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MEDI > Microbiological Concepts (W2) > Flashcards

Microbiological Concepts (W2) Flashcards

1
Q

what are the 4 characteristics of the cell wall in bacteria

A
  • rigidity and strength
  • protection
  • permeability
  • determines whether the cell is gram neg or gram pos
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2
Q

what determines whether a bacteria is gram pos or gram neg

A

gram pos: thick layer of peptidoglycan + has teichoic acid and lipoteichoic acid in this layer

gram neg: thin layer of peptidoglycan + has an outer-membrane over the top (with lipids and proteins)

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3
Q

what chemicals are used in what order in a gram stain

A
  1. Crystal Violet
  2. iodine
  3. Alcohol
  4. Carbol Fuchsin
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4
Q

what are the 4 principle shapes of bacteria

A
  1. bacillus
  2. coccus
  3. spirals
  4. vibrio (comma shaped )
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5
Q

what are the main arrangement

A
  1. single (random)
  2. cluster
  3. chains
  4. pairs
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6
Q

what is a glycocalyx and what are the 2 main types

A

the glycocalyx is the material around the cell wall (in some organisms)
1. capsule
2. slime

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7
Q

what are the characteristics of the capsule glycocalyx (4)

A
  • highly organised
  • firmly attached
  • protects against phagocytosis
  • some bacteria are typed (distinguished) by capsule composition
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8
Q

what are the characteristics (5) of the slime glycocalyx

A
  • not highly organised
  • not firmly attached
  • helps to slide on surfaces
  • protects the bacterium from drying
  • it is easily washed off
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9
Q

what do bacteria with a glycocalyx have a higher virulence (more pathogenic)

A

the glycocalyx permits;
- Adherence
– Protection from phagocytosis
– and potentially some protection from antibiotics

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10
Q

what does a capsule glycocalyx look like on a gram stain

A
  • it does not absorb stains but it is permeable so the colour will still stain the cell wall but there will be a colourless area outside the cell
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11
Q

what are the 3 outer structures (projections) on some bacteria and what are their roles

A
  • Flagella - motility
  • Fimbriae - adherence
  • Pili - adherence and conjugation
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12
Q

what structure in bacteria is bristle like, present in multiple numbers, and adheres to host tissues.

A

Fimbriae

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13
Q

what structure in bacteria is bristle like, present in pair or singularly, long projections, and adheres to other bacteria during dna transfer

A

Pili

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14
Q

what is the name of the polar distribution
with one flagella from one end

A

monotrichous

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15
Q

what is the name of the polar distribution
with multiple flagella from one end

A

lophotrichous

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16
Q

what is the name of the polar distribution
with multiple flagella from both ends

A

amphitrichous

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17
Q

what is the name of the polar distribution
with multiple flagella around the whole cell

A

peritrichous

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18
Q

What are bacterial endospores and what are they for

A

They are a copy of the bacteria’s dna made from its cytoplasm, that is enclosed in a thick protein layer, for survival.

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19
Q

why are bacterial spores harder to kill

A

they are resistant to heat and disinfectants and they can survive years in soil and dust

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20
Q

how do bacteria reproduce, and give details on the process

A
  • they reproduce asexually, by binary fission
    this is where one single cell splits into 2 identical daughter cells
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21
Q

what is generation time and what factors affect it (for bacteria)

A

generation time is the time it takes for the number of bacterial cells to double.
it is affected by environmental conditions and location
eg - it is faster in vitro (lab) and slower in vivo (humans)

22
Q

what are the 4 stages of the bacterial growth curve in broth solution

A
  1. Lag phase
  2. Exponential phase
  3. Stationary phase
  4. Death/decline phase
23
Q

what are the 5 atmospheric preferences that bacteria have and what do they each mean

A
  1. Obligate aerobe - must have O2 (grow in air)
  2. microaerophiles - must have low O2 (6-16%)
  3. Obligate anaerobes - must have no oxygen
  4. facultative anaerobes - can grow with or without O2
  5. Carboxyphiles - grows best in increased O2
24
Q

what are the 3 temperature preferences that bacteria have and what do they each mean

A

Psychrophiles - prefer cold (0-20)
Mesophiles - prefer medium (10-45)
Thermophiles - prefer hot (45-85)

25
Q

what is the optimum temperature for a psychrophile

A

15

26
Q

what is the optimum temperature for a mesophile

A

37

27
Q

what is the optimum temperature for a thermophile

A

50-55

28
Q

what are the 3 ph preferences that bacteria have and what do they each mean

A

Acidophile - prefers ph below 5.5
neutrophiles - prefer ph between 7.2 to 7.6
Alkalophiles - prefer ph between 8.5 to 11.5

29
Q

Catabolism is…

A

larger molecules into smaller molecules

30
Q

anabolism is…

A

smaller molecules into larger molecules

31
Q

what type of reactions mediate energy storage

A

redox reactions

32
Q

what are the products of respiration and fermentation

A

respiration:
- lots of atp
- H2O and CO2

fermentation:
- low atp
organic waste (eg alcohols and acids)

33
Q

what are the 3 types of Host-Microbe relationships

A

mutualism - both benefit
commensalism - symbiotic (one benefits without harming the other
parasitism - one benefits while other is harmed

34
Q

what are 4 beneficial roles of Normal flora

A
  1. compete with foreign microbes for colonisation site
  2. normal flora in large intestine produces vitamin B and K
  3. secrete chemicals that antagonise foreign microbes
  4. stimulate developing immune system in children
35
Q

what are the 5 stages of infectious disease

A
  1. incubation period
  2. prodromal phase
  3. invasive phase
  4. decline phase
  5. convalescence
36
Q

what happens during the incubation period of infectious disease

A

colonisation of microbe (overcoming host immune system)
host has no symptoms

37
Q

what happens during the prodromal phase of infectious disease

A

increase in numbers of microbe
host has mild symptoms

38
Q

what happens during the invasive phase of infectious disease

A

it becomes an identifiable disease
there is a dramatic increase in microbes
- this stage will continue to death if no intervention

39
Q

what happens during the Decline phase and convalescence of infectious disease

A

Decline phase- reduction of microbes and decline in symptoms
Convalescence- recovery

40
Q

what are endotoxins and exotoxins and what do they contribute to

A

they are toxins produced during an infection, they contribute to the virulence of a microbe as toxins can kill host cells

41
Q

what 4 things can a cell produce that will increase its virulence

A
  • toxins
  • enzymes
  • adherence factors
  • haemolysins
42
Q

what is the difference between endotoxins and exotoxins

A

Exotoxins are secreted by living bacterial cells
( Primarily gram pos bacteria)

Endotoxins are released when the organism dies and the cell wall breaks down (primarily in gram neg organisms with lipopolysaccharides)

43
Q

what are haemolysins, what are the 3 types, and how are they identified

A

they are lipids or proteins that cause lysis of red blood cells
the 3 types are
- Alpha (green/grey zone) - Partial lysis
- Beta (clear zone) - complete lysis
- Gamma - no lysis

44
Q

where are microbial biofilms found and give some examples

A
  • wet surfaces
  • eg. teeth, dental implants, contact lenses, water supplies
45
Q

what makes up microbial biofilms

A
  • microbes
  • cell debris
  • extracellular
46
Q

how does plaque lead to tooth decay

A

increase in plaque = increase in bacterial numbers = increase in acid production = increased demineralisation

47
Q

how does oral bacteria produce acid

A

by fermenting carbohydrates

48
Q

what are the 3 types of microscopes (and subtypes for 2 of them)

A
  1. Compound light microscope
    - Dark ground
    - Bright field
    - Phase contrast
  2. Fluorescent microscope
  3. Electron microscope
    - transmission
    - Scanning
49
Q

what controls light in a Compound light microscope

A
  • Condenser
  • Diaphragm (iris)
50
Q

How would you increase contrast when looking at an unstained preparation with bright field illumination?

A

closing the condenser diaphragm

51
Q

what is the difference between selective and differential media

A

selective - only allows certain bacteria to grow + inhibits others
differential - allow bacteria to be distinguished from each other

MEDI (11 decks)

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