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Microbiology for Dentists > 4. Bacterial Growth > Flashcards

4. Bacterial Growth Flashcards

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1
Q

How do bacteria grow?

A
  • produce and consume energy
  • anabolic/catabolic processes
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2
Q

2 types of nutrients needed for bacteria to grow

A
  • macro
  • micro
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3
Q

Define ‘macronutrients’ with examples

A
  • nutrients needed in large quantities
  • carbon, nitrogen, oxygen
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4
Q

Bacterial growth needs vary but … is always pivotal

A
  • hydrogen
  • oxygen
  • carbon
  • nitrogen
  • phosphorus
  • selenium
  • sulphur
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5
Q

Bacteria need … to … to grow

A

70-80%

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6
Q

Nitrogen is needed to create nitrogen precursors to …

A
  • nucleotides hence nucleic acids
  • amino acids hence proteins
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7
Q

Carbon sources form carbon precursors to form …

A
  • nucleotides hence nucleic acids
  • lipids and polysaccharides
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8
Q

Electron acceptors are needed for what?

A
  • with carbon sources form energy (ATP,GTP)
  • helps form nucleotides hence nucleic acids, amino acids hence proteins, lipids and polysaccharides
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9
Q

Difference between auto and auxo trophs

A
  • auxo can’t synthesise essential organic compounds e.g amino acids and nucleotides
  • auto can
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10
Q

Heterotrophs obtain C from …

A

organic chemicals

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11
Q

Heterotroph growth requirements can be … or …

A
  • simple
  • complex
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12
Q

When would bacteria be described as fastidious?

A

when organisms require large number of growth factors or are supplied with specific ones

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13
Q

Fermentation and respiration - aerobic or anaerobic?

A

ferm is anaerobic
- resp is both

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14
Q

Difference between fermentation and respiration

A
  • ferm has an organic compound used as both an electron donor and acceptor
  • resp has an electron donor oxidised with oxygen or an oxygen substitute
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15
Q

Fermentation and respiration occur in both humans and bacteria but bacteria are more …

A
  • versatile
  • wider variety of substrates and produce many different end products
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16
Q

Bacteria can be categorised by their … response in …

A
  • growth
  • presence or absence of oxygen
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17
Q

Define ‘facultative anaerobes’

A

bacteria which can survive with no oxygen

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18
Q

Define ‘aerotolerant anaerobes’

A

anaerobes that can tolerate oxygen

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19
Q

What kind of bacteria require oxygen?

A

aerobes

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20
Q

What kind of bacteria can survive with no oxygen?

A

facultative anaerobes

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21
Q

What kind of bacteria are anaerobes that can tolerate oxygen?

A

aerotolerant anaerobes

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22
Q

What kind of bacteria require oxygen at very low concentrations?

A

microaerophiles

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23
Q

Microbes in a lab are grown in what medium?

A

either solid or liquid

24
Q

What must a medium for growth have?

A

all the nutrients for the bacteria to grow

25
Q

Types of growth media

A
  • defined
  • undefined
  • complex
  • selective
  • differential
26
Q

Explain a blood agar plate

A
  • drop of blood added to agar
  • provides wide variety of nutrients
27
Q

Growth on a solid medium is seen as …

A

individual

28
Q

Define ‘bacterial growth’

A

irreversible increase in biomass and usually numbers of bacteria

29
Q

How to represent bacterial growth?

A

growth curves

30
Q

How do bacteria divide?

A

binary fission

31
Q

Why do we need to understand binary fission?

A

to understand how bacteria grow in situations where we need to control them

32
Q

Variables in binary fission

A
  • time
  • nutrients
  • genetic factors
  • temp
33
Q

In a lab, how quickly does E.Coli replicate?

A

every 20 mins

34
Q

3 phases of binary fission

A
  • cell growth
  • DNA replication
  • binary fission
35
Q

What happens in cell growth of binary fission?

A
  • cell increases in size and mass
  • production of phospholipids and cell wall
36
Q

What happens in DNA replication of binary fission?

A
  • single chromosome replicates before division
  • seperates towards end of cell
37
Q

What happens in binary fission stage of binary fission?

A
  • actual division of cells
  • inward synthesis of peptidoglycan to form septum
  • splits cell in half
  • coordinated by cytoskeletal proteins into fission ring (acts as contractile band to pinch in on itself)
  • pinches in on itself to form daughter cells
  • septum dissolves away to form seperate daughter cells and cycle repeats
38
Q

What kind of increase is seen as bacterial growth?

A

exponential

39
Q

Explain exponential growth of bacteria

A
  • slow growth rate initially
  • then speeds up rapidly
  • if conditions are optimal, large population in short time
40
Q

Things which can impact bacterial growth

A
  • instrument/self contamination
  • pathogens
41
Q

Microorganisms growing in … do not grow exponentially all the time

A

in flasks or test tubes

42
Q

Stages of batch culture

A
  • lag phase
  • log (exponential) phase
  • stationary phase
  • decline phase
43
Q

When are cells viable in batch culture?

A
  • log phase
  • stationary phase
  • some in decline phase
  • some remain at the end
44
Q

Explain lag phase in batch culture

A
  • organism adapting to new env
  • enzymes synthesised, cells increase in size
  • dont yet divide
45
Q

What determines slope and length of log phase?

A

how well the medium meets requirements

46
Q

Explain stationary phase

A
  • no net increase in cell number
  • nutrient/oxygen exhausted
  • env changed e.g pH
  • toxic products accumulate
47
Q

Explain death phase

A
  • cells die
  • often exponential
  • no energy, pH damage, toxic products
48
Q

3 methods of measuring bacterial growth

A
  • microscopic counts
  • viable counts
  • turbidimetric methods
49
Q

Explain how microscopic counts measures bacterial growth

A
  • sample added to slip (not overflowing)
  • 0.02mm space between coverslip and slide
  • whole grid has 25 squares, total area of 1mm2, volume 0.02mm3
  • observe cells in large square (or do individual squares and average)
  • amount of cells in one average x total squares
50
Q

Explain how viable counts measures bacterial growth

A
  • sample pipetted onto agar plate
  • spread evenly using sterile glass spreader
  • incubated
  • results seen (spread plate method)
    OR
  • sample pipetted onto sterile plate
  • sterile medium then added and mixed with inoculum
  • incubated
  • results seen (pour plate method)
51
Q

How many cells were in a sample when 34 colonies grew from a 0.1ml of 10-4 dilution?

A
  • 340 grown in 1x10-4
  • 10-4 is 1/10000
  • conc by factor is 10000
  • colony forming units in 1ml is 340 x10 to the 4
  • 3.4 x10 to the 6 cfu/ml
52
Q

2 units of measuring bacteria in culture

A
  • colony forming units/ml
  • cells per ml
53
Q

When do you use cfu/ml and cells/ml?

A
  • cfu for counting viable cells
  • cells per ml when coutning cells directly
54
Q

How to measure turbidimetric methods?

A
  • light through filter/prism on sample containing cells
  • unscattered light onto photocell and recorded
  • on spectrophotometer (optical density) or Klett photometer (Klett units)
55
Q

If glucose is a substrate, what is the first step of fermentation and respiration?

A

glycolysis

Microbiology for Dentists (37 decks)

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