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Flashcards in Food Microbiology Deck (269)
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1

A gene with reversed orientation with respect to its regulatory sequence is called?

Antisense gene

2

A pool of DNA segments that is likely to contain a gene of interest is called a ____?

Genome library

3

A transgenic organism can be defined as what?

An organism containing foreign DNA

4

A thermal death curve is a plot of temperature versus log of the process time. What is the slope equal to?

-1/z

5

Allicin is an antimicrobial compound produced in what vegetable?

Onions/garlic

6

An enzyme called “coagulase” is produced by this pathogen which is highly correlated with its toxin production?

Staphylococcus aureus

7

An initial population of 50,000 bacteria grows with a generation time of 30 minutes. About how many bacteria 3 hours later?

3,200,000

8

A 6D process reduces the population of the target organism by what percent?

99.9999%

9

Chocolate creams have been known to undergo explosions. What is responsible for this phenomenon?

Clostridium species cause explosions after they enter the chocolate candy through sugars, starch and other ingredients

10

Clostridium welchhii is more commonly known as what?

Clostridium perfringens

11

Define “transformation”

The process of genetic transfer where bacteria are induced to accept and incorporate into their genome foreign pieces of cell-less, isolated DNA, often in the form of a plasmid.

12

Define a food infection.

Ingestion of organism and then the organism invades tissues in the body

13

What are the end products of a homofermentation by lactic acid bacteria?

Homofermentative - glucose fermented to > 90% lactic acid

14

Define D Value

Time needed to inactivate 1 log cycle of a population (or a 1 decimal reduction) at a given temperature or time needed to reduce a population to 10% of the original

15

Define fecal coliforms and indicate the reason that they are often evaluated in foods.

Gram negative, asporogenous rods that ferment lactose to acid and gas at 44.5 to 45.5 C

16

DNA obtained by cutting and recombining DNA molecules from different sources is called?

rDNA (recombinant DNA)

17

DNA sequence variations that occur when a single nucleotide in the genome sequence is altered is called what?

Single Nucleotide Polymorphisms (SNPs)

18

During which phase of microbial growth may bacteria be most easily killed?

Log phase

19

Enzymes that catalyze the hydrolysis of ester linkages in triacyglycerides are called what?

Lipases

20

Every microbiology student knows it’s the Bible of Bacterial Taxonomy. What is it?

Bergey’s Manual

21

For what does BRC stand and what is it?

British Retail Consortium; food safety standards system

22

For what does MPN stand?

Most Probable Number

23

Fresh Mexican style cheese was the vehicle for an outbreak in California in 1985 in which 300 persons became ill and almost 100 of them died. What organism, found in the finished product and throughout the plant, was responsible for this outbreak?

Listeria monocytogenes

24

Give three sites of action for antimicrobials.

Cell wall; cell membrane; genetic mechanism or functions; interfering with enzyme systems; binding essential nutrients

25

Give two microorganisms responsible for scombroid poisoning (histamine) in seafood?

Morganella spp., especially Morganella morganii; Others include: Proteus spp., Klebsiella pneumoniae, Clostridium perfringens, Hafnia alvei

26

How does pH negatively affect microorganisms?

Influence availability of metallic ions; cell permeability to cations and anions; affects tRNA and protein synthesis; activities of enzyme systems; products of metabolism of microorganisms

27

How is fungi differentiated from algae and other higher plants?

Lack of chlorophyll

28

How many primer(s) is(are) used in a loop-mediated isothermal amplification assay?

4 to 6

29

How many square centimeters in a standard 9 cm Petri dish?

64 cm2

30

If a food processor chooses potassium sorbate over sorbic acid it would probably because it is what: less toxic, more heat stable, more water soluble, less water soluble

More Soluble in water than in Sorbic acid