Micro 1- microbial growth

Question 1

list 4 types of reproduction

Answer 1

1. binary fission
2. budding
3. sexual reproduction
4. fragmentation

Question 2

binary fission

Answer 2

DNA is copied and cell divides into two equal cells

• most common in bacteria
• asexual

Question 3

budding

Answer 3

small initial growth that enlarges and then separates

• yeast most common
• asexual

Question 4

sexual reproduction

Answer 4

• requires two opposite mating strains
• generates diversity
• individual produced is genetically different from parents
• eukaryotic organisms (fungi, protozoa)

Question 5

fragmentation

Answer 5

filamentous bacteria break off and initiate growth of new cells

Question 6

generation time

Answer 6

time required for a cell to divide and its population to double (20 minutes to 24 hours)

Question 7

binary fission and generation time

Answer 7

binary fission doubles the number of cells each generation
total number of cells = 2^(number of generations)
-growth curves are represented logarithmically

Question 8

4 phases of growth

Answer 8

1. lag phase
2. log phase
3. stationary phase
4. death phase

Question 9

lag phase

Answer 9

intense activity preparing for population growth but no increase in population
-no cell division, prep for growth

Question 10

log phase

Answer 10

logarithmic or exponential increase in population

note very rapid growth makes bacterial cells more permeable

Question 11

stationary phase

Answer 11

period of equilibrium, microbial deaths balance production of new cells

Question 12

death phase

Answer 12

population is decreasing at a logarithmic rate

Question 13

in what phase is bacteria most susceptible to chemical agents

Answer 13

log (exponential) phase

• because cell wall is not effective barrier at this stage (more permeable and allows for passage of molecules)
• antibiotics take advantage of this

Question 14

physical requirements for growth (3)

Answer 14

1. temperature
2. pH
3. osmotic pressure

Question 15

chemical requirements (5)

Answer 15

1. carbon
2. nitrogen, sulfur, and phosphorous
3. trace elements
4. organic growth factors
5. oxygen

Question 16

temperature requirements

psychrophiles, mesophiles, thermophiles

Answer 16

psychophiles- cold loving

psychrotrophs (room temp loving- food spoiling)

Question 17

pH requirements

Answer 17

most bacteria grow between 6.5 and 7.5 pH
(mods and yeasts grow between 5 and 6 pH)
most pathogens are neutrophiles- requiring neutral conditions

Question 18

osmotic pressure requirements

Answer 18

hypertonic environments (higher in solutes than inside the cell) cause plasmolysis due to high osmotic pressure

Question 19

extreme/ obligate halophiles

Answer 19

require high osmotic pressure (high salt)

Question 20

facultative halophiles

Answer 20

tolerate high osmotic pressure

doesn’t need it to survive but can live through it

Question 21

carbon requirements

Answer 21

• structural backbone or organic molecules
• chemoheterotrophs use organic molecules as energy
• autotrophs use CO2 (some bacteria, protozoa, and algae)

Question 22

nitrogen requirements

Answer 22

component of proteins, DNA, and ATP

-most bacteria decompose protein materia for the nitrogen source

Question 23

sulfur and phosphorus requirements

Answer 23

sulfur is used in animo acids, thiamine, and biotin

phosphorus is used in DNA, RNS, and ATP

Question 24

trace element requirements

Answer 24

• inorganic elements required in small amounts
• used as enzyme cofactors
• include iron, copper, molybdenum, and zinc

Question 25

organic growth factor requirements

Answer 25

• organic compounds obtained from the environment

- vitamins, amino acids, purines, and pyrimidines

Question 26

obligate aerobes

Answer 26

require oxygen

Question 27

facultative aerobes

Answer 27

grow via fermentation or anaerobic respiration when oxygen is not available

Question 28

obligate anaerobes

Answer 28

unable to use oxygen or are harmed by it

Question 29

aerotolerant anaerobes

Answer 29

tolerate but cannot use oxygen

Question 30

microaerophiles

Answer 30

require oxygen concentration lower than air