Ex. 16 Temperature

Question 1

do microbes have homeostatic mechanisms

Answer 1

they do not have mechanisms to maintain internal eqlbm, directly affected by changes in their environment

Question 2

what happens at high temp

Answer 2

membrane melt, bacterial enzyme activity will increase until a point where they are denatured

Question 3

what happens at low temp

Answer 3

inactivation of enzymes, cellular metabolism diminishes, membrane solidifies. at 0C biochemical runs cease in most cell

Question 4

what can lead to a narrow range of temp

Answer 4

stressed environment such as acidic conditions

Question 5

psychrophiles

Answer 5

can grow at 0C. optimal 10-15C. found in ocean where temp remains cold with little fluctuation

Question 6

psychrotrophs

Answer 6

adapted to habitats from 0-30C. optimal is 20-30C. cause of refrigerated food spoilage

Question 7

mesophiles

Answer 7

20-45C. majority of bacteria including most human pathogens. can grow at human body temp 37C

Question 8

thermophiles

Answer 8

above 55C. in composing organic material and hot springs

Question 9

extreme thermophiles

Answer 9

thrive at temps above 85C

Question 10

thermodurics

Answer 10

organism that survive 85C but do not multiple. e.g. endosperm formers

Question 11

examples of dry heat

Answer 11

hot air ovens, bacticinerator. denatures enzymes, dehydrate microbes and kills oxidation effects

Question 12

examples of moist heat

Answer 12

boiling, pasteurization

Question 13

disadvantage of dry heat

Answer 13

heat of hot air is not readily transferred to a cooler body such as microbial cell, so treatments for sterilization takes place over long periods

Question 14

how long to dry heat in an oven

Answer 14

170C for 2 hours

Question 15

method of pasteurization

Answer 15

temp at 63C for 30 mins or 72C for 15 sec (flash pasteurization). kills pathogenic or causes spoilage bacteria

Question 16

boiling

Answer 16

100C for 10 mins kills vegetative but endospores are inactivated

Question 17

autoclaving

Answer 17

most effective moist heat sterilization, use of steam under pressure. increased pressure raises bp of water produces steam with higher temp. 121C for 15mins

Question 18

thermal death time

Answer 18

length of time required to kill all bacteria and endospores in a liquid culture at give temp

Question 19

thermal death point

Answer 19

temp required to kill all bacteria and endospores in a liquid culture in 10 mins

Question 20

Serratia marcescens produces a

Answer 20

non water soluble red pigment called prodigiosin

Question 21

prodigiosin

Answer 21

toxic to certain micro-organism, acts as an antibiotic enabling Serratia to compete more effectively w/others in its normal environment

Question 22

Serratia marcescens thrive on

Answer 22

dust and moisture