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MIM 2 > 15. Intro to Bacteria I & II > Flashcards

15. Intro to Bacteria I & II Flashcards

1
Q

substratum

A

the surface that bacteria adhere to

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2
Q

what do bacteria need to adhere to a substratum?

A

a conditioning film: such as plasma proteins, tissue fluid

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3
Q

what are the stages of biofilm formation?

A 
adhesion
colonization
accumulation
climax community
dispersal
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4
Q

succession

A

colonies of bacteria change the environment such that different types of bacteria can begin thriving there

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5
Q

what are several diseases that have been associated with micro biome changes (dysbiosis)?

A
  • inflammatory bowel disease
  • type II diabetes
  • necrotizing enterecolitis
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6
Q

what are the physiological determinants that determine whether or not a microorganism can grow?

A
  • temperature
  • pH
  • gaseous requirements
  • minerals and trace elements
  • vitamins
  • nitrogen sources
  • carbon sources
  • energy generation
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7
Q

obligate aerobes

A

completely dependent on the presence of O2

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8
Q

obligate anaerobes

A
  • cannot grow in the presence of O2.
  • Some anaerobes are ‘aerotolerant’
  • Lack ability to deal w/ reactive O2 species
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9
Q

microaerophiles

A

Require O2 at about 0.2 atmospheres (4%). Are

inhibited, but not killed by higher O2 levels.

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10
Q

capnophiles

A

grow best in elevated CO2 (5–10%).

Streptococcus.

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11
Q

facultative anaerobes

A

grow in the presence or absence of O2. Usually
prefer growth in O2 because respiration yields 38
moles ATP/mole glucose. Fermentation yields only
2-3 moles ATP. (most bacteria fall into this group)

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12
Q

describe the bacterial growth curve in a liquid medium (such as blood)

A
  • during lag phase, bacteria adapts to environment
  • it grows as fast as it can until one component of the medium becomes limiting
  • during stationary phase, equal numbers of bacteria are growing and dying (this is when spores are produced)
  • eventually the bacteria begin to die faster
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13
Q

what is the advantage of molecular diagnosis?

A

the organism doesn’t have to be viable, faster, bc dont have to grow the bacteria. can use pcr

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14
Q

what stain would you use in a patient suspected of having TB?

A

acid-fast stain

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15
Q

what stain can you use to distinguish between different types of meningitis?

A

gram

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16
Q

Acid-fast stain

A

stains mycobacteria red and everything else blue, the surface is so hydrophobic that a gram stain won’t work

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17
Q

how do we distinguish sputum from saliva?

A

the presence of inflammatory cells

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18
Q

what are the two types of general purpose media?

A

blood agar and chocolate agar (heated to 56C to lyse the cells)

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19
Q

beta hemolysis

A

complete hemolysis, produces a clear halo around the lysed organism

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20
Q

Macconkey agar

A

differential ‘partially selective’
-used for fecal specimens, inhibits the growth of gram-positive organisms (partially selective)
-uses lactose as differential
alpha hemolysis incomplete hemolysis, the effect of hydrogen peroxide is to turn the organism green

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21
Q

Thayer-Martin agar

A

a selective medium used for the recovery of neisseria gonorrhea

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22
Q

what is the only cytoplasmic structure that bacteria contain?

A

ribosomes

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23
Q

sterol

A
  • structural lipids that maintain integrity of the membrane

- Eukaryotes have sterols, prokaryotes DONT bc they have cell wall that provides rigidity and protection.

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24
Q

what bacterial components are important in pathogen adherence?

A

pili, fimbriae, capsule

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25
Q

what bacterial components are important in avoiding complement?

A

capsule (particularly sialic acid), proteases

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26
Q

what bacterial components are important in avoiding phagocytosis?

A

capsule, leukotoxins (cytotoxins)

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27
Q

what bacterial components are important in subverting humoral immunity?

A

Fc receptors, Ig proteases, endotoxin, LPS/LTA, cell wall components

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28
Q

what bacterial components are important in subverting cellular immunity?

A

superantigens

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29
Q

bacterial capsule

A
  • external to cell wall on gram-positive and gram-negative bacteria
  • also called slime/glycocalyx
  • usually carbohydrate, but can be protein
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30
Q

what drives flagella?

A

a proton-motive force

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31
Q

the individual subunits __ of which flagella are built, serve as a __

A

flagellin

PAMPs

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32
Q

fimbriae and pili are composed of ___ subunits

A

fimbrillin

33
Q

fimbriae/pili are typically involved in __ interactions

A

lectin (a protein that binds sugar moieties)

34
Q

the scaffold of peptidoglycan consists of repeating subunits of:

A

n-acetylglucosamine and n-acetylmuramic acid

35
Q

tetra peptides branch off of __, with __ being the third amino acid

A

n-acetylmuramic acid

diaminopimetic acid

36
Q

main structural difference between gram-positive and gram-negative bacteria

A
  • Gm+ has a peptide bond cross-link bw diaminopimetic acid and the terminal D-alanine
  • Gm- just has a direct connection to the terminal D-alanine with no spacer; very few cross bridges in the gm-negative cell wall
37
Q

what piece of peptidoglycan has been used as an adjuvant?

A

muramyl dipeptide

38
Q

Why can’t mycobacterium be stained with gram staining?

A

extra mycolic acids and arabinogalactin creates an outer hydrophobic layer that prevents penetration of the dyes

39
Q

what is the gram-positive equivalent of LPS (gram-negative bacteria)?

A

teichoic and lipoteichoic acids (LTA)

40
Q

gram-negative cell structure

A
  • cytoplasmic membrane and outer membrane sandwich peptidoglycan on either side
  • the outer leaflet of the second cytoplasmic membrane is made up of half LPS and half proteins
41
Q

what is the structure of LPS?

A

Lipid A portion - toxic element
core - inner and outer
O - antigenic side chain

42
Q

periplasmic space

A
  • contains peptidoglycan
  • ‘cross-roads of the gram-negative wall’; this is where you have all the enzymes involved in importing and exporting molecules into the cell
43
Q

nucleoid

A

a long, single molecule of double stranded, helical, supercoiled DNA, the ends of which are covalently bonded together to form a circle

44
Q

do bacteria have a cytoskeleton?

A

yes, this is a relatively new finding

45
Q

what do inclusion granules in bacteria usually consist of?

A

carbon sources such as glycogen/starch, lipids etc. as well as volutin (complexed inorganic polyphosphates)

46
Q

what is the significance of extrachromosomal DNA plasmids?

A

they confer a selective advantage: antibiotic resistance, toxin production, unique substrate metabolism

47
Q

which gram-positive bacilli form spores?

A

Bacillus (aerobic) and Clostridium (anaerobic)

48
Q

which nutrient usually limits bacterial growth, leading to spore formation?

A

alanine

49
Q

describe the process of spore formation

A
  • the cell begins binary fission, but if there is nutrient shortage one of the daughter nucleoides moves to one pole of the cell
  • it produces ribosomes, replicative machinery, and a complex multilayered cell wall that allows the spore to survive in harsh conditions (heat, UV, drying etc.)
  • eventually sensors determine that it can begin growth again
50
Q
  • Aciduricity

- 2 aceduric bacteria:

A

Aciduricity = ability to tolerate low-pH

  • Lactobacilli – use proton pumps to maintain normal cytosolic pH
  • Helicobacter pylori – secretes NH3 and other bases to create locally neutral environment
51
Q

3 low-pH environments in the body

A
  • Stomach: H. pylori
  • Vagina: low-pH helps protect it from rectal bacteria
  • Pus
52
Q

Thermophiles, Mesophiles, Psychrophiles

A

Thermophiles like it hot (55-75°C)
Mesophiles like it normal (28-45°C)
Psychrophiles like it cold (15-30°C)

53
Q

Auxotroph vs. Prototroph

A

Auxotroph: requires exogenous vitamins, can’t make their own; “Auxotrophs are fastidious”
Prototroph: synthesizes its own vitamins

54
Q

Autotroph vs. Heterotroph

A

Autotroph: fixes CO2 from air to produce carbon skeletons

Heterotroph/Organotroph: takes carbon from organic material (in the lab, usually glucose)

55
Q

difference between 2 kinds of sample collection sites:

A

1) Body surfaces – have a resident microbiota (skin, mucosae, poop)
2) Sterile body sites – do NOT have a resident microbiota (blood, CSF, peritoneum)

56
Q

Liquid media is good for ____

A

monocultures

i.e., sterile site specimen → liquid media (blood cultures)

57
Q

We can measure bacterial biomass in 3 ways:

A
  • (Measuring bacterial growth = measuring bacterial biomass)
  • 3 ways: via dry weight, total protein, viable count, or turbidity.
  • Viable counting – assumes that each colony is the progeny of a single cell
  • Turbidity: measures optical density (OD) of the sample
    at a wavelength bw 500-700 nm
58
Q

Growth curve is only useful for ..

A

liquid media.

59
Q

4 phases of bacterial growth curve

ONLY for liquid media, remember!

A

1) Lag: bacteria acclimate to environment, prepare machinery for cell division. phase length depends on how different the media is from the original environment.
2) Log/exponential growth: grow until limited by physiological determinants; usually a short phase.
3) Stationary: bacterial growth rate = death rate. produces 2ndary metabolites.
4) Death/logarithmic decline

60
Q

thermophiles

A

55-75C (hot)

61
Q

mesophiles

A

28-45C (normal)

62
Q

psychrophiles

A

15-30C (cold)

a concern in blood banks

63
Q

Aciduricity refers to ____, 2 types of aciduric bacteria

A
  • low pH tolerance
  • Lactobacilli: use proton pumps to maintain normal cytoplasmic pH
  • Helicobacter pylori: secretes NH3 and other bases to create locally neutral environment.
64
Q

3 low pH environments in the body

A

stomach
vagina (helps protect it from rectal bacteria)
pus

65
Q

streptococcus is ___ , grows best in elevated CO2 (5-10%)

A

caphnophilic

66
Q

Most bacteria are _____, grow in presence/absence of O2 (usually prefer O2)

A

facultative anaerobes

67
Q

aerobic respiration yields ___ ATP/mol of glucose, while fermentation yields ____.

A

38 ATP

2-3 ATP

68
Q

sporulation is a response to ______ , two spore producing organisms.

A

nutrient limitation**

bacillus, clostrydium

69
Q

Nitrogen sources for bacteria

A
  • reduction of NO3 is most common
  • N2 fixation from air
  • in the lab hydrolysates of organic tissues
70
Q

homolactic fermenters

A

streptococci all produce lactic acid through fermentation, the only exception, all other bacteria generally prefer aerobic respiration.

71
Q

why are bacteria stabbed into the solid culture?

A

exposure to lower O2 environment promotes hemolysis

72
Q

fastidious bacteria are grown on ___ cultures

A

chocolate agar plates (contain heat lysed RBCs, more nutritious)

73
Q

Enteric bacteria are grown on ____

A

MacConkey Agar plates (partially selective and differential media), has inhibitors for commensal Gm+ (selective) and lactose producing (differential) species.

74
Q

selective media are used to grow ___, 1 ex of plate+bacteria

A
  • One specific bacteria, ex: STDs/neisseria gonorrhea.
  • These plates are treated with antibiotics/antifungals that select for only that species (so that microbiota dont take over the plate).
  • thayer-martin agar.
75
Q

corncobs are a feature of what stage in biofilm development?

A

climax community– a central filament surrounded by cocci. Signifies a nutritional interrelationship bw these organisms.

76
Q

climax communities can only form on ___

A

solid, non-shedding surfaces (tooth, prosthetics)

77
Q

feature of a fully mature biofilm

A

mushroom like extensions of bacterial clusters separated by fluid channels.

78
Q

what features of bacteria can be vaccine antigens?

A

wall and secreted proteins/lipoproteins/lipids/carbs

79
Q

what features of bacteria cause cell damage?

A

exotoxins (i.e. cytotoxins).

MIM 2 (14 decks)

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