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Microbiology > Bacteria > Flashcards

Bacteria Flashcards

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1
Q

Why should we study bacteria?

A
  • Evolutionary purposes
  • Microbiome (bacteria within the body)
  • Infections
  • Antibiotics
  • Bioremediation (using bacteria to break down waste products)
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2
Q

What are the differences between prokaryotes and eukaryotes?

A 
Prokaryote
- No membrane bound organelles 
- No nucleus 
- 70S ribosomes 
- Circular DNA 
- Cell walls = peptidoglycan 
Eukaryote
- Membrane bound organelles 
- No flagellum 
- 80S ribosomes
- Chromosomal DNA
- Cell walls = cellulose
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3
Q

What are archaea?

A

Single-celled organisms that live in the most extreme conditions

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4
Q

What are the levels of the classification system?

A 
Domain (archaea, bacteria, eukarya) 
Kingdom 
Phylum 
Class 
Order
Family 
Genus 
Species
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5
Q

What is contained in bacterial cytoplasms?

A

80% water
Molecules required for life and reproduction
DNA
Ribosomes

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6
Q

What does the cell membrane of bacteria consist of?

A

Phospholipid bilayer with selective carrier proteins = regulate the uptake of nutrients

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7
Q

What does the cell wall of bacteria contain?

A

Peptidoglycan which provides strength

Toxic molecules

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8
Q

Where in a bacterial cell is the common site for antibiotic action?

A

Cell wall

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9
Q

What is the composition of a gram negative cell wall?

A

Thin layer of peptidoglycan

Outer membrane which is external to the cell wall

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10
Q

What compounds are found on the outer membrane of gram negative cell walls?

A 
Lipopolysaccharides 
Endotoxins 
Proteins 
Lipoproteins 
- Protect bacteria from harmful substances in the environment
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11
Q

Do gram negative cell walls retain crystal violet dye?

A

No

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12
Q

Do gram negative cell walls retain counterstain?

A

Yes - they appear pink

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13
Q

What is the composition of a gram positive cell wall?

A

Thick layers of peptidoglycan

Chains of teichoic acids extend off the plasma membrane and through the cell wall

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14
Q

What are teichoic acids?

A

Sugar containing polymers

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15
Q

What is the function of teichoic acids?

A

Assist in maintaining cell shape

Help bacteria infect cells and cause disease

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16
Q

Do gram positive cell walls retain crystal violet dye?

A

Yes - retained in thick layers peptidoglycan making it appear purple

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17
Q

How might bacteria excrete extracellular materials?

A

In capsules

In slime layers

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18
Q

What are capsules and how are they attached to bacteria?

A

Polymers of simple sugars which are firmly attached to bacteria

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19
Q

What is the function of capsules?

A

To protect bacteria from ingestion and destruction by white blood cells

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20
Q

Are capsules hydrophilic or hydrophobic?

A

Hydrophilic - prevent water loss

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21
Q

What is the slime layer composed of and how is it attached to the bacteria cell?

A

Glycocalyx = carbohydrate enriched coating which provides a protective coat from the host factors
Loosely attached with bacteria so can be easily washed off

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22
Q

What can capsules and slime layers both form?

A

Biofilms

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23
Q

What are flagella?

A

Long whip like structures required for motility

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24
Q

What are the three components of flagella?

A

Long spiral filament
Hook
Motor

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25
Q

What are long spiral filaments composed of a what is their function?

A

Composed of protein flagellin which is attached to a hook

Act as a propeller

26
Q

What is the function of the hook?

A

Transmit torque = a twisting force that causes rotation

Attached to the basal body

27
Q

What is the function of motors?

A

Drive rotation

28
Q

What are pili and what are their function?

A

Hair like appendages that are short but stronger than flagella
Involved in forming biofilms and attachment of cells to each other

29
Q

What are endospores?

A

Dormant forms of bacterium which are resistant to extreme conditions

30
Q

What are the functions of endospores?

A

Ensures survival of bacteria through periods of environmental stress

31
Q

How do bacteria grow?

A

Exponentially by binary fission = asexual production

- Genetic material is duplicated and the cell divides in two

32
Q

What is generation time?

A

The time in which it takes one bacteria cell to become two

33
Q

What is bacteria growth limited by?

A

Space
Nutrient availability (carbon, nitrogen, phosphate)
Competitors
Temperatures

34
Q

What are the four phases of growth?

A

Lag
Exponential
Stationary
Death

35
Q

What occurs during the lag phase of growth?

A

Bacteria express genes
Bacteria adapts to the surrounding conditions
Chemical composition required for growth is established

36
Q

What occurs during the exponential phase of growth?

A

Bacteria grow as quickly as possible

37
Q

What occurs during the stationary phase of growth?

A

Growth = death
Population is stable
Overall growth stops due to something limiting growth

38
Q

What are the methods of measuring growth directly?

A

Counting bacterial cells

  • Microscopes
  • Flow cytometer
  • Plate counts
39
Q

What are the methods of measuring growth indirectly?

A

Estimating number based on indirect measure of growth

  • Optical density
  • Measuring respiration
40
Q

How is bacterial growth measured using a flow cytometer?

A

Counting cells that pass through a light detector

41
Q

How is bacterial growth measured using plate counts?

A

Cultivation = grow bacteria and count individual colonies

42
Q

How is bacterial growth measured by optical density?

A

The higher the number of bacteria cells the greater the turbidity (cloudiness)
Using a spectrophotometer

43
Q

How is bacterial growth determined by measuring respiration?

A

Using a dye

44
Q

What are the pros and cons of measuring bacterial growth with a microscope?

A 
Pro = relatively quick and easy 
Con = Human error and you cannot distinguish between dead and alive bacteria
45
Q

What are the pros and cons of measuring bacterial growth by cultivation?

A 
Pro = you can ensure bacteria is alive
Con = human error, time consuming, not all bacteria can be cultured, optimum conditions may be hard to replicate
46
Q

What are the pros and cons of measuring bacterial growth by optical density?

A 
Pro = relatively quick and cheap 
Con = cannot distinguish between dead and alive bacteria
47
Q

What are the pros and cons of determining bacterial growth by measuring respiration?

A 
Pro = you can ensure all bacteria are alive 
Con = just because bacteria is respiring does not mean it is growing and dividing
48
Q

How can bacteria be viewed?

A

Light field microscopy
Dark field microscopy
Fluorescence microscopy

49
Q

What are the three mediums in which bacteria can be grown?

A

In broth = liquid
In agar = solid
In sloppy agar = semi-solid

50
Q

What are the pros and cons for growing bacteria in a broth?

A 
Pro = liquid mediums are good for enriching number of bacteria
Con = unable to know exactly what is in the broth
51
Q

What are the pros for growing bacteria in agar?

A

Pro = good for bacterial identification, able to observe colonial morphology, able to assess the purity of a culture

52
Q

What are the pros for growing bacteria in sloppy agar?

A

Pro = good for demonstrating motility, good for preserving bacteria

53
Q

What features of bacteria enable them to be identified?

A 
Colour 
Shape
Size 
Smell 
Effect on the medium growth it is in
54
Q

Diseases caused by what type of bacteria are hard to diagnose?

A

Non-culturable bacteria

55
Q

Name five different shapes of bacterial cells.

A 
Coccobacillus 
Cocci
Comma shaped 
Rod 
Diplococci
56
Q

Name four different ways in which bacterial cells grow.

A

Bunch of grapes
Chains
Diplobacillus
Palisades

57
Q

Name four staining methods used to identify bacteria.

A

Simple stain
Negative stain
Fluorescent stain
Gran stain

58
Q

Describe the process of gram staining.

A
  1. Fixation
  2. Crystal violet added (retained by gram positive)
  3. Lugol’s iodine
  4. Decolourizatiom
  5. Safranin
59
Q

What biochemical tests may be used to identify bacteria?

A

Analysis of sugar fermentation products
Ability to utilise specific sugars
Analysis of enzymes
Growth under aerobic and anaerobic conditions

60
Q

What molecular techniques may be used to identify bacteria?

A

PCR
QPCR
RT-PCR
Next generation sequencing

Microbiology (18 decks)

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