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MMI > Lecture 4 - Bacterial Metabolism > Flashcards

Lecture 4 - Bacterial Metabolism Flashcards

1
Q

What are 3 characteristics of endotoxins? and an example

A
  1. part of a cell structure thats anchoed in the outer membrane of gram negative cells
  2. lipid molecule
  3. released from the cell when it does and disintegrates

example: lipid A in lipopolysaccharide

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2
Q

what are 4 characteristics of exotoxins? and examples

A
  1. produced by the bacterial cell’s ribosomes & is NOT part of the cell structure
  2. released from cell in many ways and causes damage to other cells
  3. is a protein
  4. has 3 types: enterotoxin, neurotoxin, and cytotoxin

examples include tetanus toxin and botulinum

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3
Q

What are the three types of exotoxins?

A
  1. enterotoxin (a toxin produced in or affecting the intestines, such as those causing food poisoning or cholera)
  2. Neurotoxin (toxin produced affecting the nerve cells)
  3. Cytotoxin (substances toxic to cells)
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4
Q

what is metabolism?

A

sum total of all chemical reactions within an organism

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5
Q

what is the difference between catabolic and anabolic reaction?

A

catabolic reactions: reactions where energy (ATP molecule) is released [breakdown of organic compounds] i.e glucose breaking down into CO2 and H2O
anabolic reaction: reactions where energy (ATP molecule) is stored i.e. formation of polysaccharides from simple sugars (glycogen from glucose)

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6
Q

6 characteristics of enzymes?

A
  1. large protein molecules (biological catalysts)
  2. make chemical reactions happen 100,000,000 X faster
  3. substrate specific (they are specific to what they work on)
  4. Have suffix “-ase”
  5. May need co-factors - e.g. metal ions like zinc, magnesium
  6. recyclable, unchanged during reaction
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7
Q

What are the 5 cellular controls that can affect the function of enzymes?

A
  1. temperature
  2. pH
  3. Saturation (how many enzymes are available to bind to their substrates; the higher the saturation, the more effective the enzyme)
  4. Salt concentrations
  5. inhibitors (i.e. mercury/ Silver)
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8
Q

What do most microbes use for energy?

A

carbohydrates like glucose

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9
Q

what are two processes by which glucose is used by microbes?

A
  1. cellular respiration (aerobic and anaerobic)
  2. fermentation

both processes use glycolysis (final product is pyruvate) to make ATP

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10
Q

What are some key features for Aerobic respiration?

A

production of more ATP (38 ATP / 1 glucose)

- faster than anarobic

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11
Q

what are obligate aerobes?

A

bacteria that need oxygen to grow

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12
Q

what are some key features for anaerobic respiration?

A
  • less ATP is produced (2-4 ATP/ 1 glucose)

- slower than aerobic resp.

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13
Q

what are obligate anaerobes?

A

bacteria that only grow without oxygen

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14
Q

What are 2 other energy sources other than glucose?

A
  1. Lipids –> broken down by lipases into fatty acids + glycerols which are used in the kreb’s cycle to produce ATP
  2. Proteins –> broken down by proteases into amino acids that end up in the kreb’s cycle to produce ATP
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15
Q

Three Factors that affect bacterial growth?

A
  1. Physical Factors (temp, ph, osmotic pressure, gas)
  2. Chemical Factors (metals, nutrients…etc..)
  3. Environmental Factors (intracellular growth)
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16
Q

Bacteria class that grows in -5 to 15 degrees Celsius?

A

Pyschrophiles

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17
Q

Bacteria class that grows in 20 to 30 degrees Celsius?

A

Psychrotrophs (i.e. Listeria)

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18
Q

Bacteria class that grows in 25 to 45 degrees Celsius?

A

Mesophiles (contain the most pathogens)

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19
Q

Bacteria class that grows in 45 to 70 degrees Celsius?

A

Thermophiles

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20
Q

Bacteria class that grows in 70 to 110 degrees Celsius?

A

Hyperthermophiles

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21
Q

Which two bacterial groups are most pathogenic to humans?

A

Psychrotophs and Mesophiles because they grow in the same temperatures as the human body

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22
Q

What is the pH for pathogens?

A

5-8 (neutrophiles)

23
Q

What happens to proteins at high or low pH?

A

they lose their function because they start misfolding

24
Q

What happens to a cell in isotonic solution?

A

cell remains stable because the particles outside the cell match the particles inside the cell

25
Q

what happens to a cell in hypotonic conditions?

A

more particles in the cell than in the solution so water moves into the cell an causes the cell to explode

26
Q

what happens to a cell in hypertonic conditions?

A

more particles in the solution and less particles in the cell so the water leaves the cell causing the cell to shrink and membranes to collapse (called plasmolysis)

27
Q

What happens to a RBC if exposed to dilute solution?

A

dilute means theres more water than solvent so water will rush into the red blood cell to balance and will create a hypotonic solution and burst [hemolysis]

28
Q

what happens to a RBC if exposed to a concentrated solution?

A

there will be more solute outside the cell so water will rush out and cell will shrink [plasmolysis]

29
Q

What are obligate halophiles?

A

bacteria that need high salt concentrations
they are NOT human pathogens

i.e. dead sea halophiles need 30% of salt for growth

30
Q

What are facultative halophiles?

A

these bacteria can tolerate 2-15% salt concentrations

includes: enterococcus species, vibrio species (enteric bacteria like cholera), and some staphylococci (usually on the skin because its salty when we sweat)

31
Q

What is a aerotolerant anaerobe?

A

bacteria that can tolerate oxygen but they cant grow in it fully; they can only grow and ferment in anarobic conditions; forms little spores

32
Q

What is a microaerophile?

A

bacteria that need oxygen to grow but just not the same concentration as the air so they grow at mid level of the test-tube

33
Q

Two anarobic tools for growing bacteria in the lab?

A
  1. anarobic jar

2. anarobic box

34
Q

Two sources of chemical factors that affect bacterial growth?

A
  1. sources of Carbon, Nitrogen, Oxygen, Sulfur, Phosphorous and trace elements
  2. sources of organic growth factors
35
Q

what are two examples of organic growth factors?

A
  1. yeast extract in artificial media

2. cysteine or other amino acids

36
Q

4 characteristics of intracellular microorganisms

A
  1. evade defense mechanisms like WBC
  2. needs antibiotics that penetrate the host cell membranes to treat the infection
  3. some cannot be grown on artificial media and must be cultured in living cells
  4. may be dependent on host cell for energy (i.e. chlamydia lacks enzymes to produce ATP so it uses host cell)
37
Q

What kind of microorganism is Listeria?

A

facultative intracelluar (need to grow inside human host cells but can also grow outside of them too like in food)

38
Q

How does bacteria reproduce?

A

Binary fission

- one bacteria produces two exactly same daughter by cells by splitting its own DNA

39
Q

What is generation time? what is it dependent on?

A

the time for one bacterium to divide into two
depends on media and growth conditions

aerobic bacteria grow faster than anaerobic bacteria because they produce more ATP

40
Q

How do we express bacterial number?

A

in logarithmic expression e.g. 1 x 10^8

41
Q

What are the 4 phases of bacterial growth?

A
  1. Lag phase –> this is when the bacteria is just starting to grow
  2. Exponential phase or “log phase” –> period of time where the bacteria grows the most
  3. Stationary phase –> plataeuing of bacterial growth because growth # = death #
  4. Death or decline phase –> when the bacteria dies off usually due to build up of its own toxic by-products
42
Q

which phase is the most important for antibiotic susceptibility?

A

exponential/log phase

43
Q

What are biofilms?

A

a thin slimy film of bacteria that adheres to a surface

44
Q

5 characteristics of biofilms

A
  1. involved in over 85% of human infection
  2. dynamic –> bacteria are not stuck and they can leave the biofilm to start another infection elsewhere
  3. slimy matrix is made up of polysaccharides, proteins, DNA and bacteria
  4. WBC cannot penetrate biofilms
  5. Antibiotics are ineffective against bacteria that live in biofilm (they must be manually removed like scraped off)
45
Q

What is agar composed of?

A

sterile complex polysaccharide from algae (solid culture) and looks like gelatin when its solidified

animal blood like sheep or horse is added to it for nutrients

46
Q

why cant human blood be used as a nutrient source in blood agar plates?

A

because antibodies inhibit the growth of bacteria

47
Q

What is hemolysis?

A

breakdown of blood cells in agar plates

48
Q

what is hemolysis in BAP tell us?

A

used for presumptive bacterial identification of streptococcus species

49
Q

what is alpha hemolysis?

A

partial breakdown of RBC (greening) under and around the colony of bacteria (not as bright)

50
Q

what is beta hemolysis?

A

total breakdown (clearning) of RBC around and under the colony (super bright)

51
Q

What is gamma hemolysis?

A

no breakdown of RBCs around or under the colony (no brightness)

52
Q

What is differential media?

A

Differential media are used to differentiate closely related organisms or groups of organisms. i.e.blood agar for streptococcus identification and grouping via hemolysis

53
Q

what is selective media?

A

Selective media allow certain types of organisms to grow, and inhibit the growth of other organisms.

54
Q

What is an example of a combined selective and differential agar medium?

A

MacConkey Plate –> inhibits growth of Gram positive bacteria (selective) and contains lactose to differentiate between lactose fermenting and non-fermenting gram negative bacteria (differential)

MMI (18 decks)

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