---
title: Growth in KCN (potassium cyanide)
description: "## About this test ### What is the purpose of the test?   This test determines whether the microbe can grow in a medium where potassium cyanide is present as a carbon and nitrogen source. ### How is growth in…"
url: "https://vumicro.com/docs/growth-in-kcn-potassium-cyanide/"
updated: "2022-11-01"
category: Reference Library / Biochemical tests
---

# Growth in KCN (potassium cyanide)

## About this test

### What is the purpose of the test?  

This test determines whether the microbe can grow in a medium where potassium cyanide is present as a carbon and nitrogen source.

### How is growth in KCN determined?  

If the microbe can grow in the presence of potassium cyanide , the broth will become turbid (cloudy) after incubation.

### What medium is used?  

The medium used is [Potassium Cyanide (KCN) broth](https://vumicro.com/docs/potassium-cyanide-kcn-broth/) , a nutrient medium with 0.75% potassium cyanide added.

### How is the test performed?  

An inoculum from a pure culture is transferred aseptically to a sterile tube of [KCN broth](https://vumicro.com/docs/potassium-cyanide-kcn-broth/).    The inoculated tube is incubated at 35-37 C for 24 hours. A positive test is indicated by the presence of turbidity.

### What reagents are added?  

None.

## Performing this test in the VUMIE Online lab

### Inoculation of Medium

1. Select the [potassium cyanide (KCN) broth](https://vumicro.com/docs/potassium-cyanide-kcn-broth/) medium.  

2. Complete the process of a [tube-to-tube aseptic transfer](https://vumicro.com/docs/perform-aseptic-transfers-tube-to-tube/) to inoculate the medium.

### Incubation of the Inoculated Medium

3. Place the inoculated tube into the 35-37 C incubator.  

4. Press the [New Day button](https://vumicro.com/docs/use-the-new-day-button/) to move forward 24 hours.

### Determination of Test Results

5. Incubate this test for only 24 hours.  

6. Retrieve the incubated culture from the incubator.

7. Observe test result. The test is positive if there is obvious turbidity in the tube. In negative tests, there is no growth.  

8. [Record test result](https://vumicro.com/docs/record-test-results/).  

[Uninoculated KCN broth](https://vumicro.com/wp-content/uploads/2022/07/cleybnnnnn-2018_07_01-17_21_39-UTC.jpg)

[Positive for growth on KCN](https://vumicro.com/wp-content/uploads/2022/07/cleybynnnn-2018_07_01-17_21_39-UTC.jpg)

[Negative for growth on KCN](https://vumicro.com/wp-content/uploads/2022/07/cleybnnnnn-2018_07_01-17_21_39-UTC.jpg)

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