Microbiology and ID

Question 1

What are the 3 main magnifying instruments? Which is the best?

Answer 1

Compound light microscope - very basic but can use living cells
Transition electron microscope - best resolution but can’t use living cells
Scanning electron microscope - not great resolution but produces 3D images

Question 2

What are bacteria?

Answer 2

Prokaryotes
Lives freely in the environment
Classified as spherical, rod shaped or spiral
Rapidly multiply

Question 3

What are viruses?

Answer 3

Bacteriophage, influenza etc, they cause disease in other organisms.
Outer envelope with an inner protein (DNA/RNA)
Very small
Reproduce inside the cell they infect

Question 4

What are eukaryotes?

Answer 4

Can be protists:
Algae - mainly aquatic and carry out photosynthesis
Protozoa - unicellular, no cell wall, membranous, visible structures, mainly aquatic, no chlorophyll

Or fungi: good for the environment (food, antibiotics, fermentation) and can be uni or multicellular, no many cause disease

Or microscopic parasites: roundworms, tapeworms, flukes etc. Usually target GI

Question 5

What shapes can bacteria come in?

Answer 5

Coccus (round)
Bacillus (rod)
Spiral

Coccobacillus (squished rod) and vibrio (bent rod)

Question 6

What is the slime layer?

Answer 6

A capsule containing polysaccharides that helps avoid phagocytosis and binds to surfaces

Question 7

What are main components of bacteria and their function?

Answer 7

Flagella - aids movement
Fimbrae - projections to help cause disease by attaching to cells
Pilli - same as fimbrae but also form bacterial conjugation
Capsule - outermost layer
Plasma membrane - innermost layer, phospholipid bilayer
Cell wall - complex semi rigid structure, used to dictate in gram stains
Ribosomes - protein synthesis
Circular DNA - genetic material
Plasmid - additional genetic info that can be transferred

Question 8

What stains does gram staining use?

Answer 8

Crystal violet, them iodine treatment, alcohol to decolourise, then saffronin

Question 9

Why do bacteria take up gram staining differently?

Answer 9

Some cell walls have a thick peptidoglycan layer above the phospholipid bilayer, these stain purple
Others have a thin peptidoglycan layer in between two phospholipid bilayers, this stains pink

Question 10

Are bacteria uni or multicellular organisms?

Answer 10

All bacteria are prokaryotes and all prokaryotes are single celled

Question 11

Bacterial growth is defined by increase in cell number not size. How do bacteria reproduce?

Answer 11

Binary fusion

Question 12

What is the process of binary fusion?

Answer 12

DNA replicates
DNA divides
Transverse septum forms
Daughter cells separate

Question 13

What are the 4 stages of growth in culture?

Answer 13

Lag phase - acclimatising to the new medium
Log phase - optimum growth phase, exponential growth by binary fusion
Stationary phase - plateaus as nutrients exhausted / waste accumulation
Death phase - excess accumulation of waste / lack of nutrients

Question 14

What are the 4 main requirements for growth?

Answer 14

Temperature, pH, oxygen (or lack of) and water / osmotic pressure

Question 15

What are the 4 categories bacteria can be divided into based on optimum temperature?

Answer 15

Psychrophiles - 10’c
Mesophiles - 25-35’c
Thermophiles - 60’c
Extreme thermophiles - 80+’c

Question 16

What are the 3 categories bacteria can be classified as depending on their optimum pH?

Answer 16

Acidophiles - 0-6
Neutrophiles - 6-9
Alkalophiles - 9-14

Question 17

What are the 6 categories bacteria can be classified as depending on their optimum O2 requirements?

Answer 17

Obligate aerobes - requires O2
Facilitative anaerobes - with or without, better in O2
Aerotolerant anaerobes - equally with or without O2
Obligate anaerobes - die in presence of O2
Microaerophiles- requires 2-10% O2
Capnophiles - requires CO2 to grow