Chapter 12

Question 1

how do microbiologists define growth

Answer 1

• an increase in cell numbers
• mother cell doubles in size and duplicates cell contents

Question 2

budding

Answer 2

small new cell develops from the surface of an existing one

Question 3

which microbes divide via budding

Answer 3

yeast

Question 4

binary fission

Answer 4

cell duplicate its content and divides into two cells (septum)

Question 5

which microbes divide via fission

Answer 5

bacteria

Question 6

what are the four phases of bacterial growth curve

Answer 6

• lag phase
• log phase
• stationary phase
• death phase

Question 7

lag phase

Answer 7

• organisms are metabolically active but not increasing significantly in numbers
• increases in size getting ready to divide
• one hour to several days depending on organism

Question 8

log phase

Answer 8

• organisms adapted to environment
• growth occurs exponentially
• dividing at their most rapid rate
• between 20 min to 20 hours

Question 9

stationary phase

Answer 9

• horizontal line
• cell division decreases due to limitation on nutrients to the point that new cells are produced at the same rate as old cells die
• cell division equals death

Question 10

death phase

Answer 10

• the medium becomes less favorable
• less nutrients, less space and more waste
• cells die at a logarithmic rate
• some might produce spores

Question 11

quorum sensing

Answer 11

communication between bacteria through signals

Question 12

biofilm

Answer 12

• microbe that forms layers and lives in communities
• teeth plaque
• slimy layer on top of rocks in a stream
• outside or inside of catheters

Question 13

sociomicrobiology

Answer 13

how microbes interact in groups

Question 14

what are colony forming units (CFU)

Answer 14

when a single living bacterium is deposited in an agar palate, it will divide to form colonies

Question 15

why are colonies an underestimation

Answer 15

• not every cell will survive in the plate
• two organisms might end up too close to each other and look like one colony
• some nutritional requirements

Question 16

which two ways can you obtain colony forming units

Answer 16

• streak for isolation
• dilution plates

Question 17

what are the differences between streaking and diluting

Answer 17

streaking obtains single colonies, diluting determines how many organisms are in a specific amount of sample

Question 18

hemocytometer

Answer 18

• uses microscope
• counts cell

Question 19

what are the three types of media

Answer 19

• selective media
• differential media
• enrichment media

Question 20

selective media

Answer 20

• encourages the growth of some organisms but suppresses growth of others
• MAC, MSA

Question 21

differential media

Answer 21

• has a chemical that causes an observable change in the medium when a biochemical reaction occurs
• MAC, MSA

Question 22

enrichment media

Answer 22

• special nutrients
• blood agar
• chocolate agar

Question 23

how do we provide the nutritional influences needed for growth

Answer 23

• availability of carbon
• availability of nitrogen
• availability of sulfur
• availability of phosphorus
• availability or trace elements
• availability of vitamins

Question 24

effects of temperature on growth

Answer 24

• most enzymes have an optimum temperature that is near the organisms temperature of 37
• they also have a range of temperature - denature
• organisms that infect humans usually have similar optimal temperature

Question 25

effect of pH on growth

Answer 25

- most enzymes have an optimum pH of 7 - they also have a range of pH at which it can survive

Question 26

acidophile

Answer 26

0.1 to 5.4

Question 27

neutrophiles

Answer 27

5.4 to 8.0

Question 28

alkaphiles

Answer 28

8.0 to 11

Question 29

psychophile

Answer 29

15

Question 30

mesophile

Answer 30

37

Question 31

typical thermophile

Answer 31

62

Question 32

extreme thermophile

Answer 32

87