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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
what bacterial components are important in avoiding complement?
capsule (particularly sialic acid), proteases
26
what bacterial components are important in avoiding phagocytosis?
capsule, leukotoxins (cytotoxins)
27
what bacterial components are important in subverting humoral immunity?
Fc receptors, Ig proteases, endotoxin, LPS/LTA, cell wall components
28
what bacterial components are important in subverting cellular immunity?
superantigens
29
bacterial capsule
- external to cell wall on gram-positive and gram-negative bacteria - also called slime/glycocalyx - usually carbohydrate, but can be protein
30
what drives flagella?
a proton-motive force
31
the individual subunits __ of which flagella are built, serve as a __
flagellin | PAMPs
32
fimbriae and pili are composed of ___ subunits
fimbrillin
33
fimbriae/pili are typically involved in __ interactions
lectin (a protein that binds sugar moieties)
34
the scaffold of peptidoglycan consists of repeating subunits of:
n-acetylglucosamine and n-acetylmuramic acid
35
tetra peptides branch off of __, with __ being the third amino acid
n-acetylmuramic acid | diaminopimetic acid
36
main structural difference between gram-positive and gram-negative bacteria
- 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
what piece of peptidoglycan has been used as an adjuvant?
muramyl dipeptide
38
Why can't mycobacterium be stained with gram staining?
extra mycolic acids and arabinogalactin creates an outer hydrophobic layer that prevents penetration of the dyes
39
what is the gram-positive equivalent of LPS (gram-negative bacteria)?
teichoic and lipoteichoic acids (LTA)
40
gram-negative cell structure
- 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
what is the structure of LPS?
Lipid A portion - toxic element core - inner and outer O - antigenic side chain
42
periplasmic space
- 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
nucleoid
a long, single molecule of double stranded, helical, supercoiled DNA, the ends of which are covalently bonded together to form a circle
44
do bacteria have a cytoskeleton?
yes, this is a relatively new finding
45
what do inclusion granules in bacteria usually consist of?
carbon sources such as glycogen/starch, lipids etc. as well as volutin (complexed inorganic polyphosphates)
46
what is the significance of extrachromosomal DNA plasmids?
they confer a selective advantage: antibiotic resistance, toxin production, unique substrate metabolism
47
which gram-positive bacilli form spores?
Bacillus (aerobic) and Clostridium (anaerobic)
48
which nutrient usually limits bacterial growth, leading to spore formation?
alanine
49
describe the process of spore formation
- 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
- Aciduricity | - 2 aceduric bacteria:
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
3 low-pH environments in the body
- Stomach: H. pylori - Vagina: low-pH helps protect it from rectal bacteria - Pus
52
Thermophiles, Mesophiles, Psychrophiles
Thermophiles like it hot (55-75°C) Mesophiles like it normal (28-45°C) Psychrophiles like it cold (15-30°C)
53
Auxotroph vs. Prototroph
Auxotroph: requires exogenous vitamins, can’t make their own; "Auxotrophs are fastidious" Prototroph: synthesizes its own vitamins
54
Autotroph vs. Heterotroph
Autotroph: fixes CO2 from air to produce carbon skeletons | Heterotroph/Organotroph: takes carbon from organic material (in the lab, usually glucose)
55
difference between 2 kinds of sample collection sites:
1) Body surfaces -- have a resident microbiota (skin, mucosae, poop) 2) Sterile body sites -- do NOT have a resident microbiota (blood, CSF, peritoneum)
56
Liquid media is good for ____
monocultures | i.e., sterile site specimen → liquid media (blood cultures)
57
We can measure bacterial biomass in 3 ways:
- (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
Growth curve is only useful for ..
liquid media.
59
4 phases of bacterial growth curve | ONLY for liquid media, remember!
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
thermophiles
55-75C (hot)
61
mesophiles
28-45C (normal)
62
psychrophiles
15-30C (cold) | a concern in blood banks
63
Aciduricity refers to ____, 2 types of aciduric bacteria
- 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
3 low pH environments in the body
stomach vagina (helps protect it from rectal bacteria) pus
65
streptococcus is ___ , grows best in elevated CO2 (5-10%)
caphnophilic
66
Most bacteria are _____, grow in presence/absence of O2 (usually prefer O2)
facultative anaerobes
67
aerobic respiration yields ___ ATP/mol of glucose, while fermentation yields ____.
38 ATP | 2-3 ATP
68
sporulation is a response to ______ , two spore producing organisms.
nutrient limitation** | bacillus, clostrydium
69
Nitrogen sources for bacteria
- reduction of NO3 is most common - N2 fixation from air - in the lab hydrolysates of organic tissues
70
homolactic fermenters
streptococci all produce lactic acid through fermentation, the only exception, all other bacteria generally prefer aerobic respiration.
71
why are bacteria stabbed into the solid culture?
exposure to lower O2 environment promotes hemolysis
72
fastidious bacteria are grown on ___ cultures
chocolate agar plates (contain heat lysed RBCs, more nutritious)
73
Enteric bacteria are grown on ____
MacConkey Agar plates (partially selective and differential media), has inhibitors for commensal Gm+ (selective) and lactose producing (differential) species.
74
selective media are used to grow ___, 1 ex of plate+bacteria
- 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
corncobs are a feature of what stage in biofilm development?
climax community-- a central filament surrounded by cocci. Signifies a nutritional interrelationship bw these organisms.
76
climax communities can only form on ___
solid, non-shedding surfaces (tooth, prosthetics)
77
feature of a fully mature biofilm
mushroom like extensions of bacterial clusters separated by fluid channels.
78
what features of bacteria can be vaccine antigens?
wall and secreted proteins/lipoproteins/lipids/carbs
79
what features of bacteria cause cell damage?
exotoxins (i.e. cytotoxins).

MIM 2 (14 decks)

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