Question

Answer needs to be 150 words or more.

---Contrast direct and indirect methods of measuring bacterial growth and discuss the limitations of each method

Answer 1

Measuring bacterial growth:
1. Direct methods:
i. Plate counts
Advantages: Measures viable cells
Disadvantage: We need to perform serial dilutions and grow bacteria on plates (incubation period of 12 hrs)

ii. Direct microscopic count
Advantages: Gives a direct count
Disadvantages: We can not always distinguish live vs dead. Motile bacteria are difficult to count.

iii. Filtration
iv. Most probable number

2. Indirect methods:
i. Turbidity
As bacteria grow in the culture, the turbidity increases which can be used measured using the spectrometer.
Advantages: Rapid
Disadvantages: No distinguishment between live vs dead cells
ii. Dry weight
Cells are pelleted and weighed.
Advantages: Rapid
Disadvantages: No distinguishment between live vs dead cells. It gives an approximate value.

iii. Metabolic activity