Brainscape's Knowledge GenomeTM

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


See full index

Food-Borne Pathogens > Final Exam > Flashcards

Final Exam Flashcards

1
Q

How are food ecosystems impacted?

A

By generation and utilization of energy

Affect host ecosystems when ingested

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

What are intrinsic food ecosystems?

A 
Factors inherent to the food:
pH
Aw
Nutrients
Changes over time as bacteria grow and produce by-products
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are extrinsic food ecosystems?

A

Factors external to the food:
Temp
Gases in atmosphere
Change over time as bacteria grow and produce by-products

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

What are the stages of bacterial growth & division?

A

Lag phase (no growth; min number)
Log/exponential growth phase
Stationary phase (no growth; max number)
Deat/logarithmic decline phase

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

What are the requirements for bacterial growth and division?

A

Carbon (anabolism)
Energy (catabolism)
Source of electrons
Electron acceptor

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

What are the types of carbon for bacterial building?

A

Autotrophic: carbon from CO2 carbon fixation
Heterotropic: carbon from organic compounds
Mixotrophic: both auto & heterotrophy

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

What are the types of energy sources of bacteria?

A

Chemotrophic: energy from external chemical compounds
Phototrophic: energy from light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the types of sources of electrons for bacteria?

A

Lithotrophic: reducing equivalents from inorganic compounds
Organotrophic: reducing equivalents from organic compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the types of electron acceptors?

A

Aerobic organisms: use oxygen
Fermentation: use organic carbon (fermentative organisms = anaerobes)
- Succinate fermentation or oxalate fermentation: low energy-yielding fermentation forms
Facultative anaerobes: grow with or without oxygen
Strict anaerobes:
- Denitrification: nitrate
- Sulfate reduction: sulfate
- Acetogenesis: CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Lactic acid bacteria:

A

Produce relatively large quantities of lactic acid from carbohydrates

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

Proteolytic bacteria:

A

Hydrolyze proteins in food to produce extracellular proteinases

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

Lipolytic bacteria:

A

Hydrolyze triglycerides to produce extracellular lipases

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

Types of bacteria based on temperature:

A

Thermophilic: can grow above 50C
Thermoduric: can survive pasteurization temps
Psychotropic: can grow at fridge temp
Cryophilic: can grow at freezer temp

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

Halophilic bacteria:

A

survive high salt (above 10%) concentrations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Aciduric bacteria:

A

Survive low pH

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

Osmophilic bacteria:

A

Grow at higher osmotic environments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the difference between coliforms and fecal coliforms?

A

Both: used as an index for sanitation

Fecal coliforms: presence indicates fecal contamination

18
Q

What are enteric pathogens?

A

Can cause gastrointestinal infection

19
Q

What is the number of bacteria in meat?

A

Right after slaughter: 10^1-3cells/inch
Ground meat: 10^4-5cells/gram
Heat processed: 10^1-2cells/gram

20
Q

What is the main bacterial issue to meat?

A

Psychotrophic bacteria (ex. Listeria)
Due to meat being chilled during storage
Many heat processed meats to reduce bacteria & increase shelf life (over 50 days)
- Can be stored anaerobically

21
Q

What is the number of bacteria in raw milk?

A

Raw milk: 10^3 cells/mL
- Higher in cows with mastitis
Pastuerizaed milk: 10^4cells/mL

22
Q

What causes milk to be good for microbial growth?

A

High in carbs (lactose) & protein

- Carbon and energy sources

23
Q

What best bacteria grow in milk?

A

Before pasteurization = psychotrophs

After pasteurization = thermodurics & bacteria that enter post pasteurzation (from equipment, handling, air…)

24
Q

Why are fish and shellfish good or bad for bacterial growth?

A 
Good:
- High in protein 
- High Aw, pH
- Availalbe carbon and nitrogen
Bad:
- Low in fat & carbs
- HIgh in salt (need halophiles)
25
Q

What makes vegetables, fruits, and nuts good/bad for bacterial growth?

A 
High in carbs
Stored at room temp
pH:
- Veggies = 5-7
- Fruits = 4.5 or lower
26
Q

How much bacteria is in vegetables and fruit?

A 
Veggies = 10^4-7 cells/gram
Fruits = 10^3-4 cells/gram
27
Q

Why is pH important in canned foods?

A

If below 4.6 = mesophiles germinate & produce toxins

If above 4.6 = mesophiles not an issue unless temperature abused

28
Q

What major pathogen is in canned foods?

A

Staphylococcus

The toxins can survive canning process

29
Q

What is the cell membrane responsible for?

A

Solute transport
Electron transport
Establishment of electrochemical gradients
ATP synthesis
Synthesis of lipids
Secretion of proteins
Secretion & uptake of intercellular signals

30
Q

Why does turgor pressure exist on bacteria?

A

Bacteria live in environments that are more dilute than the cytoplasm
Causes net influx of water, resulting in pressure being directed out against the cell wall

31
Q

What is the difference between gram-negative & gram-positive bacteria?

A 
Gram + 
- Peptidoglycan cell wall (w/ Lipoteichoic acid comprising 30-60% of weight)
- Plasma membrane 
- Fimbrae & pili in very few
Gram -
- Outer lipid membrane (w/ lipopolysaccharide consisting lipid A, core, & O antigen)
- Peptidoglycan
- Plasma membrane
- Fimbrae & pili in most
32
Q

What is the process of the gram stain?

A
  1. Apply crystal violet (purple)
  2. Apply iodine (to bind crystal violet to gram +)
    - Traps crystal violet in peptidoglycan of gram + (called mordant)
  3. Wash in alcohol to remove from gram -
  4. Add safranin (counterstain pink)
    - Binds to gram - to see under light microscope
33
Q

Function of fimbrae & pili:

A

Mediate attachment to cells
Mediate genetic exchance
Transmit DNA

34
Q

Types of pili:

A

Adhesive pili: have adhesins
Sex pili: attach to each other & transmit DNA from a donor cell
- Found in enteric bacteria (not universal)
- Ex. F plasmid contains code for sex pili in E. coli

35
Q

What are the serotypes based on cell surface structures?

A 
K antigen (capsule)
O antigen (lipopolysaccharide)
F antigen (fimbriae)
H antigen (flagella)
* typing scheme differs between each type of bacteria
36
Q

What are injured cells?

A

Due to sublethal stressors
Unable to grow on selective media, but can grow on non-selective media
- More sensitive to selective agents & may have increased nutritional requirements

37
Q

Why are injured cells important in food microbiology?

A
  • If they appear dead, resistance will be underestimated & the “kill” values will be low
  • May escape detection post-processing, leading to faster spoilage
  • “selective agent” can be a common food ingredient such as sald, organic acid, or suboptimal temperatures
38
Q

How are injured cells repaired?

A

Required new RNA & protein synthesis
May seem an extended lag phase
Reestablishes membrane integrity
Temperature is critical (can be delayed w/ suboptimal temp)
Peroxide detox agent can help damage from oxygen toxicity

39
Q

What is VBNC?

A

Viable but not culturable
- Can’t be cultured on any media
Survival strategy for non-sporulating species
- Ex. Salmonella, Campylobacter, Excherichia, Shigella, Vibrio
Morphologically different from a normal vegetative cell
Caused mostly by nutrient limitation; also by salt concentration, chemicals, or temp shifts
- Removed by temp shifts and gradual return of nutrients
Up to 99% of bacteria can be unculturable

40
Q

How can VBNC cells be demonstrated?

A

Cytological methods

Substrate responsive metabolism

41
Q

How is VBNC demonstrated through cytological methods?

A

Structural integrity indicates life, deteriation indicates cell death
Fluorescent nucleic acid stains (red) are added
- If permeate cell, deterioration occurred & cell is dead
Color stain used for cell wall (green)
- If cell wall is intact will see green; if deteriorated will see red

42
Q

How is VBNC demonstrated through substrate responsive metabolism?

A

Incubated with a ntureint and an antibiotic
- Inhibits cell division
Live cells elongate but do not divide
* used for Lm

Food-Borne Pathogens (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions