Bacterial Growth and Counting Bacteria

Question 1

Binary Fission

Answer 1

• How prokaryotic cells divide
• Mitosis is unnecessary because there is only one chromosome
• Chromosomes replicates and cell divides into two equal cells

Question 2

Budding

Answer 2

• Alternate form of cell division
• Chromosome replicates and smaller daughter cell buds off
• Small cells then grows to full size

Question 3

Direct Count

Answer 3

• Use a Petroff-Hauser Chamber: special slide with microscopic grid
• Includes both living and dead cells
• Very difficult with cells that move

Question 4

Spectrophotometer

Answer 4

• Used to determine cell concentration

- Also counts dead cells

Question 5

Viable Count

Answer 5

• Most accurate method
• Make serial dilutions, plate dilutions, and wait for growth
• Count colonies: only counts viable cells

Question 6

Quorum Sensing

Answer 6

As the density of a population of bacteria increases, the bacteria can take on new characteristics. E.G. non-pathogenic at low conc. but pathogenic at high conc.
Allows cells to communicate

Question 7

Mechanism for Quorum Sensing

Answer 7

Cells produce chemical X and have a receptor for X. While few cells are present [X] is low so it does not bind. When many cells are present [X] is high and it binds to the receptor giving new traits to the cell