Lab Quiz 7: Thermal Death Curves, Ultraviolet Light, Water Quality Testing, Genetic Transformation (Bio 286 - Microbiology)

Question 1

D-value

Answer 1

conditions (time, temperature, etc) that results in a reduction of the bacterial population by 90%… ie ONLY 10% (one log) of the viable cells remain

Question 2

thermal death time

Answer 2

the shortest amount of time needed to kill all viable cells at a given temperature

Question 3

thermal death point

Answer 3

the lowest temperature needed to kill all viable cells in a given time

Question 4

thermal death time on chart

Answer 4

the first time column containing a (-) at a given temperature

Question 5

thermal death point on chart

Answer 5

the first temperature row containing a (-) at a given time

Question 6

Bacillus cereus

Answer 6

had the highest thermal death point and is arguably heat tolerant (most likely due to its capability of forming endospores, which are resistant to heat)

Question 7

shorter wavelength radiation

Answer 7

has more energy, has a higher frequency, has greater penetrating power, and is more biologically damaging

Question 8

longer wavelength radiation

Answer 8

has less energy, has a lower frequency, has lower penetrating power, and is less biologically damaging

Question 9

ultraviolet light

Answer 9

shorter wavelength than visible light (100-400 nm) and can be used as germicidal treatment; three sub-spectra: UVA, UVB, UVC

Question 10

UVA (Ultraviolet A)

Answer 10

wavelengths between 315-400 nm; gives suntans and are the least damaging; partially removed from solar spectrum by ozone in atmosphere

Question 11

UVB (Ultraviolet B)

Answer 11

wavelengths between 280-315 nm; more damaging and can cause sunburns and skin cancer; most is removed by ozone

Question 12

UVC (Ultraviolet C)

Answer 12

wavelengths between 100-280 nm; most damaging; completely removed from sunlight by ozone

Question 13

260 nm

Answer 13

most germicidal wavelength of UV light; within UVC range

Question 14

most resistant to UV light

Answer 14

bacillus cereus (due to its endospore formation)

Question 15

most susceptible to UV light

Answer 15

staphylococcus aureus

Question 16

intermediate susceptibility to UV light

Answer 16

pseudomonas aeruginosa (produces protective green pigment) and serratia marcescens (produces protective red pigment)

Question 17

if the covers on the petri dishes had not been removed

Answer 17

the cells within the petri dishes would not have been exposed to UV light and would most likely grow unencumbered (UV light cannot pass through petri dish covers)

Question 18

indicator organisms

Answer 18

always present when feces are present (PRESENT IN FECES); should be absent when feces are absent (ABSENT WITHOUT FECES); organism should be very EASY TO GROW; organism should be EASY TO IDENTIFY (using differential media); organism should persist in the environment slightly longer than the pathogens (there is less problem with false positives than false negatives)

Question 19

fecal coliforms

Answer 19

indicator organism used to detect fecal contamination of mammals (humans); lactose-fermenting gamma proteobacteria

Question 20

fecal streptococci (enterococci)

Answer 20

indicator organism used to detect fecal contamination of animals (like ducks) but not humans; glucose-fermenting bacteria

Question 21

ratio of coliforms to streptococci

Answer 21

indicates where fecal contamination originated

Question 22

wastewater is not contaminated

Answer 22

< 400 FC/100 mL

Question 23

surface water is not contaminated

Answer 23

< 160 FC/100 mL

Question 24

drinking water is not contaminated

Answer 24

< 1 FC/100 mL

Question 25

coliforms : enterococci ≥ 4:1

Answer 25

source of fecal contamination is human

Question 26

2:1 ≥ coliforms : enterococci < 4:1

Answer 26

source of fecal contamination is a mix between human and animal

Question 27

0.7:1 ≥ coliforms : enterococci < 2:1

Answer 27

source of fecal contamination is unknown

Question 28

coliforms : enterococci < 0.7

Answer 28

source of fecal contamination is animal

Question 29

mFC plate

Answer 29

used to detect FECAL COLIFORMS… selective with BLUE ACIDS… differential with LACTOSE… colony color is BLUE… incubation temperature is 44.5 degrees Celsius

Question 30

mEA plate

Answer 30

used to detect FECAL STREPTOCOCCI (Enterococcus)… selective with SODIUM AZIDE… differential with GLUCOSE… colony color is RED… incubation temperature is 35 degrees Celsius

Question 31

bacteria can horizontally transfer genes through

Answer 31

transformation, conjugation, and transduction

Question 32

Frederic Griffith

Answer 32

first described the process of transformation using rough and smooth strains of Streptococcus pneumoniae… mixing the dead smooth strain with the live rough strain killed injected mice, but live smooth bacteria were isolated from these dead mice… indicating that something had transformed the rough strain into a smooth strain

Question 33

rough strain

Answer 33

made small compact colonies; avirulent when injected into mice

Question 34

smooth strain

Answer 34

made larger mucoid colonies; efficiently killed mice when injected into them and could be isolated from the mice postmortem (Koch’s postulates)

Question 35

heat killing the smooth strain

Answer 35

made them nontoxic

Question 36

mixing the dead smooth strain and the live rough strain

Answer 36

killed injected mice (despite non being virulent when injected individually); live smooth bacteria were isolated from the dead mice because something had transformed the rough strain into a smooth strain

Question 37

Oswald Avery

Answer 37

proved that the transforming material was DNA

Question 38

competent

Answer 38

bacteria that are capable of transporting exogenous DNA into the cell and incorporating it into their genomes (ex: streptococcus pneumoniae)