Bacterial Growth

Question 1

What is bacterial growth ?

Answer 1

bacterial cells build up protoplasm and double in size
- once doubled each of its parts the cell divides into 2 daughter cells

Question 2

What is binary fission ?

Answer 2

when a cell divides into 2 daughter cells
- a way that bacteria reproduce

Question 3

What needs to duplicate in binary fission before the cell can divide ?

Answer 3

prokaryotic chromosome

Question 4

How do we measure bacterial growth ?

Answer 4

by the increase of number of bacterial cells

Question 5

What are the different methods of measuring bacterial growth ?

Answer 5

• calibration
• pour plate/spread plate method

Question 6

How does the pour plate method work ?

Answer 6

1. inoculate empty plate
2. add melted nutrient agar
3. swirl to mix
4. colonies grow in and on solidified medium
   - use either 1.0 or 0.1 ml

Question 7

How does a spread plate method work ?

Answer 7

1. inoculate plate containing solid medium
2. spread inoculum over surface evenly
3. colonies grow only on the surface of the medium
   - liquid can’t be easily soaking up on the solid medium
   - can only use about .1 ml

Question 8

In what cases would we use serial dilution ?

Answer 8

when working with very contaminated samples
- want isolated colonies

Question 9

What is a dilutant ?

Answer 9

liquid that is sterile that has no bacteria in it

Question 10

Why do we want isolated colonies ?

Answer 10

so they are easily identifiable and can see how bacteria are growing on the plate
- more qualitative then quantitative
- you can tell if you have a pure or mixed culture
- want to see individual/isolated colonies in serial dilutions

Question 11

Why would someone do a streak plate ?

Answer 11

lets you isolate a single type of bacteria
- you spread out the parent bacteria into 4 quadrants so that the bacteria gradually become more isolated in each quadrant
- in 4th quadrant you should have isolated colonies

Question 12

Why is isolating bacteria important ?

Answer 12

want to see how the bacteria grow on the plate and to identify them

Question 13

What does the minimum temp of a bacteria mean ?

Answer 13

the lowest temp that permits growth

Question 14

What does the maximum temp of a bacteria mean ?

Answer 14

highest temp that permits growth

Question 15

What does the optimum temp of a bacteria mean ?

Answer 15

range of temp that promotes the highest growth rate

Question 16

Is the min, max, and optimum temp of each bacteria the same ?

Answer 16

no
- bacteria grow over a range of temps

Question 17

What are the 4 temp groups that bacteria grow in ?

Answer 17

psychrophiles, mesophiles, thermophiles, extreme thermophiles

Question 18

What are psychrophiles ?

Answer 18

• optimum between 5-20 C
• like cooler temps like snow fields, polar ice or ocean depths
• Ex.) flavobacterium spp

Question 19

What are mesophiles ?

Answer 19

• optimum between 20-50 C
• the temp that our human pathogens and majority of bacteria like

Question 20

What are thermophiles ?

Answer 20

• optimum between 50-80 C
• like it hot
• Ex.) bacteria in habitats exposed to sun, or in hot springs; bacillus stearothermophillus

Question 21

What are extreme thermophiles ?

Answer 21

• optimum between 80 C and above
• like it very hot
• ex.) can find in soil and water associated with volcanic activity

Question 22

Describe Obligate (strict) aerobes

Answer 22

• must have O2 to grow
• use respiration to get energy
• ex.) pseodomonas aeruginosa

Question 23

Describe Obligate (strict) anaerobes

Answer 23

• cannot grow in the presence of O2
• use fermentation to get energy
• ex.) bacteroides fragilis

Question 24

Describe Facultative anaerobes

Answer 24

• prefer to grow in O2 but can grow without O2
• uses both fermentation and respiration
• happens optionally in response to circumstances rather then by nature

Question 25

Describe Microaerophilic organisms

Answer 25

• need O2 in small amounts yet will die without O2
• ex.) helicobacter pylori, and Neisseria gonorrhoeae

Question 26

Describe Aerotolerant organism

Answer 26

• grows with or without O2 (O2 has no impact on growth)
• growth occurs evenly throughout culture tube
• ex.) streptococci species

Question 27

What type of bacteria doesn’t have a detoxifying pathway ?

Answer 27

anaerobic bacteria
- since they can’t detoxify then bacteria will die

Question 28

What type of bacteria has a detoxifying pathway ?

Answer 28

aerobic or facultative bacteria
- since they can detoxify they can turn that into nontoxic products like H2O and O2

Question 29

What nutrients are required for bacterial growth ?

Answer 29

need source of Carbon from catabolized organic molecules like
- proteins, carbs, fatty acids, amino acids, etc

Question 30

Where does the energy come from for bacterial growth ?

Answer 30

from “redox” (reduction and oxidation) reactions
- primary energy source is glucose metabolism

Question 31

What are other sources required for bacteria growth ?

Answer 31

vitamins, minerals, and water
- need hydrogen ions which they get from the water

Question 32

What are the phases of the bacterial growth curve in order ?

Answer 32

• lag phase
• exponential/log phase
• stationary phase
• death phase

Question 33

What occurs in the lag phase ?

Answer 33

bacteria is adjusting to new environment before reproduction and needs time to adapt
- cells not reproducing at max rate

Question 34

What occurs in the exponential/log phase ?

Answer 34

start to divide rapidly, going through binary fission very quickly
- reproduction at max rate
- growth continues as long as nutrients and space is sufficient and environment is favorable

Question 35

What occurs in the stationary phase ?

Answer 35

bacteria is going to stop growing so rapidly and the curve will flatten out
- decline in growth
- increase in death

Question 36

What occurs in the death phase ?

Answer 36

population starts to go down rapidly
- gone through all their resources and have no room to grow anymore
- toxins might be built up in environment

Question 37

What happens in a closed system in relation to bacterial growth curve ?

Answer 37

• nutrients and space are limited
• the waste products stay in there and can toxify the environment and cause harm to the bacteria since there is no mechanism to remove it