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PL1003 > Topic 2 Microbiology - Eukaryotic Micro-organisms (Mycology and Protozoa) > Flashcards

Topic 2 Microbiology - Eukaryotic Micro-organisms (Mycology and Protozoa) Flashcards

1
Q

What is mycology?

A

The study of fungi

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2
Q

What are characteristics of fungi?

A

Can be microscopic organisms

Eukaryotes

Possess a nucleus

Have several chromosomes

Diverse morphology

Fast growing and so can be used as good model organisms for studying eukaryotic genetic traits

Fungi come in many shapes and structures

Most important medically fungi are either yeasts or filamentous fungi

Some are harmful - e.g. produce contaminants

Others are beneficial - e.g. source of antibiotics

Fungi possess a cell wall made of polysaccharides - mainly Beta-glucan with mannan and chitin
Fungal cells also have a phospholipid bilayer around them

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3
Q

What are the optimal conditions for fungal growth?

A

most medically important fungi have optimal growth temperatures of around 20 - 25^0C.
Therefore they tend to exist outside the body.
However some other mammalian species have fungi in their digestive tract (e.g. cattle, sheep, horses)

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4
Q

Filamentous fungi use complex reproductive strategies which often involve spore formation. What type of reproduction is involved?

A

sexual and asexual reproduction

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5
Q

What does asexual growth allow for in fungi?

A

Allows an organism to divide rapidly under conditions which are favourable

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6
Q

What does sexual growth allow for in fungi?

A

allows for diversity in a changing ecosystem

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7
Q

What happens during asexual reproduction of fungi?

A

Asexual reproduction means there is no mixing of genetic material

  1. Mycelium (which is like a collection of fibres) produces spore-producing structures
  2. these spore-producing structures then produce spores
  3. these spores then go into the air and go into a favourable place e.g. soil
  4. these spores then germinate and become mycelium

Mother and daughter cells will be the same

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8
Q

What happens during sexual reproduction of fungi?

A

Sexual reproduction happens so there will be a mixing of genetic material from two different mycelium

  1. The two different mycelium spores get together (through plasmogamy (fusion of cytoplasm and karyogamy (fusion of nuclei)) and the genetic material inside will mix and form a zygote.
  2. The zygote goes through meiosis
  3. then the two nuclei become one and start splitting and become a spore.
  4. these spores then germinate and become mycelium

We have a + and - mycelium which get together to make diploid mycelium

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9
Q

What are some characteristics of yeast?

A

unicellular spherical fungi

typical diameter around 10 µm

Facultative anaerobes (can live aerobically or anaerobically)

sexual and asexual examples

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10
Q

What are the different strategies of asexual reproduction in yeast?

A

Binary fission and budding

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11
Q

What does binary fission result in?

A

results in two approximately equally sized daughter cells.

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12
Q

What does budding result in?

A

results in a single smaller daughter cell budding off from the parental cell.

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13
Q

Is there production of spores used by yeast?

A

no

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14
Q

Describe the appearance of filamentous fungi?

A

Typically have a hairy appearance due to the hyphal growth of filamentous structures.

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15
Q

Describe hyphae and what it results in?

A

hyphae can grow to several cm in length.
this results in an elaborative and extensive branched formation which produces a complex mass, the mycelium

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16
Q

The genetic term for fungal infections is mycosis, but what 3 groups can this be split into?

A

Superficial (cutaneous)

Subcutaneous

Systemic

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17
Q

Describe superficial (cutaneous) infections

A

Affect the surface layer of the skin, nails, or hair.

e.g. candidiasis thrush (affects tongue), tinea (ringworm)

These infections can occur at any place on the skin, but generally favour moist environments e.g. feet, groin etc

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18
Q

Describe subcutaneous infections

A

Beneath or within structures - skin, nails, hair

not life threatening

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19
Q

Describe systemic infections

A

Causes infections within the body e.g. Aspergillosis (farmers lung)

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20
Q

What are antifungal agents?

A

antifungal agents are the medicine or the chemicals that are produced to fight against fungi

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21
Q

Although fungi and mammals are both eukaryotes, what are the differences?

A

Differences in cell structure.
Fungi have a cell wall, which is lacking in mammals. In addition there are differences in terms of the composition of their membranes.

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22
Q

Where is cholesterol found?

A

in mammalian cells

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23
Q

What is ergosterol?

A

Ergosterol is a derivative if cholesterol and is found in fungi (and many protozoa) at high concentrations

It is considered essential for the survival of fungal cells.

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24
Q

What two different cellular features do fungal cells have which could be used to identify antifungals?

A

cell wall and cell membrane

25
What are some characteristics of protozoa?
unicellular organisms Found in aquatic environments but also found in our body, in animals and soil. (this does not have to be water e.g. some protozoa are found in the digestive tract of herbivores) Most protozoa are non-virulent (not infectious) In some species they may be beneficial Many herbivores have ciliated protozoa in their digestive tracts. these are not present in humans but have been described in some gorilla
26
What are the four classes of protozoa?
Amoebae Ciliates Flagellates Sporozoa
27
What types of replication are used by protozoa?
sexual and asexual replication
28
What are the different methods of cell division used by protozoa?
Binary fission, budding and schizogony
29
What is shizogony?
multiple fission - nucleus undergoes many divisions, and each is used to produce a new cell
30
What are the two different kinds of nuclei of ciliates?
a diploid sexual nucleus (macronucleus) containing all the genetic material needed by the cell Polyploid asexual nucleus (macronucleus) containing multiple copies of subsets of the genetic material However, there is a further complication as, some ciliates have more than one micronucleus present.
31
the skin provides an effective barrier to many infections. What are some examples of entry routes of infections?
Oral ingestion - G. Intestinalis (water, but can be faecal-oral) Sexual transmission - T. Vaginalis Cuts in the skin can lead to infection in the bloodstream Insect bites - T. Brucei gambiense (animal vector- tsetse fly), L. Panamensis (animal vector - sand fly) Therefore, physical attachment to human tissue is necessary for infection – directly or indirectly
32
Conditions arising from infection (protozoa) are often chronic. How long do these conditions last?
Can last several months, sometimes life-long Often complications can arise due to any further reinfections
33
What are the symptoms of the sexually transmitted protozoal infection Trichomonas vaginalis?
In females the infection is generally in the cervical area of the vagina or the urethra. symptoms include: vaginal spotting/bleeding General itching and/or sensation of burning Increased frequency of urinating Pain while urinating/during sexual activity Vaginal discharge (white, grey, yellow, or green~) which is often frothy Unpleasant 'fishy' smell Not all females show symptoms Many males show no symptoms (asymptomatic)
34
What does treatment of the protozoal infection Trichomonas vaginalis involve?
treatment often involves using metronidazole - a general inhibitor of DNA replication
35
What are symptoms of the protozoal infection Cryptosporidium parvum?
This infects the intestinal tract results in fairly severe diarrhoea for 2-7 days Dehydration, nausea and vomiting Most people recover with rehydration
36
What are the symptoms of Giardia lamblia intestinal protozoan which enters the body via contaminated food and water?
watery diarrhoea and abdominal cramps It is specific in its mode of infection as it Attaches to the duodenal wall
37
What is the protozoal infection Entamoeba histolytica and how does it infect the body?
Causes amoebic dysentery Histolytica = tissue destroyer infects the lumen of the digestive tract - generally the lumen of the bowel Leads to ulceration of the mucosal tissue of the epithelial parts of the tract.
38
What are the symptoms of Entamoeba histolytica?
Severe cramps, colitis and bloody diarrhoea
39
What can Entamoeba histolytica be treated with?
Metronidazole
40
What is toxoplasma gondii?
Blood and tissue infection which is the source of toxoplasmosis
41
What can toxoplasma gondii infect?
Can infect almost all warm-blooded animals
42
What is the definitive host of toxoplasma gondii?
Cats as they are the sites of sexual reproduction
43
Why are cats the definitive host of toxoplasma gondii?
They contain linolic acid which is not readily available in other species. Toxoplasma needs this environment for their sexual reproduction
44
How does infection arise from toxoplasma gondii?
Ingestion of undercooked meat, direct handling of cat faecal
45
Most cases of toxoplasma gondii are benign. Rare cases involve parasitic invasions. What does this do to the body?
Invades tissue of lung, heart, central nervous system, eyes etc Only after tissue invasion does this infection become a problem
46
What does tissue invasion cause when toxoplasma become a problem?
Can cause behavioural changes e.g. increased risk-taking, schizophrenia, suicide attempts, 'road rage'
47
What are acute symptoms of toxoplasma gondii?
Chills, fevers, lymphadenitis-infection of one or more lymphnodes, fatigue, blindness
48
What are the different treatments used for toxoplsma gondii?
treatments include drug therapy with: Pyrimethamine Sulfadiazine Folic acid
49
What is Leishmania and how is it transmitted?
Leishmania are a genus of intracellular parasites transmitted by female sand flie (intermediate organism) which have been infected.
50
What two forms of leishmania exist?
Cutaneous (attacks via the skin) Visceral (requires some form of ingestion)
51
What does the visceral from of leishmania result in and cause?
visceral results in invasion of reticuloendothelial phagocytes This causes enlarging of the abdominal organs
52
How is leishmania treated?
Treatment is normally with sodium stibogluconate – an antimonial compound This form of treatment can have side affects such as nausea, vomiting, diarrhoea or Joint pains
53
What is malaria caused by?
sporozoan plasmodium
54
What type of intermediate does plasmodium used?
an insect intermediate - Anopheles mosquito This is the stage involving sexual reproduction Human stage is asexual
55
when does malaria/plasmodium take place in humans?
The infection takes place after being bitten by a mosquito
56
What cells are affected by plasmodium in humans?
Both cells of the liver (hepatocytes) and the bloodstream (erythrocytes) can be affected
57
What are the symptoms of malaria?
Periodic fevers-every 48-72 hours - rupturing to release mature erthrocytic schizonts chills headaches abdominal pain nausea vomiting
58
How is malaria prevented?
Antimalarials taken prophylactically (guarding from or preventing the spread or occurrence of disease or infection) Control of Anopheles mosquito / bite prevention
59
What are the treatments for malaria and what do they involve?
Antimalarials Symptomatically Doxycycline – used to prevent malaria infection atovaquone/proguanil– used to prevent malaria infection mefloquine (prophylactic) – used to prevent malaria infection artemisinin- given after the start of an infection

PL1003 (8 decks)

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