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microbio > week 10 > Flashcards

week 10 Flashcards

1
Q

what is a biofilm

A

community of microbial cells that are attached to a surface by an extracellular polymeric matrix (EPM)

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2
Q

true or false: about 95% microorganisms live in biofilms as long as there is at least a minimal amount of water and nutrients

A

true

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3
Q

the architecture of a biofilm supports the transport of…….

A

nutrients

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4
Q

biofilms:
provide habitat………
facilitate resource…..
promote community……..
protect cells from……..

A

diversity
capture
interconnectivity
environmental hazards

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5
Q

why are cells in biofilm 100-1000x more resistant to antibiotics

A

-physical barrier
-charged matrix
-horizontal gene transfer
- degradation of antibiotics
-persister cells
- diversity

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6
Q

what kinds of surfaces can biofilms form on

A

living tissues, indwelling medical devices, natural/ industrial systems, etc.

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7
Q

the NIH estimates that what percent of infections are caused by microorganisms growing in a biofilm?

A

80%

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8
Q

bacteria growing in biofilms help remove…….from wastewater

A

dissolved organics (unwanted)

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9
Q

how does growing attached to a surface improve fitness

A

close to other bacteria/ communities to communicate/ share resources

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10
Q

why can biofilms cause industrial systems to fail?

A

can cause localized corrosion in fuel storage tanks

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11
Q

quorum sensing identifies…….

A

population density

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12
Q

sequence of formation of biofilm

A
  1. organic/inorganic molecules + ions pre-condition the surface
  2. planktonic cells reversibly adhere to surface
    -initial attachment by adhesins surface proteins
    -hydrophobic/ hydrophilic + Van der Waals interactions
    -contact through pili/fimbriae
  3. nutrients available = cells irreversibly attach to surface
    -adhesive EPM
  4. cells begin to replicate + produce EPM
    -quorum sensing triggers binding to form microcolonies
  5. 2ndary colonizers partition the biofilm into niches/ water channels
  6. external parts of the biofilm may detach
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13
Q

dispersal is triggered by 3 major factors

A
  • starvation: depletion of C or N, intracellular starvation signals

-density: quorum sensing mediated release

-toxins: reactive oxygen species, particularly NO

mechanical stress can also cause biofilms to disperse

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14
Q

3 distinct varieties in which biofilm dispersal occurs

A
  • erosion: release of single cells or small clusters of cells at low levels
  • sloughing: sudden detachment of large portions of the biofilm
  • seeding: rapid release of a large number of cells following the formation of hollow, fluid-filled cavities inside biofilm
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15
Q

many bacteria produce hollow biofilms, filled with……and…..

A

fluids
planktonic cells

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16
Q

two main strategies for managing problematic biofilm formation

A
  1. inhibition
  2. dispersal
    -physical
    -chemical
    -enzymatic
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17
Q

3 main variables important to cell attachment, biofilm formation development

A
  1. adhesion surface
    -texture
    -charge
    -hydrophobocity
  2. bulk fluid
    -flow velocity
    -pH
    -temp
    -nutrient
  3. cell
    -appendages
    -EPM
    -signaling molecules
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18
Q

3 methods to get rid of biofilms

A

physical removal

chemicals to dissolve

enzymes to disperse

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19
Q

Shelford’s law of tolerance

A

max. and min. limits of an organism control their abundance and distribution

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20
Q

5 environmental stressors that bacteria

A
  1. pH
  2. temp
  3. osmolarity
  4. oxygen
  5. starvation
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21
Q

-log(Ka) =

A

pKa

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22
Q

when pH = pKa…..

A

concentration of dissociated and undissociated acids will be equal

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23
Q

when pH > pKA….

A

more molecules will dissociate

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24
Q

when pH < pKA….

A

fewer molecules will dissociate

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25
Q

all C-termini and N-termini can…..

A

donate/ accept protons

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26
Q

at pH > pKa…. amino acids will…..

A

donate protons

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27
Q

If the pH strays too far from optimum, the presence of H+ or OH– ions will disrupt……..

A

bonds in the tertiary structure

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28
Q

how can pH affect the properties of an R-group

A

electrostatic attraction between molecules of solution + R groups = decreased enzyme affinity

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29
Q

bacteria prevent denaturation or lowered enzyme affinity by…..

A

maintaining a consistent internal pH

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30
Q

neutrophile pH

A

internal 7.5-8
external 6-8

31
Q

acidophile pH

A

internal 6.5-7
external 1-4

32
Q

alkaliphile pH

A

internal 8.4-9
external 9-12

33
Q

true or false: acids can diffuse very quickly through the membrane bc of the negative charge

A

FALSE acids diffuse slowly c of the positive charge

34
Q

at low pH, concentration of H+ ions…….the pressure

A

increases

35
Q

To adapt to internal pH changes, bacteria must be able to do two different things:

A

alkalize cytoplasm
acidify cytoplasm

36
Q

4 ways to alkalize cytoplasm:

A
  1. proton pumping
  2. potassium pumping
  3. reduce membrane permeability
  4. produce ammonia
37
Q

2 ways to acidify cytoplasm:

A
  1. Na+/ H+ anti-porting
  2. K+/ H+ anti-porting
38
Q

if cytoplasm is too acidic, then….

A

more protons are pumped out than in

39
Q

………..limits the amount of H+ that can be moved to outside the cell

A

accumulation of + charges outside the cell

40
Q

to balance the internal charge when protons are pumped outwards, cells……

A

pump K+ ions back inside the cell

41
Q

saturated fatty acids are more hydro…… than unsaturated

A

hydrophobic

42
Q

saturated fatty acids are…….permeable to H+ ions

A

less

43
Q

bacteria can increase the pH with enzymatic……

A

activity

44
Q

example of enzymatic activity to increase pH

A

producing ammonia from urea with urease

45
Q

deaminase can increase pH by…….

A

removing the amine group from an amino acid or nucleotide

46
Q

alkaliphiles acidify the cytoplasm by…….

A

supplementing normal H+ pumping with Na+/ H+ anti-porters

47
Q

high temps cause proteins to……and membranes to become more…….

A

denature
permeable

48
Q

low temps……membrane permeability and……chemical reaction rates

A

reduce
reduce

49
Q

at higher temps, bacteria modify membrane fatty acids to contain…..saturated fatty acids

A

more

50
Q

saturated fatty acids have……melting points

A

higher

51
Q

many bacteria produce………to restore protein function after high temps

A

heat shock proteins (Hsps)

52
Q

newly synthesized proteins need the help of……. to fold into

A

chaperone proteins

53
Q

Hsp70

A

heat-shock chaperone protein that helps fold proteins using energy from ATP

54
Q

Hsp70 is activated by binding ATP, which…….

A

opens the active site to the unfolded polypeptide

55
Q

Hsp40

A

binds unfolded polypeptides and delivers them to Hsp70

56
Q

Hsp70 closes around the unfolded protein and provides energy from……and a suitable environment for protein folding

A

ATP hydrolysis

57
Q

a…….replaces ADP with ATP , which triggers Hsp70 to release the newly folded protein

A

nucleotide exchange factor

58
Q

in addition to folding new proteins, Hsp70 can…..

A

help refold denatured proteins

59
Q

unfolded proteins can form……usually due to exposed hydrophobic domains

A

aggregates

60
Q

some Hsps, like……. are able to disentangle aggregates before feeding polypeptides to Hsp70 and Hsp40

A

ClpB

61
Q

if misfolded proteins cannot be refolded, then……

A

they are degraded to prevent the toxic accumulation of aggregates

62
Q

there are at least……ATP-dependent proteases Hsp’s

A

6

63
Q

most bacteria live in ……tonic solutions

A

hypo

64
Q

turgor pressure

A

pressure exerted on the cell wall from water expanding inside the cell

65
Q

isotonic solution

A

no net movement of water

cell membrane attached to cell wall

66
Q

hypertonic solution

A

water particles move out of the cell

cell membrane shrinks and detaches from cell wall

shrunken cell

67
Q

hypotonic solution

A

water particles move into the cell

cell wall counteracts osmotic pressure swelling + lysis

68
Q

4 mechanisms bacteria use to respond to changes in osmolarity

A
  1. salting out
  2. accumulation of compatible solutes
  3. expression of aquaporins
  4. opening/ closing of mechanosensitive channels
69
Q

when turgor pressure is too high, bacteria can “salt-out” by……

A

trasnsporting Na+ out of the cell

70
Q

when turgor pressure is too low, bacteria…..

A

accumulate compatible solutes

71
Q

compatible solutes include

A

any non-toxic osmolytes in cytoplasm

can be organic or inorganic

72
Q

after increasing intracellular K+, cells…….

A

switch to other organic compatible solutes

sugars, poly-acids, amino acids

73
Q

osmolarity formula

A

osmolarity = moles ions/ L solution

microbio (5 decks)

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