Microbial Growth

Question 1

What are cultures?

Answer 1

Microbes that are continuously growing and multiplying.

Question 2

What are inoculum?

Answer 2

Microbes that are introduced into a culture

Question 3

What is inoculation

Answer 3

The introduction of microbes into a culture

Question 4

What is batch culture

Answer 4

Microbes in liquid media where once started, nutrients are not added further

Question 5

What is the limiting components of batch culture

Answer 5

The limiting component is the nutrients

Question 6

What is batch culture used for?

Answer 6

They are used to analyze how microbes grow

Question 7

What is a continuous culture

Answer 7

These are microbes that grow in open system, where nutrients are continuously added and waste are continuously removed.

Question 8

What does agar do?

Answer 8

Agar is a solidifying agent that is used to turn liquid broth into solid media

Question 9

What is an agar

Answer 9

Polysaccharide derived from marine algae that can’t be degraded by bacteria

Question 10

What is cultural medium

Answer 10

These are nutrients prepared for microbial growth and can be in liquid(broth) or solid( with agar)

Question 11

Why are cultural medium important?

Answer 11

It allows us to grow pure bacterial culture in the lab

Question 12

Why must the media be sterile prior to inoculation

Answer 12

So that only the cells that you want to reproduce are being grown.

Question 13

What does it mean to be sterile

Answer 13

No living microbe is present

Question 14

What can kind of medium is there

Answer 14

There are chemical defined and chemically undefined medium

Question 15

What does chemically undefined media mean?

Answer 15

It means that the medium contains unknown components

Question 16

What does chemically defined media mean?

Answer 16

It means that all of the media components are known

Question 17

What is selective media used for?

Answer 17

It is used to suppress the growth of unwanted organism while promoting growth of desired organism

Question 18

What is differential media used for?

Answer 18

It is used to distinguish different types of bacteria, although all types of bacteria can grow colonies of certain bacteria look different

Question 19

What is an selective and differential media

Answer 19

MacConkey agar for example is both selective and differential media because it inhibits the growth of non-intestinal bacteria while promoting the growth of intestinal bacteria. It also differential media because bacteria that ferment lactose appear pink, while non-lactose fermenter like most intestinal pathogens appear white on the ph indicator.

Question 20

What is bacterial growth

Answer 20

Increase in bacterial cell number and not an increase in bacterial cell size

Question 21

How does bacteria reproduce

Answer 21

They reproduce through binary fission

Question 22

How does binary fission occur

Answer 22

Bacteria elongates and duplicate its chromosomes then cross wall forms between the 2 chromosomes.after that 2 cells separate and form new identical daughter cell

Question 23

What is generation time

Answer 23

The time it takes for a bacterial population to double in size

Question 24

How is the bacterial growth carve graphed

Answer 24

It is graphed using the log of the cell number

Question 25

1st phases in the bacterial growth carve

Answer 25

-the lag phase is a period of adaption, the cells are adapting to the new media and preparing for growth

Question 26

How can bacteria be counted

Answer 26

They can be counted through direct and viable count

Question 27

What is direct count

Answer 27

Cells are counted using light microscope

Question 28

What is viable count

Answer 28

Only live cells are counted

Question 29

What is the process for viable count

Answer 29

A liquid cultured is diluted, the dilution are plated into agar medium, and the plates are incubated until the colonies grow. Each cell from the original dilution develop into a single colony, the number of colonies are counted and used to determine the number of bacterial that were represent in the original sample. The counts are expressed as colony forming unit per mL(cfu/mL), the assumption is that 1cfu = 1 bacterial cell

Question 30

2 phase in bacterial growth curve

Answer 30

• exponential phase is a period of maximal reproduction, this phase is used to calculate growth rate

Question 31

3rd phase in the bacterial growth curve

Answer 31

• stationary phase, cells have reached max population density, nutrients have been depleted, growth rate equals death rate.

Question 32

4th phase in the bacterial growth curve

Answer 32

• death phase, all nutrients are exhausted, toxic waste has accumulated and death rate exceeds growth rate.