Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

FDSC 442 > 16 - Biological Control of Foodborne Bacteria > Flashcards

16 - Biological Control of Foodborne Bacteria Flashcards

1
Q

what is biopreservation?

A

use of microorganisms, their metabolic products, or both to preserve foods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

is fermentation a form of biopreservation

A

usually not

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is controlled acidification?

A

acid is produced by the controlled growth of LAB “in situ” for temperature-abused foods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what examples of biopreservation are there?

A
  • controlled acidification
  • use of bacteriocins
  • use of bacteriophages
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what’s MicroGARD?

A

family of products that can be added to refrigerated food; contains fermentable CHO and bacterial culture; offers customizable protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

when is MicroGard effective?

A

only when food temperature is abused

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the benefits of using MicroGard?

A
  • protect shelf life
  • maintain organoleptic qualities in food
  • meet consumers’ demand for natural products
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what factors affect MicroGard’s effectiveness?

A
  • pH
  • buffering capacity
  • target spoilage microorganisms
  • concentration of fermentable CHO
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe the original experiment that determined the effectiveness of MicroGard

A

on “chicken a la king”

  • one sample was innoculated with LAB (L. bulgaricus and lactis)
  • the other was not
  • conditions simulated temp abuse
  • the one without LAB became toxic after 5 days
  • the one with LAB saw only 3/16 samples become toxic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what’s the wisconsin process?

A

pertains to bacon, which is normally preserved with nitrites. nitrites were found to produce carcinogenic derivatives.

this process replaces some nitrites with LAB, which makes the product less toxic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are bacteriocins?

A

antimicrobial peptides of bacterial origin that are lethal to some bacteria but not to the native host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

true or false: bacteriocins are antibiotics

A

false; bacteriocins are not antibiotics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is one concern regarding the use of bacteriocins?

A

development of bacteriocin-resistant pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what 4 classes can bacteriocins be divided into?

A
  • Class I
  • Class II
  • Class III
  • Class IV
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe class I bacteriocins

A

contain unusual amino acids produced by posttranslational modification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are some of the weird amino acids found in class I bacteriocins?

A
  • dehydroalanine
  • dehydrobutyrine
  • lanthionine
  • methyllanthione
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what’s a lantibiotic?

A

bacteriocin containing lanthionine rings (class I)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what’s nisin?

A
  • best-characterized LAB bacteriocin
  • obtained from L. lactis.
  • used in processing of cheese, meats, beverages, and more
  • extends shelf life by suppressing Gram-negative spoilage and pathogenic bacteria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what’s subtilin?

A
  • class I bacteriocin
  • a lantibiotic
  • effective protease that can be used in food, laundry detergent and contact lens cleaners
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

describe class II bacteriocins

A

small, heat-stable proteins with a consensus leader sequence that signals to the producing cell that the protein must be exported

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are the 3 subclasses of class II bateriocins?

A

IIa: active against listeria monocytogenes
IIb: require 2 different peptides for activity
IIc: require reduced cysteine for activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

describe class III bacteriocins

A

> 30 kDa, heat liable antimicrobial proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

describe class IV bacteriocins

A

have lipid or CHO moieties and function of these non-protein portions are unknown

24
Q

how are bacteriocins discovered?

A
  • overlay colony of bacteriocin producer over target bacteria
  • bacteriocin producers will form a sharp inhibitions zone
  • fuzzy edges are due to organic edges
  • zones with no colony in the center are due to bacteriophages
25
Q

what causes the formation of inhibition zones?

A
  • bacteriocins
  • organic acids
  • bacteriophage
  • H2O2
26
Q

how do you verify that a colony produces bacteriocins?

A

add protease to inactivate bacteriocin, enabling bacteria to grow in the zone it was originally inhibited

27
Q

how do bacteriocins work?

A
  • disrupt integrity of cytoplasmic membrane
28
Q

what does the addition of bacteriocins to vegetative cells do?

A

results in rapid, non-specific efflux of prea-accumulated ions, amino acids, and ATP molecules

29
Q

the efflux of pre-accumulated ions, AAs and ATP molecules does what to a cytoplasmic membrane?

A

rapidly dissipates chemical and electrical gradients; leads to cell inhibition and death

30
Q

true or false: ALL bacteriocins functions by the same mechanism

A

true

31
Q

most bacteriocins have ____ ____ ____ which allow for insertion into the membrane and permeabilization

A

amphiphilic cationic peptides

32
Q

what 2 models are proposed for bacteriocins to enter a cell?

A
  • pore formation model

- membrane solubilization model

33
Q

describe the pore formation model

A

bacteriocins bind, insert into the membrane, and oligomerize to form a pore

34
Q

describe the solubilization model

A

bacteriocins act as detergents resulting in lysis of the cell

35
Q

how do bacteriocins interact with spores?

A
  • allows (maybe encourages) spores to germinate
  • inhibits outgrowth of pre emergent spore
  • pre emergent spore is less resistant to environmental stresses than the spore
36
Q

what are colicins?

A

proteins produced by and are toxic to some strains of E. coli

37
Q

what does the plasmid bearing the genetic determinants for colicin production contain??

A
  • colicin synthesis
  • immunity
  • release
38
Q

colicin expression in under ….

A

SOS regulation, then released into extracellular medium

39
Q

what is the first step for a colicin to exert lethal action?

A
  • bind to specific receptors (outer membrane protein used for entry)
40
Q

how do colicins enter a membrane?

A

translocation through outer membrane and transit through the periplasm by either Tol or TonB system

41
Q

how do colicins reach/act their lethal target?

A
  • forming voltage-dependent channel into the inner membrane

- using endonuclease activity on DNA, rRNA, or tRNA

42
Q

how are colicins categorized?

A
  • enzymatic

- pore-forming

43
Q

what are some mode of actions for enzymatic colicins?

A
  • peptidoglycan synthesis block [M]
  • protein synthesis block by cleavage of tRNA [D and E5]
  • protein synthesis block by cleavage of 16S rRNA [E3, E4, and E6]
  • DNA degradation [E2, and E7 to E9]
44
Q

how are bacteriocins added to food?

A
  • bacteriocins added directly
  • bacteriocinogenic cultures can be added to non-fermented food products, bacteriocins are produced in situ
  • starter cultures that encode for bacteriocins can be chosen for fermentation reactions
45
Q

what bacteriocin is added directly to food?

A

Nisin (dairy products, canned foods, smoked fish, mayo, and baby foods)

  • anti-listerial properties
  • sensitizes spores to heat
  • used in foods where botulism is a concertn
46
Q

true or false: nisin is sufficient to add on its own

A

false: it’s usually added as part of a multiple-barrier inhibitory system; MAP storage
- delay toxin production by C. botulinum
- delay/stop growth of L. monocytogenes

47
Q

what bacteriocin is added to non-fermented food products?

A

Pediocins

48
Q

what do pediocins do?

A
  • active against VEGETATIVE monocytogenes cells (not spores)

- used in weiners

49
Q

what increases inhibition using bacteriocins?

A
  • lower temps

- greater anaerobic conditions

50
Q

which bacteriocin is added to fermentation products

A
  • pediocin in fermented sausage

- nisin in LAB strain in cheddar cheese

51
Q

how do bacteria become resistant to bacteriocins?

A

changes in membrane permeability. also:

  • destruction
  • modification
  • altered receptors
  • membrane composition
52
Q

how is bacteriocin resistance avoided?

A

use in combination with other hurdles

53
Q

true or false: nisin resistance is well studied

A

false

54
Q

what can bacteriophages do?

A

control growth of salmonella, e. coli, and listeria

55
Q

problem with using bacteriophages?

A
  • possible resistance

- low numbers of bacteria in food (phage needs 10^5 or 6 to be actively growing)

56
Q

how is resistance to bacteriophages developed?

A

changes in bacteriophage receptor site (proteins, LPS, or lipoproteins)

57
Q

how should be bacteriophages be administered?

A

as a cocktail containing several different strains and types

FDSC 442 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions