MicrobiologyLesson 1 of 2 in the course Control of Microbial Growth

Physical Methods for Microbial Control: Heat, Cold, Pressure, Radiation, and Filtration

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Heat is one of the oldest and most widely used ways to control microorganisms. This lesson explains how heat damages cells and how laboratories use different heating methods to achieve sterilization.

Heat can damage microbial membranes and denature proteins, disrupting the structures and processes cells need to survive. The effect depends on both the temperature and the time of exposure. Some organisms, especially endospore-formers such as Clostridium botulinum, are more heat resistant than vegetative cells.

All flashcards

What is thermal death point (TDP)?
The lowest temperature at which all microbes in a sample are killed in a 10-minute exposure.
What is thermal death time (TDT)?
The time required to kill all microbes in a sample at a specified temperature.
What does autoclave tape indicate?
It shows that a temperature threshold was reached, but does not prove adequate exposure time or sterility.
What is desiccation?
Removal of water to inhibit microbial growth; some microbes may survive and recover when moisture returns.
What is water activity?
The amount of water available in a food or material for microbial use.

Quiz questions

  1. What temperature and exposure time are used for HTST milk pasteurization?Answer: 72 °C for 15 seconds.
  2. Which statement describes a limitation of high-pressure processing (HPP)?Answer: It can inactivate many vegetative microbes, but endospores may survive.
  3. What DNA damage can ultraviolet light cause in microbes?Answer: It can make adjacent thymine bases bond to form thymine dimers.
  4. Which protection does a Class II biological safety cabinet provide?Answer: Protection for personnel, the environment, and the product.
  5. What is a limitation of a 0.2-µm membrane filter used to remove bacteria from liquid?Answer: Many viruses are small enough to pass through it.

Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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