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IIH > Bacterial Growth, Nutrition and Identification > Flashcards

Bacterial Growth, Nutrition and Identification Flashcards

1
Q

List 10 criteria for bacterial classification.

A

1 - Gram stain.

2 - The proportion of the genome formed of guanine + cytosine.

3 - Growth temperature.

4 - Ability to form heat stable spores.

5 - Electron acceptors for respiration.

6 - Photosynthetic ability.

7 - Motility.

8 - Morphology.

9 - Ability to use various carbon and nitrogen sources.

10 - Special nutritional requirements.

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2
Q

List the taxonomic hierarchy for the three-domain system.

A

1 - Domain.

2 - Kingdom.

3 - Division.

4 - Class.

5 - Order.

6 - Family.

7 - Genus.

8 - Species.

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3
Q

List 7 methods of identification of bacteria.

A

1 - Antibiotic susceptibility.

2 - Whole genome sequencing.

3 - Microscopic morphology.

4 - Antigenic properties.

5 - Cultural characteristics.

6 - Biochemical reactions.

7 - Typing.

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4
Q

List the steps involved in gram staining.

A

1 - Application of crystal violet.

2 - Application of iodine (mordant).

3 - Alcohol wash (decolourisation).

4 - Application of safranin (counterstain).

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5
Q

What is the function of a mordant?

A

To fix the dye to the bacteria.

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6
Q

How do gram positive and negative bacteria stain?

A
  • Gram positive stain purple (retain the dye).

- Gram negative stain pink (lose the dye upon decolourisation).

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7
Q

What does the term ‘coccus’ tell you about the morphology of a bacterium?

A

Indicates a round shape / clusters.

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8
Q

What does the term ‘bacillus’ tell you about the morphology of a bacterium?

A

Indicates a rod-like shape.

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9
Q

List 3 properties of Staphylococcus aureus.

A

1 - Gram positive.

2 - Coccus.

3 - Aerobic.

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10
Q

List 3 properties of the Clostridium species.

A

1 - Gram positive.

2 - Bacillus.

3 - Anaerobic.

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11
Q

List 3 properties of B. fragilis.

A

1 - Gram negative.

2 - Bacillus.

3 - Anaerobic.

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12
Q

List 3 properties of the shigella family of bacteria.

A

1 - Gram negative.

2 - Bacillus.

3 - Aerobic.

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13
Q

List 3 properties of Streptococcus pneumoniae.

A

1 - Gram positive.

2 - Coccus.

3 - Anaerobic.

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14
Q

List 3 properties of Neisseria gonorrhoeae.

A

1 - Gram negative.

2 - Diplococcus.

3 - Aerobic.

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15
Q

What are higher bacteria?

A

Bacteria with a relatively complex organisation.

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16
Q

List 2 examples of higher bacteria and the disease caused by each.

A

1 - Mycobacterium tuberculosis (causes TB).

2 - Mycobacterium leprae (causes leprosy).

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17
Q

Define acid-fast bacteria.

What makes bacteria acid-fast?

A
  • Bacteria that are resistant to decolourisation by an acid.

- These bacteria have complex cell walls that contain large amounts of lipid substances known as mycolic acids.

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18
Q

Give an example of a genus of bacteria that is acid-fast.

A

Mycobacterium.

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19
Q

What does the term ‘spirochete’ tell you about the morphology of a bacterium?

A

Indicates a flexible, spirally twisted shape.

20
Q

List 3 properties of Treponema pallidum (syphilis).

A

1 - Gram negative.

2 - Spirochete.

3 - Aerobic.

21
Q

Why are Mycoplasma pneumoniae resistant to penicillins?

A

Because they lack peptidoglycan.

22
Q

Why is the Chlamydiae phylum of bacteria known as obligate intracellular parasites?

A

Because they require host ATP (hence obligate intracellular).

23
Q

Define bacterial growth.

A

The orderly increase in the sum components of an organism (not an increase in cellular size!).

24
Q

List the phases of growth for bacteria.

A

1 - Lag.

2 - Log.

3 - Stationary.

4 - Death.

25
Q

Define dry cell weight.

A

The weight left when a cell’s water content has been removed by heating.

26
Q

What is most bacterial dry weight comprised of?

A

Organic matter comprised of macromolecules linked by anhydride bonds.

27
Q

List 2 sources of energy for medically relevant bacteria.

A

1 - Fermentation, e.g. of sugars.

2 - Respiration.

28
Q

List 2 sources of carbon for bacteria.

A

1 - CO2.

2 - Organic carbon, e.g. glucose.

29
Q

What is the primary source of nitrogen for bacteria?

A

Ammonia (e.g. in soil).

30
Q

List 2 sources of sulphur for bacteria.

A

1 - Dissolved sulphate.

2 - Found in cysteinyl and methionyl side chains of proteins.

31
Q

Give an example of a use of sulphur in bacteria.

A

Used to form co-enzymes.

32
Q

List 4 uses of phosphorus.

A

1 - Required for ATP production.

2 - Required for nucleic acid production.

3 - Required to phosphorylate proteins.

4 - Required for coenzymes such as NADP.

33
Q

What is the primary use of minerals (such as Mg2+, Ca2+ and Fe2+) in bacteria?

A

Enzyme function.

34
Q

Define siderophore.

A

A molecule present in microorganisms that facilitates iron uptake.

35
Q

At which pH do most microorganisms grow best?

A

6-8.

36
Q

At which temperature do most pathogenic bacteria grow best?

A

30-37 degrees celsius.

37
Q

Define facultative anaerobe.

A

Bacteria that can grow in both the presence or absence of oxygen.

38
Q

Why do most microbes express superoxide dismutase and catalase?

A
  • To manage oxygen toxicity:
  • Catalase converts hydrogen peroxide (H2O2) into water and oxygen.
  • Superoxide dismutase converts superoxide (O2-) into H2O2, which must be broken down by catalase.
39
Q

What type of molecule is agar?

Why is it used as a medium for bacterial growth?

A
  • A polysaccharide.

- It is used as a medium for bacterial growth as it is resistant to antibiotic action.

40
Q

Define differential media.

A

Media that distinguish bacterial species from each other.

41
Q

Give an example of a differential media.

A

Blood agar (indicates which bacteria are haemolytic).

42
Q

Define selective media.

A

Media that suppress the growth of unwanted bacteria that may be in the same sample.

43
Q

List 2 examples of media that are both selective and differential.

Explain how they work as selective and differential media.

A

1 - Mannitol salts agar (selective for gram positive bacteria, and bacteria that ferment mannitol show as yellow).

2 - MacConkey agar (selective for gram negative bacteria, and bacteria that ferment lactose show as pink).

44
Q

How does alpha haemolysis appear differently on a blood agar culture to beta haemolysis?

A
  • Alpha-hemolysin partially breaks down the red blood cells, leaving a greenish color behind.
  • Beta-hemolysin breaks down the red blood cells and hemoglobin completely, leaving a clear zone around the bacterial growth.
45
Q

List 2 examples of antimicrobial agents that are used against specific bacterial species.

For each agent, include the name of the bacterial species for which it is used.

A

1 - Optochin and Streptococcus pneumoniae.

2 - Bacitracin and Streptococcus pyogenes.

  • These agents are not used for therapy.
46
Q

Define typing.

A

The identification of certain strains of bacteria within a species that possess particular pathogenic properties.

IIH (26 decks)

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