MMB03 Microbial Growth

Question 1

How do bacteria divide

Answer 1

Binary fission

Question 2

What are the downsides to using microscopy or viable counts to measure microbial growth

Answer 2

It’s very laboratory intensive
Very time consuming

Question 3

What is Turbidity

Answer 3

Turbidity is the measure of optical density of a liquid (cloudier liquids are more Turbid)

Question 4

How can we use turbidity in microbial growth

Answer 4

The increasing turbidity caused by the increase in microorganisms as they multiply can be measured with a spectrometer and used to quickly and easily make growth curve

Question 5

What are the phases of a bacterial growth curve

Answer 5

Lag phase
Exponential phase
Stationary phase
Death phase

Question 6

What happens during the lag phase

Answer 6

Microbes are adapting to the new environment. They need time to produce the necessary biochemical components required for growth.

If a culture is transferred to a new medium with the same conditions then there will be no lag phase as the microorganisms are already adapted

Question 7

What happens during the exponential phase

Answer 7

Bacteria are growing and multiply exponentially through logarithmic growth.

Question 8

What happens during the stationary phase

Answer 8

The rate of cells multiplying is equal to the rate of cells dying resulting in no net growth.
This occurs when an essential nutrient for cell growth is depleted
Or when a biproduct of growth accumulates and inhibits cell growth
Many other cell functions like energy metabolism and biosynthesis still take place

Question 9

What happens in the death phase

Answer 9

Cells start dying, in some cases the cells will undergo lysis.

Cell death is also exponential, but at a much slower rate than cell growth

Question 10

What is a psychrophile

Answer 10

A microorganism that grows most optimally in cold conditions between -5-10 C

Question 11

What is a mesophile

Answer 11

A microorganism that grows most optimally in warm conditions between 15-45 C

Question 12

What is a thermophile

Answer 12

A microorganism that grows most optimally in hot conditions between 45-70 C

Question 13

What is a hyperthermophile

Answer 13

A microorganisms that grows most optimally in very hot conditions over 70 C

Question 14

Why are thermophiles and hyperthermophiles useful in industry?

Answer 14

There enzymes work at very high temperatures without being denatured. High temperatures allow for many industrial processes to occur more efficiently

Question 15

What are acidophiles

Answer 15

Microorganisms that grow best below pH 5.5

Question 16

What are alkaliphiles

Answer 16

Microorganisms that grow best above pH8

Question 17

What is a nonhalophile

Answer 17

Microorganisms that do not grow very well in salty conditions

Question 18

What is a halotolerant

Answer 18

Microorganisms that grow best in mildly salty conditions below 10%

Question 19

What is a halophile

Answer 19

Microoganisms that grow best in salty conditions

Question 20

What are the different categories of oxygen requirements

Answer 20

Obligate aerobes
Facultative anaerobes
Obligate anaerobes
Aerotolerant anaerobes
Microaerophiles

Question 21

What is an obligate aerobe

Answer 21

Organisms that can only grow aerobically in the presence of oxygen. Can remove toxic forms of oxygen

Question 22

What is a facultative anaerobe

Answer 22

Can grow both aerobically and anaerobically, usually prefer aerobic growth. Can remove toxic forms of oxygen

Question 23

What is an obligate anaerobe

Answer 23

Can only grow anaerobically without the presence of oxygen. Can not remove toxic forms of oxygen so will die in aerobic conditions

Question 24

What are aetotolerant anaerobes

Answer 24

Can only grow anaerobically. It can however remove toxic forms of oxygen so can survive in aerobic conditions

Question 25

Microaerophiles

Answer 25

Can only grow aerobically in areas with a low oxygen concentration. Higher levels of oxygen are lethal and it can not grow

Question 26

Why is oxygen toxic to some microorganisms

Answer 26

All organisms can reduce oxygen, however this produces toxic biproducts like hydrogen peroxide and oxygen radicals.
Aerobic or aerotolerant microorganisms can remove or neutralise these toxic forms of oxygen
However obligate anaerobes can not and will die

Question 27

What anabolic mean

Answer 27

Processes that build up substances like the biosynthesis of macromolecules

Question 28

What does catabolic mean

Answer 28

Processes that lead to energy conservation, usually through breaking down bonds in molecules e.g. the breakdown of ATP into ADP

Question 29

What is a defined culture media

Answer 29

Prepared by adding highly purified chemicals to distilled water

Question 30

What is a complex culture media

Answer 30

A highly nutritious media where the exact composition is unknown making it easier to prepare than a defined media.

Used when high growth is required but the knowledge of the exact composition is not essential

Question 31

What is general purpose culture media

Answer 31

A media that can culture a wide range of different bacteria

Question 32

What is a selective culture media

Answer 32

A media that contains compounds that inhibit the growth of some microorganisms but not others

Question 33

What is a differential culture medium

Answer 33

A medium where an indicator is added that shows whether a chemical reaction has taken place