Chapter 5

Question 1

Growth

Answer 1

increase in size of an individual, or the increase in number of cells

Question 2

population size can be measured using: (4)

Answer 2

1. total count of cells (dead of alive)
2. viable count of cells (only culturable cells)
3. turbidometric means (optical density via a spectrophotometer)
4. cell components (dry weight, protein content, etc.)

Question 3

Generation time

Answer 3

time for microbial cells to double in number

Question 4

Septum

Answer 4

partitioning between daughter cells, pinches off to form 2 equal daughter cells

Question 5

Budding division

Answer 5

unequal cell growth, totally new daughter cell
- simple, from hyphae, stalks, appendages

Question 6

biofilms

Answer 6

attached polysaccharide matrix containing embedded bacteria
- sessile growth on surfaces
- planktonic cells attach -> production of sticky matrix

Question 7

Microbial mats

Answer 7

multilayered sheets w different organisms in each layer
- hot springs, intertidal regions

Question 8

Biofilms prevent:

Answer 8

• harmful chemicals (antibiotics) from penetrating
• protists from grazing
• washing away of cells

Question 9

Exponential growth

Answer 9

growth of microbial populations where cell numbers double within a specific time

Question 10

Generation time

Answer 10

(g)
- g = t/n
- duration of exponential growth / number of doublings (generations) during that duration

Question 11

Growth rate constant

Answer 11

slope of the line, represents rate of increase in growth rate during natural logarithmic growth

Question 12

growth equation

Answer 12

final # cells = initial # cells x generations elapsed
k = log10Nt - log10N0 / rise x t

Question 13

Viable count

Answer 13

measures the cells in the culture that are capable of reproducing

Question 14

optical density (turbidity)

Answer 14

a quantitative measure of light scattering by a liquid culture, increases with the increase in cell numbers

Question 15

batch culture

Answer 15

a closed system, microbial culture of fixed volume

Question 16

four phases of bacterial growth curve:

Answer 16

lag phase, exponential phase, stationary phase, death phase

Question 17

Diauxic growth

Answer 17

Diphasic growth, catabolite repression
- 2 exponential growth phases
- 2 lag phases

Question 18

continuous culture

Answer 18

open system microbial culture of fixed volume
- nutrients in, wastes out
can maintain exponential growth phase for weeks/months
- growth rate controlled by dilution rate

Question 19

Chemostat

Answer 19

common type of continuous culture device
- nutrients in, wastes out

Question 20

Dilution rate

Answer 20

F/V
- Flow rate of added medium and removing spent medium / culture volume

Question 21

Steady state

Answer 21

cell density and substrate concentration do not change over time

Question 22

culture media

Answer 22

nutrient solutions used to grow microbes in the laboratory

Question 23

defined media

Answer 23

exact chemical composition knwon

Question 24

complex media

Answer 24

composed of digests of microbial, animal, or plant products (yeast/meat extracts)

Question 25

enriched media

Answer 25

contain complex media plus highly nutritious materials, used to culture fastidious (nutritionally demanding) microbes

Question 26

selective media

Answer 26

contain compounds that selectively inhibit growth of some microbes but not others

Question 27

differential media

Answer 27

contain an indicator, usually a dye, that detects particular metabolic reactions during growth