Microbio Lab 22

What is the relationship between wavelength and energy?

Shorter wavelength = higher energy; longer wavelength = lower energy

What type of radiation includes gamma rays and X-rays?

Ionizing radiation

What type of radiation includes UV light?

Non-ionizing radiation

Why are gamma rays effective for sterilization?

They cause direct, complete DNA breakage and penetrate most materials

Why must bacteria be directly exposed to UV light to be killed?

UV light cannot penetrate paper, glass, or plastic

Which type of UV light is bactericidal?

UV-C (100–280 nm)

What DNA damage does UV-C cause?

Pyrimidine dimers, such as thymine dimers

What is a thymine dimer?

A covalent bond between two adjacent thymine bases, distorting DNA

Why do thymine dimers kill bacteria?

They prevent DNA replication and transcription

Which organism is expected to be most sensitive to UV radiation?

E. coli

Why is 5-day Bacillus subtilis more UV-resistant than 24-hour B. subtilis?

Older cultures contain more endospores, which resist UV damage

What key feature of Bacillus makes it UV-resistant?

Ability to form endospores

What is an epidemic?

A sudden or simultaneous outbreak or increase in disease cases in a community

Give two examples of epidemics

Polio (1950s), HIV/AIDS, H1N1 influenza

What is one way an infectious disease can be transmitted?

Ingestion, inhalation, sexual contact, direct contact, vector bites, or blood exposure

What type of transmission is simulated in this lab?

Direct contact or contaminated object (fomite) transmission

What is a fomite?

A contaminated object that can transmit infection

What is a common source epidemic?

An outbreak where many people are infected at once from a single source

What is an example of a common source epidemic?

Water contaminated after flooding in Pakistan

What is propagated transmission?

Person-to-person spread of disease

What is an index case?

The first infected individual in an epidemic

Which epidemic type involves rapid infection of many people all at once?

Common source epidemic

Which epidemic type spreads gradually through direct contact?

Propagated epidemic

Why is identifying the index case important?

It helps determine the origin and early transmission pathways of the outbreak