Lab 2

Question 1

What are the safety guidelines for lab 2?

Answer 1

Treat E. coli cautiously. Do not touch personal belongings with contaminated gloves and if spilled, alert TA immediately and disinfect area with 70% ethanol.

Question 2

Under which conditions does E. coli grow best?

Answer 2

Nutrient-rich broth culture (ex. LB)
37 degrees celsius
continuous shaking

Question 3

What does shaking E coli do?

Answer 3

Shaking the culture provides fresh oxygen to the cells while facilitating exchange of nutrients and waste products

Question 4

Under optimal conditions, when will E coli be fully grown

Answer 4

overnight incubation (12-16 hours)

Question 5

What does a fully grown E coli culture look like?

Answer 5

Opaque

Question 6

What is maximum absorbance in bacterial broth around?

Answer 6

590 nm

Question 7

How can we estimate the number of cells in a culture?

Answer 7

Using absorbance spectroscopy.

Question 8

What are the three phases of E. coli growth?

Answer 8

Lag phase, log phase, stationary phase

Question 9

What is the lag phase of E. coli growth?

Answer 9

No growth (or very little) following inoculation as bacteria acclimate to their environment.

Question 10

What is the log phase of E. coli growth?

Answer 10

Exponential growth; reaches maximum growth rate during this period.

Question 11

What is the doubling time of E. coli?

Answer 11

20-25 minutes

Question 12

What is the stationary phase of E. coli growth?

Answer 12

Bacteria stop dividing as resources are depleted and waste accumulates.