Broth Culture: Definition, Medium & Characteristics

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: The Environment, Levels of Ecology and Ecosystems

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:04 What Is Broth Culture?
  • 0:42 Why Are Broth Cultures Used?
  • 1:26 Broth Culture Bacteria…
  • 2:13 Broth Culture Medium
  • 3:35 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Bridgett Payseur

Bridgett has a PhD in microbiology and immunology and teaches college biology.

Expert Contributor
Shelby DeVore

Shelby has a BS in Animal Science and a MS in Agriculture and Natural Resources. She taught high school and college animal science and biology courses for over 5 years.

Broth cultures are used by scientists to grow bacteria. Learn why broth cultures are used, some characteristics of bacteria in broth cultures, and the different types of media available.

What Is Broth Culture?

What do you think of when you hear the word broth? Probably a flavorful liquid made from chicken, beef, or veggies and used as a base for soups, right? Bacteria and other microbes, like yeast, can be cultured in broth. It's not the same broth you'd find in your soup, but it has similarities.

Broth cultures are liquid cultures used to grow bacteria in laboratories. To create a broth culture, a scientist begins with a sterile liquid growth medium. The medium is inoculated with bacteria and placed in an incubator at the appropriate temperature. After a certain amount of time has passed, the broth becomes cloudy from the increased number of microbes.

Why Are Broth Cultures Used?

Why would a scientist choose to use a broth culture over agar? Broth cultures are convenient for growing a large number of bacteria very quickly. Scientists use these bacteria for other tests, combine them with freeze-medium for long-term storage, or inoculate them into other media for further experimentation.

Broth cultures are basically a way for scientists to grow and maintain their cultures of bacteria. They're also useful for bacteria that have been in a stressful experiment. It's hard to think of bacteria being stressed, but some experiments involve subjecting bacteria to harsh conditions like high heat. After the experiment, the bacteria can recover in a highly nutritious broth culture. It's a similar concept to an athlete going in a hot tub after a grueling football game.

Broth Culture Bacteria Appearance

You might think that bacteria in a broth culture are suspended equally throughout, like a well-blended soup. However, different bacteria behave differently. Some bacteria may remain dispersed evenly; others may clump together at the bottom of the culture or form a layer on top of the broth. Mostly, the bacteria's location has to do with whether or not the bacteria need oxygen. There are three different types:

  1. Aerotolerant anaerobic bacteria are evenly dispersed throughout the culture. While they don't require it, oxygen isn't poisonous to them, and they can live anywhere in the culture.
  2. Obligate anaerobic bacteria can't survive in the presence of oxygen, so they clump together at the bottom of the culture.
  3. Aerobic bacteria, which require oxygen to live, form a layer at the top of the medium. This allows them to be as close as possible to the oxygen source.

Broth Culture Medium

The growth medium is the liquid that the bacteria is grown in. Luria broth (LB broth), also called lysogeny broth or Luria-Bertani broth, is among the most common media for broth cultures. It was developed in the 1950s, primarily for growing Eschericia coli bacteria. It's used to help allow the bacteria to grow. LB broth is an undefined medium. Growth media can be defined by several other categories:

To unlock this lesson you must be a Member.
Create your account

Additional Activities

Research Prompts

Research Prompt 1

In the lesson, you learned that there are various types of media that can be used to grow bacteria. Research three types of defined broth media.

  • What are three types of defined broth media?
  • How are different types of defined broth media made?
  • Are they best suited for different types of bacteria?

Research Prompt 2

Defined media has measured amounts of ingredients, while undefined media has some variation to some of the ingredients. Research defined and undefined media.

  • Is one of them better than the other?
  • Can they be used interchangeably?
  • Is one better suited to certain bacteria than others?

Research Prompt 3

Aerotolerant anaerobic bacteria are evenly dispersed throughout the broth culture.

  • What are some examples of aerotolerant anaerobic bacteria?

Anaerobic bacteria clump together at the bottom of the broth as oxygen can be toxic to them.

  • What are some examples of anaerobic bacteria?

Aerobic bacteria form a layer at the top of the medium, so they can be closer to the oxygen source.

  • What are some examples of aerobic bacteria?

Research Prompt 4

Luria broth is referred to frequently throughout the lesson. Research the broth further.

  • How is luria broth made?
  • What characteristics makes it so popular?
  • Are there other nutrient broths that perform as well as Luria broth?

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account