ch 6

Question 1

How does pH effect microbial growth in cultures

Answer 1

most grow between pH of 6.5-7.5

Question 2

How does temp effect microbial growth in cultures

Answer 2

there is a mininmum, optimum, and maximum growth temp

Question 3

how does osmotic pressure effect microbial growth in cultures

Answer 3

hypertonic enviroment- cause plasmolysis

Question 4

psychrophilies

Answer 4

extreme cold growth

Question 5

microbial growth

Answer 5

increase in number of cells, not cell size- colonies

Question 6

mesophile growth temp

Answer 6

between 10-50 C, medium temp

Question 7

thermophiles growth temp

Answer 7

between 40-70 C

Question 8

acidophiles

Answer 8

grow in acidic environment

Question 9

plasmolysis

Answer 9

caused by hypertonic environment or an increase in salt or sugar

Question 10

extreme or obligate halophiles

Answer 10

require high osmotic pressure to grow

Question 11

obligate aerobes

Answer 11

require oxygen to grow- org at top of tube

Question 12

faculative anaerobes

Answer 12

have both aerobic and anaerobic growth but greater growth w oxygen- mainly at top of tube w some throughout

Question 13

obligate anaerobes

Answer 13

only anaerobic growth, ceases in presence of oxygen- all at bottom of tube

Question 14

microaerophiles

Answer 14

only aerobic growth, oxygen required at low concentration- grouped in center of the tube

Question 15

aerotolerant anaerobes

Answer 15

only anaerobic growth, but continues in the presence of oxygen- even growth throughout tube

Question 16

what nutrients effect microbial growth in a culture

Answer 16

carbon, nitrogen, sulfer, phosphorus, and trace elements

Question 17

psychotrophs

Answer 17

main cause of food spoilage

Question 18

chemically defined media

Answer 18

exact composition is known

Question 19

complex media

Answer 19

extracts and digests of yeasts, meat, or plants

Question 20

selective media

Answer 20

supress unwanted microbes nd encourage desired microbes

Question 21

differential media

Answer 21

make it easy to distinguish colonies of different microbes

Question 22

enrichment media

Answer 22

encourages growth of desired microbes

Question 23

agar

Answer 23

complex polysaccharide used as solidifying agent, generlly not metabolizd by microbes, liquid at 100C and solid at 40C

Question 24

broth

Answer 24

liquid form of agar

Question 25

biosafety level 1

Answer 25

no special precautions

Question 26

biosafety level 2

Answer 26

lab coat, gloves, eye protection

Question 27

biosafety level 3

Answer 27

biosafety cabinets to prevent airborne transmission

Question 28

biosafety level 4

Answer 28

sealed negative pressure

Question 29

formation of biofilms

Answer 29

form slime or hydrogels that share nutrients and shelter from harmful factors, can migrate and use quorum sensing (bacteria attracted by chem)

Question 30

microoganism preservation

Answer 30

deep freeze- -(50-90C)

lyophilization

Question 31

lyophilization

Answer 31

freeze drying and dehydrated in a vacuum

Question 32

binary fission- microbial growth

Answer 32

1. cell elongates and DNA replicated
2. cell wall and plasma membrane constrict
3. crosswall forms
4. cell seperates into daughter cells

Question 33

generation

Answer 33

each time a colony doubles in size

Question 34

generation phases

Answer 34

1. lag- intense act prep for growth but no increase in pop
2. log-exponential increase in pop
3. stationary-period of equillibrium
4. death- pop decrease at exponential rate

Question 35

refridgeration

Answer 35

may allow for slow growth of spoilage bacteria but does not kill microbes
no significant growth below freezing

Question 36

colony

Answer 36

a population of cells arising from a single cell, spore, or group of attached cells

Question 37

CFU

Answer 37

colony forming unit

Question 38

turbidity

Answer 38

the cloudiness of a suspension