What is colony counter and how it works? Definition Types, Principles and Uses

Colony Counter- Definition, Types, Working, Uses:

Colony Counter definition
  • A colony counter is an automatic device/instrument that is used to count colonies of bacteria or microorganisms present on the agar plates.
  • Colony Counters is a device that Counts the number of microorganisms on a petri dish
What is colony counter and how it works?
Image source: moonsung.kr

What is colony counter?

  • A colony counter is a digital display-type automatic bacteria testing instrument. 
  • With the help of colony counter counting is getting faster and more accurate.
  • Now with the advancement of science and technology, colony counting technology is becoming more and more perfect. 
  • The colony counter is composed of a counter, probe pen, counting pool, and other parts. 
  • The counter is carefully designed with a CMOS integrated circuit, and LED digital tube display, the character height is 13mm, clear and bright, and with the special probe pen, the counting is sensitive and accurate. 
  • In the counting tank with the black background, the fluorescent light is illuminated, and the colony contrast is clear, which is easy to observe.
  • It is widely used in food, beverage, medicine, biological products, cosmetics, sanitary products, drinking water, domestic sewage, industrial wastewater, and bacterial counts in clinical specimens.
  • This instrument can reduce the labor intensity of laboratory personnel, improve work efficiency, and improve work quality. 
  • It is widely used in epidemic prevention in inspection institutes, hospitals, daily chemical factories and laboratories of colleges and universities, and scientific research units.
  • There are two types of colony counters manual colony counters and automated colony counters.
  • Generally, for users who do not require high accuracy, manual or semi-automatic colony counters can be considered. 
  • The manual price is relatively cheap, a little better, it is semi-automatic with voice reading function, the magnification is above 3, this has been able to meet the counting requirements of most users. 
  • The fully automatic counter with a higher configuration is mostly used in the microbiology laboratory.

What is Colony in Microbiology?
A colony is a single or aggregated group of microorganisms that grows on a suitable medium and reproduces to a certain extent to form a population of daughter cells that are visible to the naked eye. The purpose of colony counting is ultimately to estimate the number of cells present based on their given ability to continue to grow and expand under certain conditions like temperature and the state of the nutrient medium.

How to operate a colony counter:

  1. Firstly inserts the probe into the probe socket on the colony counter.
  2. Now turn on the power switch, and the light in the counting cell will be on. 
  3. At the same time, the bright display in the display window indicates that counting is allowed.
  4. After that put the petri dish to be tested into the counting tank with the bottom up. 
  5. Count all the colonies one by one on the bottom of the petri dish with a probe pen. 
  6. At this time, the colony is marked with color, and the numbers in the display window are automatically accumulated.
  7. Check carefully with a magnifying glass to confirm that there are no missing points and that the counting is completed.
  8. The number in the display window is the number of colonies in the petri dish.
  9. Remove the petri dish after recording the numbers. Press the reset button to display the resume, ready for another Petri dish to count.

Precautions while using Colony Counter:
  • The colony counter should be placed in a flat and dry place.
  • Add dust cover on colony counter after use.
  • The colony counter should be protected from moisture, direct sunlight, acid and alkali erosion, etc.
  • Prevent bacterial culture from contaminating the counting pool.
  • When counting the colonies, the probe pen should not be tilted too much, and the number will be entered when you tap it gently until there is a sense of bouncing.
  • The colony counter and the probe pen should not be disassembled at will. 
  • Use purified water to clean magnifying glass and other surfaces and then wipe it with lens paper before use.

Colony Counter Uses:
  • The colony counter can determine the degree of food contamination, and can also be used to observe the procedure of bacterial contamination of food.
  • It is widely used in epidemic prevention in inspection institutes, hospitals, daily chemical factories and laboratories of colleges and universities, scientific research units,, etc.
  • It is widely used in food, beverage, medicine, biological products, cosmetics, sanitary products, drinking water, domestic sewage, industrial wastewater, and bacterial counts in clinical specimens.

Examples of Colony Counters:

  • Accuracy up by rotation method! 
  • This device accurately measures the number of colonies generated in the medium layer after culturing. The light source of this device has a structure that makes it difficult for light unevenness to occur, and the measurement method is less susceptible to light unevenness, so it is possible to measure even small colonies with high stability.
  • High-precision measurement is possible by automatically distinguishing and measuring overlapping colonies.
  • In addition to automatically extracting the area of ​​the petri dish, it also supports media with subtle changes in brightness.
  • By rotating the petri dish and capturing images from different angles, variations in the amount of light transmitted due to differences in colony shape can be absorbed, resulting in more stable measurements.
  • Accuracy is improved by rotating in increments of 60° and averaging 6 measurements
  • Different detection settings for large and small colonies
  • Using a 1.45-megapixel CCD camera, even minute colonies can be measured
  • The polar coordinate conversion method improves the measurement accuracy of the outer circumference of the Petri dish.

2. High-sensitivity automatic colony counter/zone analyzer ProtoCOL3 / ProtoCOL3HD:

  • Measure colonies with a diameter of 0.043 mm without missing a beat! Easy operation with touch panel and Japanese software
  • ProtoCOL3 / ProtoCOL3HD is a next-generation automatic colony counter/zone analyzer with unique functions and performance by incorporating new technology that is completely different from conventional equipment.
  • In addition, on-to-pour culture, spiral plater, inhibition circle measurement, fractionation petri dish, Ames test, etc. are now possible.
  • The adoption of a high-sensitivity CCD camera and red, green, and blue LED lampshades made it possible to measure colonies with a minimum diameter of 0.043 mm in a 90 mm Petri dish.
  • Excellent image analysis function and shape recognition function have greatly improved analysis accuracy.
  • It supports touch panels and Japanese software, so you can comfortably and efficiently realize high-level measurements.
  • By adopting a sliding door, measurements can be made under constant conditions without being affected by external light.
  • The minimum colony diameter for measurement is 0.043 mm and the minimum circle of inhibition diameter is 0.1 mm.
  • ProtoCOL3HD with an a5-megapixel camera has an inhibition circle accuracy of over 99%.
  • The option “Report Creator” supports various Excel report formats.

Frequently asked Questions on Colony Counter:

1. What is CFU?
Answer: Colony-forming units are called CFUs. The meaning of CFU is the number of colonies forming colonies, not equal to the number of bacteria. For example, if two identical bacteria are close to each other or stick together, then after culturing these two bacteria will form a colony, at this time it is 2 bacteria, 1CFU.

2. How to count when the total number of bacteria in public appliances is greater than 100
Answer: If the bacterial content in the sample is considered to be relatively high, it can be diluted. After different dilutions are inoculated and poured into nutrient agar plates, the colonies are counted, and the average number of colonies is selected between 30-300. The final result is calculated and reported under the requirements of the testing standard.

3. Which microorganisms are the plate counts suitable for?
Answer: It is usually used to determine the number of single-celled microorganisms such as bacteria, spores, and yeasts contained in a sample.

4. How many molds and yeast colonies are counted in the plate
Answer: In the counting of microorganisms, the number of colonies between 30 and 300 is generally selected for counting.

5. Determination of the total number of colonies, how to count these spots
Answer: If you look at the colony shape, it should be the same kind of bacteria, so it needs to be calculated regardless of the size. The number of bacteria on this plate is not particularly large, and it can be calculated. If you think it’s too much, you can try gradient dilution and reduce the number to a few dozen, and that’s fine.

6. How to do colony count?
Answer: The colonies should be counted with the help of a colony counter 

7. What is the role of a colony counter?
AnswerColony counters are used to estimate the density of microorganisms in liquid culture by counting individual colonies on an agar plate, slide, mini gel, or Petri dish.

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