Final Exam Review Session Flashcards
what’s the difference between microbiome and the microbiota?
microbiome encompasses microbiota. if the environment is alive, it’s a microbiota. if it’s not living (a rock), then it’s a microbiome.
what’s the difference between 16S rRNA targeted amplicon sequencing and metagenomics?
16S tells you what type of phylogeny you have why metagenomics tells you what they’re capable of doing
what’s a probiotic? abiotic? prebiotic? synbiotic
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
differentiate between autochthonous microbiota and the allochthonous microbiota
auto = always there allo = acquired
definition of spoiled as it refers to food?
sensorily unacceptable according to consumer standard
what is scombroid food poisoning?
comes from fish products from the decarboxylation of histidine to histamine, causing allergy-like symptoms
what’s ethylene?
gas produced by produce that speeds up ripening
what’s an appressorium?
a fungus’s way of penetrating a plant’s defenses
what’s a phytoalexin?
“plant immune system” - inhibits the growth of parasites
explain the relationship between the D value, Z value, and F value
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
what value is most important to the commercial canning industry?
F value - we want a specific reduction
compare/contrast aseptic processing with canning
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.
what’s a humectant?
substance used to retain moisture in foods
define radappertization, radicidation, and radurization
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
what does HPP stand for?
high pressure processing
define biopreservation
use of microorganisms to control the growth of spoilage/pathogenic microorganisms (excludes fermentation)
what is controlled acidification?
add microbes that produce acid to lower acid and control activity of other microbes
what is the Wisconsin process?
adding LAB to bacon to replace some use of nitrites for prevention of C. botulinum growth
define bacteriocin
peptide produced by bacteria to prevent other bacteria from growing
what is colicin?
bacteriocin produced by and used against specific coliforms
legally, how is food adulteration defined
adding something of lesser value to something with greater value to deceive the consumer
what is the importance of the 16S rRNA gene
- all bacteria have it
- closely linked to phylogeny as it evolves slowly
- good for identification
what are the 6 criteria for the selection of probiotic strains?
1) origin
2) biosafety
3) tolerance to acid/bile salts
4) Adhesion to intestinal cells
5) production of antimicrobial substances
6) utilization of prebiotics
what’s the significance of E. coli Nissle?
not a pathogen - it’s there to compete with other bacteria and prevent pathogenic E. coli from entering. it’s a probiotic
are S. thermophilus and L. bulgaricus probiotics?
can be argued
yes: aid in lactose digestion
no: have little to no hang time in GI tract
is L. rhamnosus GR1 a probiotic?
yes, it reduces UTIs
if you discover a new bacteria, can you immediately market it as a probiotic in canada?
no, you have to show evidence to HC to show it has benefits
is spoiled food safe to eat?
sometimes
which genus of bacteria is considered to be the best at attaching to meat
Pseudomonas
what are some signs of microbial spoilage?
- small
- greening
- cloudiness
- ropiness
what are some characteristics of ideal spoilage indicators?
- be absent in fresh tissues
- be produced by spoilage flora
- increases with storage time
- correlate well with sensory analysis
what happens if an animal is exercised before slaughter?
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
how does the lactoperoxidase system work?
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
is it important to refrigerate milk prior to pasteurization?
yes - pasteurization doesn’t sterilize, it only reduces the load by a log. if not refrigerated, some surviving bacteria can produce toxins
what is the difference between refrigerated/temperature abused milk spoilage?
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.
which method of preservation is the most common?
physical methods (temperature control)
why aren’t microwaves good for use in food processing facilities?
they don’t distribute heat evenly
explain the relationship between low temperature preservation and xerotolerant microorganisms
xerotolerant microorganisms can withstand dryness. in frozen conditions, there is no water available, which is conducive to xerotolerant organisms.
explain the difference between water availability and moisture content.
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.
what types of organisms grow at an aw of low and high
high aw (above 0.87): bacteria
yeasts can survive at lower aw than bacteria
mold are xerotolerant (above 0.61)
are most chemical preservatives bacteriostatic or bactericidal?
static
why are weak organic acids more effective than strong organic acids?
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
name four weak, monoprotic organic acids
acetic, lactic, propionic, sorbic, benzoic (i know that’s 5)
what would be a good organic acid to add to wine prior to bottling as a preservative
sorbic
what is the mechanism for antibacterial activity of sulfites such as sodium metabisulfite (Campden crush)
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
common source of allicin?
garlic & onion
what are 3 examples of methods of biopreservation?
- bacteriocins
- bacteriophages
- controlled acidification
- MicroGARD
- Wisconsin Process
what are the 3 key benefits of MicroGARD?
- protect shelf life
- maintain organoleptic qualities of food
- meet consumer demand for “natural” products
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?
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.
name a common bacteriocin used in foods
nisin
why aren’t bacteriophage more commonly used as preservatives?
- Consumer perception
- potential development of resistance
- requires a higher concentration of bacteria to work, which isn’t so common in food
which class of antibiotics was discovered within the last 10 years?
teixobactin
is it common to find AMR in food?
yes
compare and contrast bactericidal and bacteriostatic antibiotics. what are some examples of each? what mechanisms are used?
- 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
does AMR in the food chain cause more AMR infections in humans?
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.
how quickly can bacteria obtain AMR?
within hours
which antibiotic does the mcr-1 gene provide resistance to?
colistin
i just isolated a new bacterium, how could i assess if this bacterium has any AMR?
well assay, strip assay, whole genome sequencing
what microorganism was used in the largest bioterror attack to-date in the US
Salmonella
why is CARVER+shock used?
evaluates the vulnerability of a food operation system by evaluating each node within it
what are the 7 elements of CARVER+Shock analysis?
1) criticality
2) accessibility
3) recuperability
4) vulnerability
5) effect
6) Recognizability
7) Shock
what are the 3 parts of the Codex Alimentarius risk analysis framework?
- risk assessment
- communication
- management
Why did CBC report eh 2008 outbreak 10 days before PHAC did? was this a good idea?
PHAC was unsure of the source of the outbreak.
no - this was bad because it could have prevented some cases
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
b) E. coli Nissle
