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Food Borne Pathogens > Lecture 1- Food is an Ecosystem > Flashcards

Lecture 1- Food is an Ecosystem Flashcards

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1
Q

Anaerobic Metanogens

A

Eat CO2

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2
Q

Phototrophs

A

Eat sunlight/CO2, produce O2

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3
Q

Anaerobic Metanogens

A

Make CH4

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4
Q

Aerobic Methanotrophs

A

Eat CH4

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5
Q

Aerobic Methanotrophs

A

Makes CO2

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6
Q

Ecosystem

A

is a series of interactions between the environment and the organisms that inhabit it

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7
Q

Food ecosystems are composed of intrinsic and extrinsic factors. What are intrinsic factors?

A

Factors inherent to the food (pH, water activity, nutrients)

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8
Q

Definition of extrinsic factors

A

Factors external to the food (temperature, gaseous atmosphere)

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9
Q

What is the usual growth of bacteria (think of graph)

A

Lag phase: plateau
Log, or exponential growth, phase
Stationary phase
Death, or logarithmic decline, phase

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10
Q

Autotrophic

A

Carbon from CO2 through carbon fixation

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11
Q

Heterotrophic

A

Carbon from organic compounds

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12
Q

Mixotrophic

A

can combine auto and heterotrophy

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13
Q

Chemotrophic

A

energy is obtained from external chemical compounds

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14
Q

Phototrophic

A

energy is obtained from light

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15
Q

Lithotrophic

A

reducing equivalents come from inorganic compounds

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16
Q

Organotrophic

A

reducing equivalents come from organic compounds

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17
Q

Aerobic organisms

A

use O2 as a terminal electron acceptor (this is the most energetically favorable reaction)

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18
Q

Fermentation

A

use organic carbon as a terminal electron acceptor, therefore, fermentative organisms are considered anaerobes

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19
Q

Facultative anaerobes

A

an organism that can grow with or without oxygen

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20
Q

What are the 4 things that bacteria need to have to grow and divide?

A
  1. Must have carbon for building the array of chemical substances of which they are composed (anabolism)
  2. Bacteria must have a source of energy for living (catabolism)
  3. Must have a source of electrons to be used in energy conservation and biosynthetic reactions
  4. Must have an electron acceptor
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21
Q

Denitrification

A

nitrate as an electron acceptor

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22
Q

Sulfate Reduction

A

sulfate as an electron acceptor

23
Q

acetogenesis

A

CO2 as an electron acceptor

24
Q

Lactic Acid Bacteria

A

Produce large quantities of lactic acid from CHO

25
Q

Proteolytic Bacteria

A

hydrolyze PRO in food because they produce extracellular proteinases

26
Q

Lipolytic bacteria

A

hydrolyze TGs because they produce extracellular lipase

27
Q

Termophilic bacteria

A

bacteria that are able to grow > 50C

28
Q

Thermoduric Bacteria

A

able to survive pasteurization temps

29
Q

Psychrotrophic bacteria

A

able to grow at refrigerated temps (<5C)

30
Q

Cryophilic bacteria

A

able to grow at freezer temp. (<0C)

31
Q

Halophilic bacteria

A

able to survive high salt concentrations (>10C)

32
Q

Aciduric bacteria

A

able to survive low pH

33
Q

Osmophilic bacteria

A

able to grow at a higher osmotic environment

34
Q

Spore formers

A

able to produce spores

35
Q

Coliforms

A

used as an index for sanitation

36
Q

fecal coliforms

A

used as an index for sanitation, presence indicates fecal contamination

37
Q

enteric pathogens

A

can cause gastrointestinal infection

38
Q

What organism is the main issue when meat is stored chilled?

A

psychotropic organisms like listeria

39
Q

What organism can be present in heat processed meats like lunch meat?

A

Since these products can be stores anaerobically, pychrotrophic facultative anaerobes may dominate

40
Q

What type of organism is responsible for spoilage in non-temperature abused milk?

A

Psychrotrophs

41
Q

Why can microorganism grow rapidly in fish?

A

fish have high water availability, pH of the tissue, and the availability of C and N

42
Q

What pH must you can your food for it to be safe from Clostridium?

A

lower than 4.6

43
Q

Can staphylococcus toxin survive the canning process?

A

Yes, toxin can survive the process of canning and cause food poisoning following the consumption of the product

44
Q

Injured cells

A

more sensitive to selective agents (antibiotics) and may have increased nutritional requirements

45
Q

Microbial injury is important in food microbiology for several reasons (3)

A
  1. If injured cells appear dead due ti the use of selective media in thermal studies, the thermal resistance will be underestimated and the true “kill” values will be low
  2. Injured cells make escape routine detection post-processing leading to faster spoilage or a safety problem
  3. the “selective agent” may be a common food ingredient such as salt, organic acid, or suboptimal temperature
46
Q

Viable But not Culturable (VBNC) and examples

A

VBNC- a state in which cells cannot be cultured on any media even though their viability can be demonstrated by non-culturable methods
It is a survival strategy for non-sporulating species
During transition rod shaped cells shrink and become spherical bodies
EX: Salmonella, Campylobacter, E.coli, Shigella, Vibrio

47
Q

How do you demonstrate that the cells are still viable through cytological methods? (3)

A
  1. Structural integrity of the bacterial cytoplasmic membrane indicated life, while deterioration of this membrane indicates that the cell is dead
  2. Fluorescent nucleic acid strains (red) are incubated with cells, if they permeate the cell it indicates the cell is dead
  3. Counter stain is used to stain the cell wall (green). Bacteria with intact cell membranes stain free, whereas bacteria with damaged membranes stain red
48
Q

How doe you demonstrate that the cells are still viable through substrate responsive metabolism? (2)

A
  1. Cells can be incubated with a nutrient and an antibiotic that inhibits cell division
  2. live cells elongate, but do not divide
49
Q

Can VBNC be resuscitated? If so, how?

A

Yes, by temperature shifts and a gradual return of nutrients.

50
Q

Cellular communication: Signal Transduction

A

two component regulatory systems where one PRO spans the membrane, picks up a signal and then reacts based on a response regulatory PRO
Who uses it?: L monocytogenes, S.aureus, Lactic acid

51
Q

Cellular communication: Quorum Sensing

A

Systems are built on autoinducers which diffuse through the cellular membrane to initiate a specific response when a certain population density has been reached
Who uses it? S. enteric, E.coli, V. cholerae

52
Q

Pleiotrophic

A

occurs when one gene influences two or more seemingly unrelated phenotypic traits

53
Q

Biofilms

A

aggregation of cells, often of multiple species, into heterogeneous complex structures that are attached to a solid surface
More resistance to heat, chemicals and sanitizers the planktonic cells, making them imp. to the food industry

54
Q

Endospores

A

differentiated cells that are very resistance to heat and cannot be easily destroyed, even by chemicals

Food Borne Pathogens (14 decks)

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