Microbial Growth and Nutrition

Question 1

How do we define bacterial growth?

Answer 1

Orderly increase in numbers

Question 2

What are the B,C,D periods of binary fission?

Answer 2

B: Cell increases in mass and size

C: DNA replicates and the 2 strands separate

D: Synthesis of a septum forms 2 identical cells

Question 3

Do all cells replicate at the same rate?

Answer 3

No, depending on the species they all have an optimal replication rate

Question 4

What is the regeneration time of E. coli?

Answer 4

15 mins

Question 5

How do bacterial and archaea cells reproduce?

Answer 5

Asexually

-generation time is the interval between successive binary fissions

Question 6

What are the 4 phases of the microbial growth process?

Answer 6

1. Lag phase
2. Logarithmic phase
3. Stationary phase
4. Decline phase

Question 7

What happens during the lag phase?

Answer 7

No cell division occurs while bacteria adapt to their new environment

Question 8

What happens during the logarithmic phase?

Answer 8

Exponential growth of the population occurs, human disease symptoms usually develop

Question 9

What happens during the stationary phase?

Answer 9

When reproductive and death rates are equalized

Question 10

What happens in the decline phase?

Answer 10

Accumulation of waste products and decline of resources causes the population to die

Question 11

What state can bacteria exist in and why?

Answer 11

Metabolically inactive states which can be a response to potential or actual environmental change

Question 12

Why are endospores important for cell growth?

Answer 12

They are a response to nutrient limitations

-have thick walls to survive harsh conditions

Question 13

What is a psychophile?

Answer 13

Can grown between -10 and 20

Question 14

What is a psychotrops?

Answer 14

Can grow between 0-30

Question 15

What is a mesotroph?

Answer 15

Can grow between 10-58

Question 16

What is a thermophile?

Answer 16

Can grow between 40-73

Question 17

What is a hyperthrermophile?

Answer 17

Can grow between 76- 110

Question 18

What are obligate aerobes?

Answer 18

They require O2 to grow

Question 19

What is a microaerophile?

Answer 19

Live in low O2 environments

Question 20

What are facultative anaerobes?

Answer 20

Grow either with O2 or in reduced O2 environments

Question 21

What is a capnophilic bacteria (microaerophils)?

Answer 21

Require an atmosphere low in O2 and rich in CO2

Question 22

At what pH do majority of species grow at?

Answer 22

~7.0

Question 23

What are barophiles?

Answer 23

Withstand really high hydrostatic pressure

Question 24

What is media?

Answer 24

What ever we make to grow bacteria on

-most require special growth factors or nutrients

Question 25

What is agar?

Answer 25

Complex polysaccharide from cell walls of red algae

Question 26

Why do we use agar as a medium?

Answer 26

- Most microbes can not digest it - Dissolves in water at 100 - Solidifies below 40 - can culture hyperthermophiles

Question 27

In a test tube with agar, why do you slant it?

Answer 27

Gives more area for you to put bacteria on the grow

Question 28

What is nutrient broth?

Answer 28

Powdered beef extract - AA mix from digested proteins - 1.5% agar if you need to solidify

Question 29

What us a defined media?

Answer 29

Synthetic media for something specific you want to grow | -exact chemical composition is known

Question 30

What are culture media used for?

Answer 30

growing microbes and to measure their growth

Question 31

What are the 2 basic types of culture media?

Answer 31

Complex medium is chemically undefined or complex medium such as nutrient broth or nutrient agar

Question 32

What is a complex media | ?

Answer 32

Contains nutrients released from partial hydrolysis of yeast, beef, soy or proteins - chemical comp is not known - can support wide variety of microbes

Question 33

What does a a selective medium contain?

Answer 33

Ingredients to inhibit growth of certain species and allow the broth of others

Question 34

What are differential mediums?

Answer 34

Differential medium contains specific chemicals to indicate species that possess or lack a biochemical process

Question 35

What are fastidious organisms?

Answer 35

Require an enriched medium containing specific nutrients

Question 36

What is a selective media?

Answer 36

Contains substances that either favour or inhibit certain microbes from growing

Question 37

How do you measure population?

Answer 37

Measurements are made using pure cultures

Question 38

What is a pure culture?

Answer 38

Population consisting of only one species of prokaryotes

Question 39

What are the 2 forms of isolation?

Answer 39

Pour-plate: allows separation of species through dilution of sample Streak-plate: Spreads individual cells to form discrete colonies of species

Question 40

How do you measure population growth?

Answer 40

Turbidity: cloudiness with spectrophotometer Microscopic count: Count bacteria in the squares Visually: Counting them