Microbiology 1, 2 and 3

Question 1

Define microbe

Answer 1

A living organism that can only be seen with a microscope

Question 2

Where are microbes mostly found?

Answer 2

Microbes are concentrated in the large intestine

They are not found in human tissue

Question 3

How many cells are microbes normally formed from?

Answer 3

microbes are normally unicellular - 1 cell

Question 4

What is meant by a biofilm?

Answer 4

Microbes attach irreversibly to a surface and grow on it

Question 5

List the different types of microbe

Answer 5

Algae
Archae
Bacteria
Fungi
Protozoa
Virus

Question 6

Describe the characteristics of bacteria

Answer 6

Bacteria:
Prokaryotic
Can form spores - protect DNA allowing continued reproduction

Question 7

Describe the characteristics of algae, giving examples

Answer 7

Algae:
Photosynthetic
e.g. Seaweed - a source of hydro-colloids - used as thickeners, stabilizers and gelling agents
e.g. Toxigenic algae - produce toxins passed onto shellfish

Question 8

Describe the characteristics of archaea, giving examples

Answer 8

Archaea:
Prokaryotic
Often extremophiles
e.g. Pyrococcus - contains amylase that can function at 100 degrees

Question 9

Describe the characteristics of fungi

Answer 9

Fungi:
Moulds, yeasts and mushrooms
Non-photosynthetic
Filamentous
Toxigenic, filamentous fungi can grow on dry foods with low pH

Question 10

Describe the characteristics of protozoa

Answer 10

Protozoa:
Motile - have flagella
Found in water
Reproduce in HOST not food

Question 11

Describe the characteristics of virus’s

Answer 11

Virus:
Survive and reproduce in host cells
Extremely small - 15.25 nm in diameter

Question 12

What is meant by microbial growth?

Answer 12

Microbial growth - increase in cell mass

Question 13

Describe means of prokaryotic reproduction

Answer 13

Binary fission - 2 new daughter cell receive a complete set of chromosomes

Question 14

Define growth rate

Answer 14

Growth rate - change in population size per unit time

Question 15

What is meant by generation time?

Answer 15

Generation time - time needed for cells to divide into 2/double

Question 16

Describe lag phase

Answer 16

Acclimatization
No pop. increase
Enzyme synthesis

Question 17

Describe log/exponential growth phase

Answer 17

Maximum growth rate
Pop doubles per unit time
Either BALANCED or UNBALANCED growth occurs
On solid media colonies begin to appear.
In liquid broth, it becomes turbid - can be measured using a spectophotometer

Question 18

What is the difference between balanced and unbalanced growth?

Answer 18

Balanced growth = all cell constituents are synthesized at constant rates
Unbalanced growth = cell constituents are synthesized at different rates

Question 19

Describe the stationary phase

Answer 19

Microbes begin to die - nutrients and O2 concentration decreases
Toxic waste accumulates
No net gain in pop

Question 20

What are the 3 different temperature dependent microbes?

Answer 20

Psychrophiles - grow at very cold temps.
Mesophiles - grow at average temps.
Thermophiles - grow at very warm temps.

Question 21

Describe psychrophiles, give an example

Describe their cell membrane

Answer 21

15 degree optimun
Active at cool temps
Membrane - have a high concentration of unsaturated F.A
e.g. Streptococci

Question 22

Describe mesophiles, give examples

Answer 22

39 degree optimun
48 degree maximum
e.g. E-coli, Staphylococcus

Question 23

Describe thermophiles, give examples

Answer 23

45-80 degree optimum
Mainly prokaryotes
Membranes have a high concentration of saturated fatty acids

Question 24

What is the optimum, minimum and maximum pH for a neutophile?

Answer 24

Optimum - pH 7
Minimum - pH 5
Maximum - pH 9

Question 25

How do acidophiles and alkalphiles maintain their pH?

Answer 25

Maintianing pH:
Proton-ion exchange mechanisms
Synthesising proteins which provide protection

Question 26

Define aerobes

Answer 26

Aerobes - tolerate O2 content HIGHER than in air (21%)

Question 27

Define facultative anaerobe

Answer 27

Facultative anaerobe - can grow with or without O2

Prefer aerobic growth

Question 28

Define microaerophiles

Answer 28

Microaerophiles - grow at lower O2 content than in air

Question 29

Define Aerotolerant anaerobe

Answer 29

Aerotolerant anerobe - grow in the presence of O2 but do not use it

Question 30

Define Obligate anaerobe. Give examples

Answer 30

Obligate anaerobe - killed by O2 e.g.cl. perfringens and botulinum

Question 31

What enzymes do aerobes produce for protection against reactive O2?

Answer 31

Catalase, SOD

Question 32

What is the difference between barotolerant and barophillic microbes?

Answer 32

Barotolerant - tolerate high pressures but are adversely affected by them
Barophillic - grow more rapidly at high pressures

Question 33

How does ionizing radiation affect microbes?

Answer 33

Degrades DNA, causing microbial death

Question 34

How does UV radiation affect microbes?

Answer 34

Breaks DNA - microbial death

used for disinfection

Question 35

Why might bacteria be UV tolerant?

Answer 35

UV tolerant bacteria contain carotenoid pigments

Question 36

Describe osmotolerant microbes

Answer 36

Grow at a wide range of aw

Use solute molecules in metabolism to maintain their own osmotic concentration

Question 37

How many colonies should a dilutent dilute microbes to?

Answer 37

30-300 colonies

Question 38

Describe autoclaving

Answer 38

Autoclaving - 121 degrees at 15 psi for 15 mins
High temperature and pressure used to destroy micro-organisms
Autoclave tape appears with a black line after autoclaving

Question 39

Describe filtration. How effective is it?

Answer 39

A filter is used to remove liquid or gas
e.g. a member and HEPA filter is used in a laminar flow cabinet to sterilize air
Filtration does NOT remove VIRUSES from air

Question 40

What are the 3 routes of infection?

Answer 40

oral
dermal
inhalation - aeresols inhaled from broth culture

Question 41

What is used to add fresh medium in continuous culture?

Answer 41

Chemostat - adds fresh medium