Home » Colony Counter Principle, Types, Uses with Diagram

Colony Counter Principle, Types, Uses with Diagram

A colony counter is a device or software used to count the number of colonies of microorganisms in a culture plate. It can be used in microbiology and other fields to quantitatively assess the growth of microorganisms.

Colony Counter Definition

Taking a total microbial count, often called a total viable count, is a common practice in the fields of clinical, food, dairy, and pharmaceutical microbiology. It takes a lot of time, effort, and concentration to count bacterial colonies manually. 

Colony counter offers an alternative, long-term solution to this problem by making it easy to count colonies quickly and accurately. A colony counter is a piece of equipment used to count the number of microorganism colonies growing on agar plates. 

There are many kinds of colony counters that can quickly and accurately count bacteria and yeast colonies. Some of these colony are manually operated, while others are automatically operated.

Types of Colony Counter

There are many different kinds of colony counters, but they can be put into two main groups: manual and automatic.

Manual colony counters: In a manual colony counter, a grid is used to help the user keep track of how many colonies are located in a certain space. This method of counting colonies is cheap, but it takes a long time and can lead to mistakes.

Automated colony counters: Image analysis, optical scanning, and fluorescence imaging are only a few examples of the technology used by automated colony counters. Automated colony counters are often more expensive than manual colony counters; nonetheless, they are able to count huge numbers of colonies fast and precisely.

Colony Counter Diagram

Colony Counter Diagram

Figure 1: Colony Counter Diagram

Manual colony counters

In microbiology, manual colony counters are used to count how many colonies are in a petri dish. Most of the time, they have a magnifying glass, a grid or template, and a way to mark or count the colonies. This approach is extensively utilized despite widespread acknowledgement that it is both less efficient and more time-consuming than alternative approaches.

a. Manual Colony Counters Principle

b. Parts of the Manual Colony Counter

c. Manual Colony Counter Procedure

d. Manual Colony Counter Limitations

a. Working Principle

Each colony is identified by tapping the Petri dish with an automatic marking probe pen while the dish is resting on an electronic pressure pad under bright lights. The amount of pressure applied to the touch screen is reflected in the digital counter. The intensity of this stress can be adjusted as needed. It helps keep us from counting colonies twice by accident or missing any entirely. Wolfheugal graticule, segmentation disc, and centering adapters for 50-90mm plates are also included in the set of tools. In addition, there is an integrated averaging tool for counting numerous plates at once, a darkening background for clear colonies, and glare-free illumination for best viewing of outlying colonies.

b. Parts and Functions

Magnifying lens: This magnifying lens magnifies the colonies on the petri dish for precise counting or marking.

Grid or template: This grid or template is placed over the petri dish as a guide for counting or marking the colonies.

The Working Base: The platform that supports the petri dish and grid or template during counting or marking.

The Light Source: Some manual counters are provided with a built-in light source for improved viewing of the colonies.

Auto marker probe: Pen with built-in counter; presses against colony, emits audible beep, and transmits data to a nearby computer.

Manual colony counter diagram

Figure 2: Manual colony counter Image/Diagram

c. Working Procedure

Press the On/Off Switch to activate the device. Place the Petri dish on top of the glass grid. Remove the cap from the Pen and, while keeping the Pen straight, press firmly on the Petri dish containing the Bacteriological Colony. 

The Counter will record a number, emit a beep, and place a dot of ink on the Petri dish. Continue until all colonies have been counted in this manner. 

As each colony is marked with ink as it is tallied, it is impossible to overlook or double-count a colony. When no more numbers can be counted. Take note of the counter’s reading.

d. Instrument Limitations

Manual colony counters have several limitations, including: Time-consuming, Observer bias, Difficulty in distinguishing between colonies, Limited to small area and Inability to count colonies of different morphologies.

Automatic Colony Counters

Instruments called automatic colony counters are used in the field of microbiology to accurately tally the number of individual microbial colonies in a test tube or Petri dish. To speed up the counting process, they use cutting-edge tech including machine learning, and image processing. They usually include a camera, a light, and computer or software that can analyze the image and count the colonies.

a. Automatic Colony Counters Principle

b. Parts of Automatic Colony Counters

c. Automatic Colony Counters Procedure

d. Automatic Colony Counters Advantages

a. Working Principle

Document scanners, charge-coupled devices (CCD), digital cameras, webcams, and video equipment are just some of the digital image-capturing technologies that can be used to compile images for use in a computer-based system. Using software tools, it is possible to count colonies based on photographs of plates. Each plate is evaluated after being photographed. 

Using programmable image-processing software, the recorded photos are then converted to digital files on a computer. Separating and identifying any colonies is achieved through the use of single/multi-threshold segmentation methods. The objects and their contexts can look very different in automated systems. Usually, one of the three types of illumination can be chosen to improve visibility and boost precision.

They are: 1. Transmission technique: Applied to common, high contrast items with largely clear backgrounds. 2. Reflection technique: Used for objects with high contrast and opaque backgrounds. 3. Darkfield technique: For low-contrast, largely transparent objects.

b. Parts and Functions

Video 1: Automatic colony counter

Culture dish: The automatic counter can be used with many different types of culture dishes, such as those inoculated using a plate, a spiral, or any other method.

Light Source: Long-lasting LED lights power the automatic colony counter. Light sources and background colours can be combined four ways. Optional smart remote control multi-color light source background helps monitor culture media types and colours.

Imaging Tech: When counting artificial colonies, the old-school method involves using a magnifying glass with a magnification of three to six times to get a clear picture. More advanced CCD requirements are being implemented into automatic colony counter cameras. The current generation, the HCC-90A, boasts 5 million pixels, a colony resolution of 0.1mm, and a substantially sharper image.

Images Treatment: With its robust image processing capabilities, the automatic colony counter is a formidable tool. Background processing, colour marking, interference correction, colony expansion, area calculation, and similar features are not available on conventional colony counts.

Database: Automatic colony counters are better for database processing than traditional colony counters because they make it easier to store data, do smart queries, export data, etc.

c. Working Procedure

  1. Counting the colonies electronically by separating individual dark and light areas based on automatic or user-specified parameters and then counting the resulting areas of contrast. These counters are used to estimate the number of microorganisms in a liquid or product.
  2. Using sterile technique, one acceptable dilution or multiple acceptable dilutions within the predicted appropriate range are poured or spread on the agar plate, which is then incubated until individual colonies appear.
  3. Each colony shows where a single organism was first found. This means that the number of colonies on the plate is the same as the number of organisms in the volume of liquid spread across the plate. This concentration is then added to the known dilution of the original culture to get an idea of how many organisms were in the original culture.
  4. Depending on the size of the colony and the type of organism, it is possible to count between 100 and 300 colonies on a single plate. The colony counter must be able to count bacteria using the “spiral,” “spread,” “settle,” and “pour plates” methods.

d. Instrument Advantages

  1. Saves time
  2. Increases Speed
  3. Improves accuracy
  4. Standardises results
  5. Eliminates human error
  6. Heightens sensitivity
  7. Automatic data transfer
  8. Data traceability
  9. Complete audit trail


FAQs on Colony Counter

Place the petri dish on the platform of the digital colony counter. Adjust the focus and lighting to ensure that the colonies are clearly visible. Press the start button to begin counting. Use the device’s cursor or touch screen to mark each colony as it appears on the dish. The device will automatically keep a tally of the number of colonies counted. When you have finished counting, press the stop button to end the counting process. The final count will be displayed on the device’s screen.

Divide the petri dish into a grid pattern using a pen or marker. Examine the dish closely under a light source to ensure all colonies are visible. Use a counting chamber or grid to count the colonies in a specific area of the dish. Use a fine-tipped brush to transfer colonies to the counting chamber or grid. Count the number of colonies in each square of the grid and record the number. Repeat the process until all colonies on the dish are counted.

Use a manual or digital colony counter to count the colonies on the dish. Use a light source and a grid or counting chamber to ensure all colonies are visible and counted. Record the number of colonies counted. Compare the results with a digital colony counter and do a verification process if necessary.

Use a manual or digital colony counter to count the colonies on the dish. Use a light source and a grid or counting chamber to ensure all colonies are visible and counted. Record the number of colonies counted. Compare the results with a digital colony counter and do a verification process if necessary.

Use a manual or digital colony counter to count the colonies on the dish. Use a light source and a grid or counting chamber to ensure all colonies are visible and counted. Record the number of colonies counted. Compare the results with a digital colony counter and do a verification process if necessary.