Lab 4- Pure Culture and Growth Conditions

Growth Curve components

• Escherichia coli

• Focusing on the exponential phase to determine the
  generation time of the organism

2 ways to measure growth curve

1. Directly using dilutions and colony forming units/mL from plate count

2. Indirectly using turbidity of the culture measured with the spectrophotometer to determine Opitcal Density (OD)

Each colony represents…

1 cell that replicated over and over from the original culture

Generation Time (GT) Calculation

Use trendline to calculate GT
• Pick two points that are
double each other in
concentration
• The change in time between
those points is GT

Pure Culture

The type of culture most frequently used in the laboratory which contains only a single species of microorganism

Subculture

A second level culture where an isolated colony from one culture is taken and then transferred into a new medium

Mixed culture

A culture which contains two or more species

Contaminated Culture

A culture which contains one or more unwanted and often unidentified microbes.

Gas Pak

release hydrogen

Pink colored resazurin

indicates oxygen in medium

Sodium Thioglycollate

reduce oxygen in medium

Blue colored methylene blue strip

indicates oxygen in jar