Chapter 4 (Book) Microbial Growth

Question 1

planktonic cells

Answer 1

free-living organisms that grow and multiply on their own

Question 2

binary fission

Answer 2

one parental cell splits into two equal daughter cells

Question 3

growth rate

Answer 3

rate of increase in cell numbers/biomass is proportional to population size at a given time

exponential growth

Question 4

starting with any # of organisms (No), what is the number of organisms after n generations

Answer 4

No x 2^n

Question 5

generation time

Answer 5

the constant interval at which bacteria divide in an environment with unlimited resources

Question 6

doubling time

Answer 6

generation time for cells in culture

Question 7

the length of the generation time depends on what

Answer 7

bacterial species

medium

temperature

pH

Question 8

growth constant rate (k)

Answer 8

number of generations per unit time

Question 9

why doesn’t exponential growth last forever

Answer 9

nutrient consumption and toxic by-products slow growth rate

Question 10

batch bulture

Answer 10

no fresh medium is added in incubation

nutrients decline and waste products accumulate during growth

Question 11

4 stages of growth

Answer 11

lag phase

log phase

stationary phase

death phase

Question 12

lag phase

Answer 12

phase when cells don’t divide

cells prepare machinery for growth

Question 13

log phase

Answer 13

exponential growth occurs at maximum rate

Question 14

stationary phase

Answer 14

rate of cell division equals rate of cell death

shut down growth machinery and turn on stress responses

Question 15

death phase

Answer 15

logarithmic death

number of cells that die is proportional to number of cells that existed in the beginning of the time period

Question 16

continuous culture

Answer 16

fresh medium constantly added, and old constantly removed

allows log phase for a long time

Question 17

chemostat

Answer 17

continuous culture system where there is a limited amount of an essential nutrient

increasing flow rate increases amount of nutrient available

Question 18

biofilm

Answer 18

specialized surface-attached collaborative communities of bacteria

Question 19

when do biofilms form

Answer 19

when nutrients are plentiful

Question 20

what happens when nutrients become scarce, biofilm

Answer 20

individuals detach from the community to forage for new sources of nutrients

Question 21

signals for formation of biofilms

Answer 21

pH

temperature

oxygen levels

Question 22

formation of a biofilm

Answer 22

signal causes planktonic cells to attach to a surface via pilli or adhesion structures

more cells attach and they spread out

the community talks to each other by sending chemical signals

Question 23

bacteria faced with environmental stress undergo…

Answer 23

complex molecular reprogramming

Question 24

endospore

Answer 24

gram-pos mostly

metabolically inactive spore that is resistant to heat and desiccation

formed b/c of starvation

Question 25

SASP

Answer 25

small acid-soluble proteins

found in spores to protect DNA

Question 26

germination

Answer 26

genetic response wakes up a spore to release a normal vegetative cell

Question 27

cyanobacteria differentiate into nitrogen-fixing ________

Answer 27

heterocysts - special cells that function in nitrogen fixation

every 10th cell becomes one

Question 28

starvation can induce differentiation into ________ bodies

Answer 28

fruiting

gram-neg mostly… aggregation of 100,000 cells

use a gliding motility (pilus) to travel

Question 29

actinomycetes form _____ and ______

Answer 29

mycelia, sporangia – like fungi

germ tube emerges from a germinating spore

forms branches that grow along the surface of a food source