Lecture 2 & 3

Question 1

Thermophilic bacteria

Answer 1

Grow at > 50 degrees or above

Question 2

Psychrotrophic bacteria

Answer 2

Grow at refrigeration temperature (<5 degrees)

Question 3

Thermoduric bacteria

Answer 3

Able to survive pasteurisation

Question 4

Halotolerant bacteria

Answer 4

Able to survive high salt concentration (>10 degrees)

Question 5

Aciduric bacteria

Answer 5

Able to survive at low pH (<4)

Question 6

Osmophilic bacteria

Answer 6

Able to grow at relatively high osmotic environment

Question 7

Gas producing bacteria

Answer 7

Produce gas during metabolism of nutrients

Question 8

Slime producers

Answer 8

Produce slime because of their ability to produce extracellular polysaccharides

Question 9

Spore formers

Answer 9

Ability to produce spores e.g. bacillus sp

Question 10

Aerobes

Answer 10

Require oxygen to grow

Question 11

Anaerobes

Answer 11

Cannot grow in the presence of oxygen

Question 12

Facultative anaerobes

Answer 12

Can grow both at the presence and absence of oxygen

Question 13

Coliforms

Answer 13

Gram -ve, non-motile, facultative anaerobic bacterium. Usually associated with enteric system of mammals

Question 14

Faecal coliforms

Answer 14

Coliforms strictly associated with enteric systems of mammals e.g. e.coli

Question 15

Enteric pathogens

Answer 15

Pathogens of gastrointestinal tract of mammals

Question 16

microbial growth: Binary division

Answer 16

1. Duplication of chromosome
2. Continued growth of cell
3. Division into two cells

Question 17

Microbial growth: Budding

Answer 17

1. Mother cell
2. Bud develops at one end
3. Develop into new cells
4. Growth of the cell
5. New cells

Question 18

Bacteria growth

Answer 18

1. Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly towards the other end of the cell
2. Replication continues. One copy of the origin is now at each end of the cell
3. Replication finishes. Plasma membrane grows inward, and new cell wall is deposited
4. Two daughter cells result

Question 19

Fungi growth

Answer 19

Spores (asexual reproduction)

Question 20

Viruses replication

Answer 20

1. Attachment - the phage attaches to the surface of the host
2. Penetration - the viral DNA enters the host cell
3. Biosynthesis - phage DNA replicated and phage proteins are made
4. Maturation - new phage particles are assembled
5. Lysis - the cell lyses, releasing the newly made phage

Question 21

Microbial growth curve

Answer 21

Lag phase, exponential growth phase, stationary phase, death phase

Question 22

Kinetics of microbial growth; Biomass concentration

Answer 22

X (g/L or g/Kg) function of time

Question 23

Kinetics of microbial growth; Growth rate

Answer 23

• Growth rate constant, u, is a function of the substrate concentration, S
• Um is the maximum growth rate (the rate at which the substrate concentration is not limiting)

Question 24

Generation time

Answer 24

G = 0.3t / (Log10z - log10x)

G= generation time (min) or td(h)
0.3 = constant value of log102 (doubling)
t = duration of the study (min/h)
x = initial number of cells/biomass
z = final number of cells/biomass