---
title: "Brain Heart Infusion | Microbiology"
description: "Brain heart infusion is a nutrient-rich culture medium in Microbiology used to grow fastidious bacteria and fungi, including organisms needing extra nutrients."
canonical: "https://fiveable.me/microbio/key-terms/brain-heart-infusion"
type: "key-term"
subject: "Microbiology"
unit: "Unit 9"
---

# Brain Heart Infusion | Microbiology

## Definition

Brain heart infusion is an enriched growth medium in Microbiology made from brain and heart extracts plus nutrients like peptones and dextrose. It supports fastidious microbes that will not grow well on basic media.

## What It Is

Brain heart infusion, or BHI, is an enriched culture medium in Microbiology that gives microorganisms extra nutrients so they can grow better than they would on basic media. You will usually see it as brain heart infusion broth or brain heart infusion agar, depending on whether the medium is liquid or solid.

The reason it works is simple: some microbes are fastidious, meaning they have demanding nutritional needs. They may need amino acids, peptides, vitamins, and other growth factors that ordinary media do not supply in enough quantity. BHI is made to fill those gaps. It contains infusions from calf brain and beef heart, along with peptones, dextrose, sodium chloride, and other ingredients that create a nutrient-dense environment.

In practice, BHI is used when a lab wants to recover organisms that are hard to culture or keep them growing under supportive conditions. Because it is so rich, it can support many bacteria, including aerobic and anaerobic species, and it can also support fungi in the right setup. That makes it a useful general enriched medium when the goal is recovery and maintenance rather than selecting for one organism.

BHI broth and BHI agar do the same basic job, but they are used a little differently. Broth is better when you want a liquid culture that can spread evenly through the medium, while agar gives you colonies you can isolate and inspect. If a microbiology lab is trying to grow a pathogen from a sample, BHI may be one of the first media chosen because it boosts the chance that a weak or picky organism will actually appear.

One common misconception is that BHI is selective. It is not. It does not block most microbes from growing the way selective media do. Instead, it adds nutrition, which makes it an enriched medium rather than a selective one.

## Why It Matters

Brain heart infusion shows up whenever Microbiology moves from simply naming a microbe to actually growing and observing it. If an organism will not grow on standard nutrient agar, BHI gives you a way to recover it, maintain it, or prepare it for later tests.

That matters because many course activities depend on culture growth before you can identify anything else. Colony appearance, hemolysis comparisons, oxygen requirements, contamination checks, and downstream biochemical testing all depend on having a healthy culture in the first place. If the medium is too poor, the result can look like a negative sample when the real problem is just bad growth conditions.

BHI also helps you compare media types. When you see BHI next to nutrient agar, blood agar, chocolate agar, or selective plates, you are being asked to notice what each medium adds or restricts. BHI is the enriched, supportive option. It is the medium you reach for when the organism needs extra help, not when you want to limit growth to one group.

In lab interpretation, that difference matters. A good culture on BHI can tell you the organism was alive and able to use the nutrients provided, while weak or no growth can point to a mismatch between the organism and the medium. That is a basic microbiology reasoning move: match the growth medium to the organism’s needs, then read the growth result in that context.

## Connections

### [Enriched Media](/microbio/key-terms/enriched-media)

BHI is a classic example of enriched media because it starts with a nutrient base and adds extra components that support picky organisms. When you see enriched media in Microbiology, think of media designed to grow fastidious microbes that cannot handle simpler plates well. BHI fits that pattern by supplying more available nutrients rather than restricting growth.

### [Fastidious Organisms](/microbio/key-terms/fastidious-organisms)

Fastidious organisms are the reason BHI exists in the first place. These microbes need specific nutrients or growth factors, so ordinary media may give weak growth or none at all. BHI gives them a richer environment, which is why it is useful for recovery and maintenance of organisms that are difficult to culture.

### [Blood Agar](/microbio/key-terms/blood-agar)

Blood agar is also enriched, but it is used for a slightly different purpose. It supports growth and can show hemolysis patterns, which makes it useful for identifying some bacteria based on how they affect red blood cells. BHI is richer in general and is more about supporting growth than showing that kind of visual reaction.

### [Brain Heart Infusion Broth](/microbio/key-terms/brain-heart-infusion-broth)

Brain heart infusion broth is the liquid form of the same medium. You would use broth when you want to grow microbes in suspension, build up biomass, or prepare a culture before transferring it to another test. The agar version is better when you need isolated colonies, but both rely on the same nutrient-rich base.

## On the AP Exam

A quiz question might give you a list of media and ask which one would best support a fastidious bacterium. That is where you identify BHI as an enriched medium, not a selective one. In lab practicals, you may also need to tell whether a plate or tube is BHI by recognizing that it is used for heavy growth, recovery, or maintenance rather than inhibition.

If you get a scenario about a microbe that refuses to grow on simple media, BHI is one of the first choices you should consider. The key move is to match the medium to the organism’s nutritional needs and explain why the richer ingredients matter. For short-answer or discussion questions, use the terms enriched medium, fastidious organism, broth, and agar correctly so your reasoning is clear.

## brain heart infusion vs Nutrient Agar

Nutrient agar is a general-purpose medium, while brain heart infusion is enriched. Both can grow many microbes, but BHI has extra nutrients that make it better for fastidious organisms. If a question asks which medium to use for a picky or hard-to-grow microbe, BHI is the stronger choice.

## Key Takeaways

- Brain heart infusion is an enriched microbiology medium used to grow organisms that need extra nutrients.
- BHI comes in broth and agar forms, so you can use it for liquid culture or for colony growth on plates.
- It supports fastidious bacteria and can also support fungi and anaerobic organisms under the right conditions.
- BHI is not selective, so it boosts growth instead of blocking unwanted microbes.
- When you see BHI in a lab question, think recovery, maintenance, and nutrient support.

## FAQs

### What is brain heart infusion in Microbiology?

Brain heart infusion is an enriched growth medium made to support microbial growth, especially for fastidious organisms. It contains brain and heart extracts plus nutrients like peptones and dextrose, which gives microbes more to use than a basic medium does.

### Is brain heart infusion selective or enriched?

It is enriched, not selective. BHI adds nutrients to help organisms grow, but it does not suppress most other microbes the way selective media do. That is why it is useful when recovery matters more than isolation.

### What is brain heart infusion broth used for?

Brain heart infusion broth is the liquid version of BHI. Microbiology labs use it to grow organisms in suspension, expand a culture, or keep a fastidious microbe alive under supportive conditions before further testing.

### How is brain heart infusion different from nutrient agar?

Nutrient agar is a basic general-purpose medium, while brain heart infusion is richer and better for demanding microbes. If an organism grows poorly on nutrient agar, BHI may give it the extra nutrients it needs to grow well.

## Related Study Guides

- [9.6 Media Used for Bacterial Growth](/microbio/unit-9/6-media-bacterial-growth/study-guide/7QLOcV9AAJUXfBX5)

## About This Document

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