidiomycota

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14
Q

What is an overview of Chytridiomycota?

A

Water fungi. Mostly saprotrophs, some pathogens
Important constituents of of the rumen, where they digest cellulose

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15
Q

What is an example of a Chytridiomycota?

A

Batrachochytrium dendrobatidis, which causes chytridiomycosis (which is linked to dramatic declines in amphibian species) is an important research subject

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16
Q

What is an overview of Zygomycota?

A

Pin-head fungi

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17
Q

What is an overview of Glomeromycota?

A

New phylum
Mycorrhizal fungi - Important symbiotic relationships with plants

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18
Q

What is an overview of Ascomycota?

A

Industrially important fungi fall into this group, e.g. Penicillium (produces penicillin), Aspergillus (important producer of chemicals), Saccharomyces cerevisiae (brewers yeast) Some macroscopic (e.g. morels), but most are moulds

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19
Q

What is an overview of Basidiomycota?

A

Most mushrooms and other macroscopic fungi are in this group

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20
Q

What is an overview of fungal forms?

A

Most fungi are filamentous, made of tubular, thread-like hyphae
A mass of hyphae is termed a mycelium.
Sometimes large macroscopic bodies are produced
Some fungi are unicellular yeasts

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21
Q

Where does the word hyphae come from?

A

Greek meaning web

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22
Q

Where does growth occur on a fungus?

A

Growth occurs at the top of the hyphae

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23
Q

What is an overview on the structure of the hyphae?

A

Made of a thin transparent tubular cell filled or lined with protoplasm. The diameter ranges from 1 um to 30 µm.
Hyphae are colourless (hyaline), but fungal colonies are coloured due to the pigmentation in spores.
Hyphae are tapered at the tip and this region is called the extension zone.

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24
Q

What is an overview of fairy bonnet reproduction?

A

Long thin stipes (stalks) with caps on top (fruiting bodies).
These are reproductive structures (sexual or asexual).
Most of the biomass of the fungus is still in the soil
Reproductive structures are produced when the condtions are right – moist, not too hot (often in the Autumn)

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25
Q

What is the stipes and cap made from?

A

They are made from an organization of hyphae

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26
Q

What is an overview of fungal cell walls?

A

Determine the shape of the fungus.
Act as an interface between the fungus and its environment.
Protect against osmotic lysis and regulates the passage of large molecules.
Antigenic properties that can mediate the interaction with other organisms

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27
Q

What is the composition of fungal cell walls?

A

Wall is 80-90% polysaccharides.
The chytridiomycota, ascomycota and basidiomycota have chitin. The zygomycota have a mixture of chitin and chitosan

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28
Q

What is an overview of chitin?

A

Chitin is a polymer of N-acetylaglucosamine. Also found in insect exoskeletons

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29
Q

What is an overview of chitosan?

A

Chitosan is a polymer of D-glucosamine (the deactylated form of N-acetylaglucosamine)

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30
Q

What are the layers of a fungal cell wall?

A

Bottom:
Plasma membrane
Chitin + protein
Protein
Glycoprotein + protein*
Amorphous glucans*
Top

31
Q

What is the cell wall like at fungal tips?

A

Wall is much thinner at the tip
Lacks Glycoprotein + protein layer and Amorphous glucans layer

32
Q

What is an overview of the types of septa?

A

Simple septim and dolipore septum

33
Q

What are simple septum?

A

Simple septum has a large central pore (Ascomycota).

34
Q

What is an overview of dolipore septa?

A

Dolipore septum (Basidiomycota), has a narrow central pore flanked by bracket-shaped membranes, parenthosomes (clamp connections).This type of septum does not allow for the passage of nuclei, and ensures their dikaryotic condition

35
Q

Where are the septa found?

A

In most species of fungi the hyphae are interrupted by cross-wall called septa

36
Q

What are woronin bodies?

A

Structures called woronin bodies occur just behind each septum.
They are proteinaceous lattices surrounded by a membrane

37
Q

What are the function of woronin bodies?

A

They plug the septal pores if the hyphae are damaged, becoming old or undergoing differentiation.

38
Q

What is differentiation?

A

Differentiation is the regulated change of an organism from one state to another

39
Q

What are the outcomes of differentiation in fungi?

A

Dimorphism
The development of structures involved in asexual and sexual reproduction

40
Q

What is an example of dimorphism in fungi?

A

Not all fungi are filamentous, some species exhibit dimorphism (can change between a yeast and a mycelial form)

41
Q

What is an example of how fungal structure can change depending in environment?

A

Dimorphism is common among animal and human pathogens, they are filamentous outside the host, but assume a single cell form inside the host.
The change from filamentous to yeast form can be bought about by changing the environmental conditions (e.g. altering oxygen, sugar or calcium concentrations).

42
Q

What is an example of a fungus exhibiting dimorphism?

A

Candida albicans grows as a yeast in the moist mucosal membranes of humans but converts to a hyphal form to invade tissues.

43
Q

What is an advantage of fungi being dimorphic?

A

Superficial infections are filamentous and become yeast form and circulate within the host, but may become filamentous again in the host, e.g. in the heart or at the interface with the brain, and penetrate the organs

44
Q

What is apical growth?

A

The fungal hyphae extend continuously at their extreme tips.
Growth supported by the continuous movement of materials into the tip from the older regions of hyphae.
Hyphae are a continuous movement of protoplasm, which thrusts the growing tip forward
Accounts for much of their environmental and economic impacs

45
Q

What are the external outcomes of apical growth?

A

Tip growth exerts external pressure so that fungi and push through surrounding material. Important in pathogens as a way of penetrating the host
Tip growth is characteristic of fungi and essential to their roles as degrades of organic matter in the soil and as plant pathogens

46
Q

What is contained within the growing tip of the hyphae?

A

The growing tip of the hyphae contains very few organelles, instead it contains a body called the spitzenkörper (apical body).

47
Q

What does the spitenköper consist of?

A

The spitzenkorper consists of a cluster of small, membrane bound vesicles embedded in a meshwork of actin microfilaments. They are made in the Golgi body and transported to the tip.

48
Q

Where is the spitenköper present?

A

It’s always present in growing tips, disappears when growth stops and reappears if growth restarts

49
Q

What is the mechanism for hyphae growth?

A

The vesicles contain enzymes that breakdown the cell wall and deliver new wall material that is added to the growing wall
The fusing vesicle lipid grows the membrane

50
Q

How do fungi acquire nutrients?

A

Fungi have no mouth or digestive system.
Small organic food molecules may be transported directly across the plasma membrane

51
Q

How to fungi break organic materials down for food?

A

Polymeric food molecules must first be depolymerised.
Depolymerising enzymes are secreted by vesicles fusing with the membrane

52
Q

What is an overview of asexual reproduction?

A

Asexual reproduction-allows for the dispersal of many genetically identical progeny

53
Q

What is an overview of sexual reproduction?

A

Sexual reproduction allows for diversity and the ability to adapt to new environments.

54
Q

What is key in both asexual and sexual reproduction in fungi?

A

For fungi the essential item for both these processes are spores

55
Q

What is a generalised overview of asexual reproduction in fungi?

A

Spore producing structures produce spores. These spores germinate and produce structures that can produce spores

56
Q

What is a generalised overview of sexual reproduction in fungi?

A

Spore producing structures
Spores
Germination
Mycelium
Plasmogamy – fusion of cytoplasm
Dikaryotic stage – n+n
Karyogamy – fusion of nuclei
Diploid stage – 2n
Meiosis
Spore producing structures

57
Q

How do fungi sexually reproduce?

A

Complex eukaryotes have different sexes and have sex chromosomes.
Fungi have different mating types.
Mating type is determined by the mating-type locus

58
Q

What does sexual dimorphism look like in fungi?

A

Different mating types of fungi look the same, unlike the different sexes of more complex organisms

59
Q

What is the function of spore dispersal?

A

To extend beyond the existing environment.
To escape nutrient depletion.
To exploit new potential environmental niches.

60
Q

What is an overview of spores?

A

Fungi usually disperse through spores which can be produced either asexually or sexually.
Spores are all microscopic but very diverse in their size, shape, structure and colour.
These traits are often linked to the dispersal strategy

61
Q

What are agents of spore dispersal?

A

Wind or air currents - majority of species
Water - aquatic fungi
Animals - vertebrates and invertebrates
Host plants - particularly seeds

62
Q

What is an overview of spore release?

A

Before dispersal all fungal spores must be released this is either active or passive

63
Q

What is a key feature of aquatic spore dispersal?

A

Aquatic fungi (water fungi) often have flagella and are motile, exhibiting positive chemotaxis towards nutrient.

64
Q

What is a key feature of fungi spore dispersal through seeds?

A

Orchid seeds carry symbiotic fungi

65
Q

What is the overview of air dispersal?

A

Propelled far enough to fly beyond the boundary layer of air surrounding the fruiting body.
Remain suspended in air currents to be distributed appropriately.
Precipitate at the right time.

66
Q

What is the relationship between spore dispersal by air and drag?

A

For small spores, take-off is limited by drag, so seeds have to be high launch speeds to reach the air currents (drag increases with surface to volume ratio).
Minimizing drag is a primary driving force for spore shape. Drag should limit spore size to 1.8-30µm.
But forcibly ejected spores can have a size which exceeds this, suggesting that there are other evolutionary pressures

67
Q

Where are spores liberated in active liberation?

A

Spores are released from the hymenium (spore producing surface).

68
Q

What is an example of the liberation of spores in fungi?

A

Pilobolus ‘The fastest living thing on the planet’. 0-20 mph in two millionths of a second. 20,000gs

69
Q

How can passive spore liberation be achieved?

A

Wind
Rain
Animals

70
Q

What is an example of passive spore liberation through rain?

A

Puffballs such as Lycoperdon (stump puffball)

71
Q

How do puffballs liberate spores through lycoperdon?

A

Spores are produced in a sack like peridium.
When mature the peridium ruptures at the apex and water droplets depress the peridium, shooting a puff of spores into the air

72
Q

What is an example and mechanism for dispersal via an animal?

A

The stinkhorn, smells of rotting flesh, but also contains lots of sugars which attracts flies. The spores pass through the gut of the insect unharmed and are dispersed through defecation

73
Q

What are examples of fluorescent fungi?

A

Some fungi are naturally fluorescent.
It is thought that this luminescence attracts insects that then aid in spore dispersal

74
Q

What are examples of fungi being fluorescent?

A

Panellus stipticus (bitter oyster)
Omphalotus nidiformis

Sem 2: Microbiology (12 decks)

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