Lab 8 - Ionic composition

Question 1

Define non-halophiles. Which test microbe is one?

Answer 1

Evolved in environments with very low salinity = able to grow in media without salt and are inhibited by salt
Eg. E. coli

Question 2

Define halotolerant. Which test microbe is one?

Answer 2

Tolerate low to moderate salinity but also grow in its absence
Eg. S. aureus

Question 3

Define halophilic. Which test microbe is one?

Answer 3

Adapted to relatively high salinity and require salt for growth; inhibited by low salinity and very high salinity
Eg. V. harveyi

Question 4

Define extreme halophiles. Which test microbe is one?

Answer 4

Require very high salinity (15-30%) for growth and are inhibited by moderate salinity
Eg. H. salinarum

Question 5

How much salt (g) would you need to prepare 250mL agar with 8% salt?

Answer 5

8% = 8g salt per 250mL
8 x 250/100 = 20g

Question 6

Why does H. salinarum have pink cultures?

Answer 6

• Bacterioruberin in membrane
• Caroternoid pigment
• Protect against DNA damage from UV light by acting as an antioxidant to ROS produced by UV light

Question 7

Why is V. harveyi bioluminsecent?

Answer 7

Similar to V. fischeri, uses quorum sensing to produce bioluminscence via histidine kinase in membrane

Question 8

Describe the 2 methods used to distinguish bacteria in this experiment

Answer 8

For S. aureus, E. coli and V. harveyi
1. Mix colonies into 10mL specific solution to make them turbid (different for each bacteria)
2. Prepare serial dilutions in the same specific solution
3. Pipette dilutions onto agar plates with different NaCl concentrations
4. Incubate in specific conditions for each bacteria

For H. salinarum
1. Pipette drop of H. salinarum culture to broths with different NaCl concentrations
2. Incubate