Final Exam Review Session

Question 1

what’s the difference between microbiome and the microbiota?

Answer 1

microbiome encompasses microbiota. if the environment is alive, it’s a microbiota. if it’s not living (a rock), then it’s a microbiome.

Question 2

what’s the difference between 16S rRNA targeted amplicon sequencing and metagenomics?

Answer 2

16S tells you what type of phylogeny you have why metagenomics tells you what they’re capable of doing

Question 3

what’s a probiotic? abiotic? prebiotic? synbiotic

Answer 3

probiotic = living organism that helps in digestion
abiotic = inactive organism that still provides benefits
prebiotic = food for the microorganisms
synbiotic = supplement or ingredients that contains both a pro and prebiotic

Question 4

differentiate between autochthonous microbiota and the allochthonous microbiota

Answer 4

auto = always there
allo = acquired

Question 5

definition of spoiled as it refers to food?

Answer 5

sensorily unacceptable according to consumer standard

Question 6

what is scombroid food poisoning?

Answer 6

comes from fish products from the decarboxylation of histidine to histamine, causing allergy-like symptoms

Question 7

what’s ethylene?

Answer 7

gas produced by produce that speeds up ripening

Question 8

what’s an appressorium?

Answer 8

a fungus’s way of penetrating a plant’s defenses

Question 9

what’s a phytoalexin?

Answer 9

“plant immune system” - inhibits the growth of parasites

Question 10

explain the relationship between the D value, Z value, and F value

Answer 10

D = time it takes for 1 log reduction
Z = temperature change to cause 1 log reduction
F = time it takes to achieve a specified concentration

Question 11

what value is most important to the commercial canning industry?

Answer 11

F value - we want a specific reduction

Question 12

compare/contrast aseptic processing with canning

Answer 12

canning: stick stuff in a jar then sterilize the whole system
aseptic processing: sterilize food and containers separately, then fill sterile containers with sterile food in sterile conditions.

Question 13

what’s a humectant?

Answer 13

substance used to retain moisture in foods

Question 14

define radappertization, radicidation, and radurization

Answer 14

radapp = high dose to achieve commercial sterility
radicidation = medium dose. achieves similar effect as thermal pasteurization
radurization = low dose to control insects and prevent sprouting and ripening

Question 15

what does HPP stand for?

Answer 15

high pressure processing

Question 16

define biopreservation

Answer 16

use of microorganisms to control the growth of spoilage/pathogenic microorganisms (excludes fermentation)

Question 17

what is controlled acidification?

Answer 17

add microbes that produce acid to lower acid and control activity of other microbes

Question 18

what is the Wisconsin process?

Answer 18

adding LAB to bacon to replace some use of nitrites for prevention of C. botulinum growth

Question 19

define bacteriocin

Answer 19

peptide produced by bacteria to prevent other bacteria from growing

Question 20

what is colicin?

Answer 20

bacteriocin produced by and used against specific coliforms

Question 21

legally, how is food adulteration defined

Answer 21

adding something of lesser value to something with greater value to deceive the consumer

Question 22

what is the importance of the 16S rRNA gene

Answer 22

• all bacteria have it
• closely linked to phylogeny as it evolves slowly
• good for identification

Question 23

what are the 6 criteria for the selection of probiotic strains?

Answer 23

1) origin
2) biosafety
3) tolerance to acid/bile salts
4) Adhesion to intestinal cells
5) production of antimicrobial substances
6) utilization of prebiotics

Question 24

what’s the significance of E. coli Nissle?

Answer 24

not a pathogen - it’s there to compete with other bacteria and prevent pathogenic E. coli from entering. it’s a probiotic

Question 25

are S. thermophilus and L. bulgaricus probiotics?

Answer 25

can be argued yes: aid in lactose digestion no: have little to no hang time in GI tract

Question 26

is L. rhamnosus GR1 a probiotic?

Answer 26

yes, it reduces UTIs

Question 27

if you discover a new bacteria, can you immediately market it as a probiotic in canada?

Answer 27

no, you have to show evidence to HC to show it has benefits

Question 28

is spoiled food safe to eat?

Answer 28

sometimes

Question 29

which genus of bacteria is considered to be the best at attaching to meat

Answer 29

Pseudomonas

Question 30

what are some signs of microbial spoilage?

Answer 30

- small - greening - cloudiness - ropiness

Question 31

what are some characteristics of ideal spoilage indicators?

Answer 31

- be absent in fresh tissues - be produced by spoilage flora - increases with storage time - correlate well with sensory analysis

Question 32

what happens if an animal is exercised before slaughter?

Answer 32

glucose is converted to lactic acid in the muscle which changes spoilage events. leads to faster degradation of amino acids and detection of spoilage at lower bacterial cell densities

Question 33

how does the lactoperoxidase system work?

Answer 33

works best with the addition of H2O2. lactoperoxidase catalyzes the oxidation of thiocyanate and makes hypothiocyanite, which is an oxidant that functions as an antimicrobial

Question 34

is it important to refrigerate milk prior to pasteurization?

Answer 34

yes - pasteurization doesn't sterilize, it only reduces the load by a log. if not refrigerated, some surviving bacteria can produce toxins

Question 35

what is the difference between refrigerated/temperature abused milk spoilage?

Answer 35

refrigerated: spoiled by psychrotrophic bacteria, especially Pseudomonas. Defects are a result of extracellular enzymes that do proteolysis (bitter/putrid) and lipolysis (rancid/fruity). temperature abused: wild LAB. makes off tastes due to acetic and propionic acids.

Question 36

which method of preservation is the most common?

Answer 36

physical methods (temperature control)

Question 37

why aren't microwaves good for use in food processing facilities?

Answer 37

they don't distribute heat evenly

Question 38

explain the relationship between low temperature preservation and xerotolerant microorganisms

Answer 38

xerotolerant microorganisms can withstand dryness. in frozen conditions, there is no water available, which is conducive to xerotolerant organisms.

Question 39

explain the difference between water availability and moisture content.

Answer 39

moisture content describes the amount of water in a food item, accounting for all of its forms (free, bound) water availability refers to only the free water available for microbial/enzymatic use.

Question 40

what types of organisms grow at an aw of low and high

Answer 40

high aw (above 0.87): bacteria yeasts can survive at lower aw than bacteria mold are xerotolerant (above 0.61)

Question 41

are most chemical preservatives bacteriostatic or bactericidal?

Answer 41

static

Question 42

why are weak organic acids more effective than strong organic acids?

Answer 42

weak acids are undissociated outside the cell and can pass through cell membranes. once inside, they dissociate and kill the cell by wasting its energy on efflux pumps or by damaging proteins and DNA nearby

Question 43

name four weak, monoprotic organic acids

Answer 43

acetic, lactic, propionic, sorbic, benzoic (i know that's 5)

Question 44

what would be a good organic acid to add to wine prior to bottling as a preservative

Answer 44

sorbic

Question 45

what is the mechanism for antibacterial activity of sulfites such as sodium metabisulfite (Campden crush)

Answer 45

aqueous solutions of sulfur dioxide can yield sulfurous acid (H2SO3) which works in a similar method to organic acids SO2 can also: - rupture sulfide bridges - inhibit rxns w/cofactors - deaminate cytosine to uracil leading to likely fatal mutations

Question 46

common source of allicin?

Answer 46

garlic & onion

Question 47

what are 3 examples of methods of biopreservation?

Answer 47

- bacteriocins - bacteriophages - controlled acidification - MicroGARD - Wisconsin Process

Question 48

what are the 3 key benefits of MicroGARD?

Answer 48

- protect shelf life - maintain organoleptic qualities of food - meet consumer demand for "natural" products

Question 49

if i wanted to screen a population of bacteria for one that was capable of producing a bacteriocin against E. coli, how would i do that?

Answer 49

overlay a colony of this bacteria with an agar medium containing E. coli. If a zone of inhibition is made with sharp edges and a colony in the middle, it produced a bacteriocin. this is verified by poking the colony of interest and filling the hole with proteases, which should allow bacteria to grow there now.

Question 50

name a common bacteriocin used in foods

Answer 50

nisin

Question 51

why aren't bacteriophage more commonly used as preservatives?

Answer 51

- Consumer perception - potential development of resistance - requires a higher concentration of bacteria to work, which isn't so common in food

Question 52

which class of antibiotics was discovered within the last 10 years?

Answer 52

teixobactin

Question 53

is it common to find AMR in food?

Answer 53

yes

Question 54

compare and contrast bactericidal and bacteriostatic antibiotics. what are some examples of each? what mechanisms are used?

Answer 54

- bactericidal: kills everything. ex: B-lactam, aminoglycosides, quinolones. they target cell structures (biosynthesis of the cell wall or DNA) - bacteriostatic: inhibits further growth. ex: macrolides, telithromycin, sulfonamides, tetracycline. they target protein synthesis

Question 55

does AMR in the food chain cause more AMR infections in humans?

Answer 55

can be argued yes: AMR is common in food for both pathogens and commensal bacteria. therefore the genepool must be high and it is likely for humans to be exposed to AMR genes. no: the actual number of pathogens in food is very small, and ARM pathogens is even smaller. It's hard to say whether these genes actually move to organisms in the GI tract.

Question 56

how quickly can bacteria obtain AMR?

Answer 56

within hours

Question 57

which antibiotic does the mcr-1 gene provide resistance to?

Answer 57

colistin

Question 58

i just isolated a new bacterium, how could i assess if this bacterium has any AMR?

Answer 58

well assay, strip assay, whole genome sequencing

Question 59

what microorganism was used in the largest bioterror attack to-date in the US

Answer 59

Salmonella

Question 60

why is CARVER+shock used?

Answer 60

evaluates the vulnerability of a food operation system by evaluating each node within it

Question 61

what are the 7 elements of CARVER+Shock analysis?

Answer 61

1) criticality 2) accessibility 3) recuperability 4) vulnerability 5) effect 6) Recognizability 7) Shock

Question 62

what are the 3 parts of the Codex Alimentarius risk analysis framework?

Answer 62

- risk assessment - communication - management

Question 63

Why did CBC report eh 2008 outbreak 10 days before PHAC did? was this a good idea?

Answer 63

PHAC was unsure of the source of the outbreak. | no - this was bad because it could have prevented some cases

Question 64

Which probiotic strain appears to offer some protection against urinary tract infections when taken orally? a) acetobacter b) E. coli Nissle c) Lactobacillus rhamnosus GR1 d) Bifidobacteria longum UTI

Answer 64

b) E. coli Nissle