Microbio Exam 2 - Short answer questions

Four Phases of Bacterial Growth

1. Lag Phase: bacteria ADJUST to their environment 

2. Log Phase: bacteria MULTIPLY 

3. Stationary Phase: new bacteria are being PRODUCED while others are dying 

4. Death Phase: more bacteria DIE than are being produced 

Factors Affecting Microbial Death

1. Number of microorganisms: MORE bacteria take longer to kill.

2. Type of microorganism: some are harder to kill than others. 

3. Organic material: Blood or dirt can make disinfectants less effective. 

4. Temperature: Warmer/higher temperatures can help some disinfectants work faster.

Most Difficult Microorganisms to Kill 

• Prions are infectious proteins

• Bacterial endospores survive harsh conditions including heat and many chemicals. 

define biofilm and understand its importance to bacterial growth and human health

Biofilm - A community of microorganisms that attach to a surface and are surrounded by protective sticky matrix. 

• They protect bacteria from disinfectants and some antibiotics.

• They make infections harder to eliminate.

• They can form on medical devices. 

What are the two types of operons and what do they do

• Inducible operon: usually OFF but turns ON when needed

• Repressible operon: usually ON but turns OFF when needed.

What is the difference between a Mutations & Mutagens

1. Mutation: A change in the DNA sequence of an organism. 

2. Mutagen: Something that causes mutations.